Merge from Google internal for 3.4 release

38 files changed, 1471 insertions, 575 deletions

diff --git a/java/core/generate-test-sources-build.xml b/java/core/generate-test-sources-build.xml
index ab415db6..68951747 100644
--- a/java/core/generate-test-sources-build.xml
+++ b/java/core/generate-test-sources-build.xml
@@ -5,6 +5,7 @@
         <arg value="--proto_path=${protobuf.source.dir}"/>
         <arg value="--proto_path=${test.proto.dir}"/>
         <arg value="${protobuf.source.dir}/google/protobuf/unittest.proto"/>
+        <arg value="${protobuf.source.dir}/google/protobuf/unittest_proto3.proto"/>
         <arg value="${protobuf.source.dir}/google/protobuf/unittest_import.proto"/>
         <arg value="${protobuf.source.dir}/google/protobuf/unittest_import_public.proto"/>
         <arg value="${protobuf.source.dir}/google/protobuf/unittest_mset.proto"/>
@@ -40,4 +41,4 @@
         <arg value="${test.proto.dir}/com/google/protobuf/map_test.proto"/>
         <arg value="${test.proto.dir}/com/google/protobuf/map_initialization_order_test.proto"/>
     </exec>
-</project>
\ No newline at end of file
+</project>
diff --git a/java/core/src/main/java/com/google/protobuf/AbstractMessage.java b/java/core/src/main/java/com/google/protobuf/AbstractMessage.java
index b5043eb5..065fa1a9 100644
--- a/java/core/src/main/java/com/google/protobuf/AbstractMessage.java
+++ b/java/core/src/main/java/com/google/protobuf/AbstractMessage.java
@@ -32,6 +32,7 @@ package com.google.protobuf;
 
 import com.google.protobuf.Descriptors.EnumValueDescriptor;
 import com.google.protobuf.Descriptors.FieldDescriptor;
+import com.google.protobuf.Descriptors.FileDescriptor.Syntax;
 import com.google.protobuf.Descriptors.OneofDescriptor;
 import com.google.protobuf.Internal.EnumLite;
 import java.io.IOException;
@@ -162,7 +163,7 @@ public abstract class AbstractMessage
     }
     return hash;
   }
-  
+
   private static ByteString toByteString(Object value) {
     if (value instanceof byte[]) {
       return ByteString.copyFrom((byte[]) value);
@@ -170,7 +171,7 @@ public abstract class AbstractMessage
       return (ByteString) value;
     }
   }
- 
+
   /**
    * Compares two bytes fields. The parameters must be either a byte array or a
    * ByteString object. They can be of different type though.
@@ -181,7 +182,7 @@ public abstract class AbstractMessage
     }
     return toByteString(a).equals(toByteString(b));
   }
-  
+
   /**
    * Converts a list of MapEntry messages into a Map used for equals() and
    * hashCode().
@@ -212,7 +213,7 @@ public abstract class AbstractMessage
     }
     return result;
   }
-  
+
   /**
    * Compares two map fields. The parameters must be a list of MapEntry
    * messages.
@@ -223,13 +224,13 @@ public abstract class AbstractMessage
     Map mb = convertMapEntryListToMap((List) b);
     return MapFieldLite.equals(ma, mb);
   }
-  
+
   /**
    * Compares two set of fields.
    * This method is used to implement {@link AbstractMessage#equals(Object)}
    * and {@link AbstractMutableMessage#equals(Object)}. It takes special care
    * of bytes fields because immutable messages and mutable messages use
-   * different Java type to reprensent a bytes field and this method should be
+   * different Java type to represent a bytes field and this method should be
    * able to compare immutable messages, mutable messages and also an immutable
    * message to a mutable message.
    */
@@ -275,7 +276,7 @@ public abstract class AbstractMessage
     }
     return true;
   }
-  
+
   /**
    * Calculates the hash code of a map field. {@code value} must be a list of
    * MapEntry messages.
@@ -371,7 +372,7 @@ public abstract class AbstractMessage
     public String getInitializationErrorString() {
       return MessageReflection.delimitWithCommas(findInitializationErrors());
     }
-    
+
     @Override
     protected BuilderType internalMergeFrom(AbstractMessageLite other) {
       return mergeFrom((Message) other);
@@ -432,8 +433,12 @@ public abstract class AbstractMessage
         final CodedInputStream input,
         final ExtensionRegistryLite extensionRegistry)
         throws IOException {
+      boolean discardUnknown =
+          getDescriptorForType().getFile().getSyntax() == Syntax.PROTO3
+              ? input.shouldDiscardUnknownFieldsProto3()
+              : input.shouldDiscardUnknownFields();
       final UnknownFieldSet.Builder unknownFields =
-        UnknownFieldSet.newBuilder(getUnknownFields());
+          discardUnknown ? null : UnknownFieldSet.newBuilder(getUnknownFields());
       while (true) {
         final int tag = input.readTag();
         if (tag == 0) {
@@ -451,7 +456,9 @@ public abstract class AbstractMessage
           break;
         }
       }
-      setUnknownFields(unknownFields.build());
+      if (unknownFields != null) {
+        setUnknownFields(unknownFields.build());
+      }
       return (BuilderType) this;
     }
 
diff --git a/java/core/src/main/java/com/google/protobuf/AbstractMessageLite.java b/java/core/src/main/java/com/google/protobuf/AbstractMessageLite.java
index 99787fcc..24830c0a 100644
--- a/java/core/src/main/java/com/google/protobuf/AbstractMessageLite.java
+++ b/java/core/src/main/java/com/google/protobuf/AbstractMessageLite.java
@@ -36,7 +36,9 @@ import java.io.FilterInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.util.ArrayList;
 import java.util.Collection;
+import java.util.List;
 
 /**
  * A partial implementation of the {@link MessageLite} interface which
@@ -118,8 +120,13 @@ public abstract class AbstractMessageLite<
     }
   }
 
-  protected static <T> void addAll(final Iterable<T> values,
-      final Collection<? super T> list) {
+  // For binary compatibility
+  @Deprecated
+  protected static <T> void addAll(final Iterable<T> values, final Collection<? super T> list) {
+    Builder.addAll(values, (List) list);
+  }
+
+  protected static <T> void addAll(final Iterable<T> values, final List<? super T> list) {
     Builder.addAll(values, list);
   }
 
@@ -334,6 +341,25 @@ public abstract class AbstractMessageLite<
           + " threw an IOException (should never happen).";
     }
 
+    // We check nulls as we iterate to avoid iterating over values twice.
+    private static <T> void addAllCheckingNulls(Iterable<T> values, List<? super T> list) {
+      if (list instanceof ArrayList && values instanceof Collection) {
+        ((ArrayList<T>) list).ensureCapacity(list.size() + ((Collection<T>) values).size());
+      }
+      int begin = list.size();
+      for (T value : values) {
+        if (value == null) {
+          // encountered a null value so we must undo our modifications prior to throwing
+          String message = "Element at index " + (list.size() - begin) + " is null.";
+          for (int i = list.size() - 1; i >= begin; i--) {
+            list.remove(i);
+          }
+          throw new NullPointerException(message);
+        }
+        list.add(value);
+      }
+    }
+
     /**
      * Construct an UninitializedMessageException reporting missing fields in
      * the given message.
@@ -343,16 +369,20 @@ public abstract class AbstractMessageLite<
       return new UninitializedMessageException(message);
     }
 
+    // For binary compatibility.
+    @Deprecated
+    protected static <T> void addAll(final Iterable<T> values, final Collection<? super T> list) {
+      addAll(values, (List<T>) list);
+    }
+
     /**
-     * Adds the {@code values} to the {@code list}.  This is a helper method
-     * used by generated code.  Users should ignore it.
+     * Adds the {@code values} to the {@code list}. This is a helper method used by generated code.
+     * Users should ignore it.
      *
-     * @throws NullPointerException if {@code values} or any of the elements of
-     * {@code values} is null. When that happens, some elements of
-     * {@code values} may have already been added to the result {@code list}.
+     * @throws NullPointerException if {@code values} or any of the elements of {@code values} is
+     *     null.
      */
-    protected static <T> void addAll(final Iterable<T> values,
-                                     final Collection<? super T> list) {
+    protected static <T> void addAll(final Iterable<T> values, final List<? super T> list) {
       checkNotNull(values);
       if (values instanceof LazyStringList) {
         // For StringOrByteStringLists, check the underlying elements to avoid
@@ -360,25 +390,31 @@ public abstract class AbstractMessageLite<
         // TODO(dweis): Could we just prohibit nulls in all protobuf lists and get rid of this? Is
         // if even possible to hit this condition as all protobuf methods check for null first,
         // right?
-        checkForNullValues(((LazyStringList) values).getUnderlyingElements());
-        list.addAll((Collection<T>) values);
-      } else if (values instanceof Collection) {
-        if (!(values instanceof PrimitiveNonBoxingCollection)) {
-          checkForNullValues(values);
+        List<?> lazyValues = ((LazyStringList) values).getUnderlyingElements();
+        LazyStringList lazyList = (LazyStringList) list;
+        int begin = list.size();
+        for (Object value : lazyValues) {
+          if (value == null) {
+            // encountered a null value so we must undo our modifications prior to throwing
+            String message = "Element at index " + (lazyList.size() - begin) + " is null.";
+            for (int i = lazyList.size() - 1; i >= begin; i--) {
+              lazyList.remove(i);
+            }
+            throw new NullPointerException(message);
+          }
+          if (value instanceof ByteString) {
+            lazyList.add((ByteString) value);
+          } else {
+            lazyList.add((String) value);
+          }
         }
-        list.addAll((Collection<T>) values);
       } else {
-        for (final T value : values) {
-          checkNotNull(value);
-          list.add(value);
+        if (values instanceof PrimitiveNonBoxingCollection) {
+          list.addAll((Collection<T>) values);
+        } else {
+          addAllCheckingNulls(values, list);
         }
       }
     }
-
-    private static void checkForNullValues(final Iterable<?> values) {
-      for (final Object value : values) {
-        checkNotNull(value);
-      }
-    }
   }
 }
diff --git a/java/core/src/main/java/com/google/protobuf/CodedInputStream.java b/java/core/src/main/java/com/google/protobuf/CodedInputStream.java
index 3dfbcb0a..d6a941b1 100644
--- a/java/core/src/main/java/com/google/protobuf/CodedInputStream.java
+++ b/java/core/src/main/java/com/google/protobuf/CodedInputStream.java
@@ -34,8 +34,8 @@ import static com.google.protobuf.Internal.EMPTY_BYTE_ARRAY;
 import static com.google.protobuf.Internal.EMPTY_BYTE_BUFFER;
 import static com.google.protobuf.Internal.UTF_8;
 import static com.google.protobuf.Internal.checkNotNull;
-import static com.google.protobuf.WireFormat.FIXED_32_SIZE;
-import static com.google.protobuf.WireFormat.FIXED_64_SIZE;
+import static com.google.protobuf.WireFormat.FIXED32_SIZE;
+import static com.google.protobuf.WireFormat.FIXED64_SIZE;
 import static com.google.protobuf.WireFormat.MAX_VARINT_SIZE;
 
 import java.io.ByteArrayOutputStream;
@@ -372,6 +372,64 @@ public abstract class CodedInputStream {
     return oldLimit;
   }
 
+
+  private boolean explicitDiscardUnknownFields = false;
+
+  /** TODO(liujisi): flip the default.*/
+  private static volatile boolean proto3DiscardUnknownFieldsDefault = true;
+
+  static void setProto3DiscardUnknownsByDefaultForTest() {
+    proto3DiscardUnknownFieldsDefault = true;
+  }
+
+  static void setProto3KeepUnknownsByDefaultForTest() {
+    proto3DiscardUnknownFieldsDefault = false;
+  }
+
+  static boolean getProto3DiscardUnknownFieldsDefault() {
+    return proto3DiscardUnknownFieldsDefault;
+  }
+
+  /**
+   * Sets this {@code CodedInputStream} to discard unknown fields. Only applies to full runtime
+   * messages; lite messages will always preserve unknowns.
+   *
+   * <p>Note calling this function alone will have NO immediate effect on the underlying input data.
+   * The unknown fields will be discarded during parsing. This affects both Proto2 and Proto3 full
+   * runtime.
+   */
+  final void discardUnknownFields() {
+    explicitDiscardUnknownFields = true;
+  }
+
+  /**
+   * Reverts the unknown fields preservation behavior for Proto2 and Proto3 full runtime to their
+   * default.
+   */
+  final void unsetDiscardUnknownFields() {
+    explicitDiscardUnknownFields = false;
+  }
+
+  /**
+   * Whether unknown fields in this input stream should be discarded during parsing into full
+   * runtime messages.
+   */
+  final boolean shouldDiscardUnknownFields() {
+    return explicitDiscardUnknownFields;
+  }
+
+  /**
+   * Whether unknown fields in this input stream should be discarded during parsing for proto3 full
+   * runtime messages.
+   *
+   * <p>This function was temporarily introduced before proto3 unknown fields behavior is changed.
+   * TODO(liujisi): remove this and related code in GeneratedMessage after proto3 unknown
+   * fields migration is done.
+   */
+  final boolean shouldDiscardUnknownFieldsProto3() {
+    return explicitDiscardUnknownFields ? true : proto3DiscardUnknownFieldsDefault;
+  }
+
   /**
    * Resets the current size counter to zero (see {@link #setSizeLimit(int)}). Only valid for {@link
    * InputStream}-backed streams.
@@ -572,7 +630,7 @@ public abstract class CodedInputStream {
           skipRawVarint();
           return true;
         case WireFormat.WIRETYPE_FIXED64:
-          skipRawBytes(FIXED_64_SIZE);
+          skipRawBytes(FIXED64_SIZE);
           return true;
         case WireFormat.WIRETYPE_LENGTH_DELIMITED:
           skipRawBytes(readRawVarint32());
@@ -585,7 +643,7 @@ public abstract class CodedInputStream {
         case WireFormat.WIRETYPE_END_GROUP:
           return false;
         case WireFormat.WIRETYPE_FIXED32:
-          skipRawBytes(FIXED_32_SIZE);
+          skipRawBytes(FIXED32_SIZE);
           return true;
         default:
           throw InvalidProtocolBufferException.invalidWireType();
@@ -1064,12 +1122,12 @@ public abstract class CodedInputStream {
     public int readRawLittleEndian32() throws IOException {
       int tempPos = pos;
 
-      if (limit - tempPos < FIXED_32_SIZE) {
+      if (limit - tempPos < FIXED32_SIZE) {
         throw InvalidProtocolBufferException.truncatedMessage();
       }
 
       final byte[] buffer = this.buffer;
-      pos = tempPos + FIXED_32_SIZE;
+      pos = tempPos + FIXED32_SIZE;
       return (((buffer[tempPos] & 0xff))
           | ((buffer[tempPos + 1] & 0xff) << 8)
           | ((buffer[tempPos + 2] & 0xff) << 16)
@@ -1080,12 +1138,12 @@ public abstract class CodedInputStream {
     public long readRawLittleEndian64() throws IOException {
       int tempPos = pos;
 
-      if (limit - tempPos < FIXED_64_SIZE) {
+      if (limit - tempPos < FIXED64_SIZE) {
         throw InvalidProtocolBufferException.truncatedMessage();
       }
 
       final byte[] buffer = this.buffer;
-      pos = tempPos + FIXED_64_SIZE;
+      pos = tempPos + FIXED64_SIZE;
       return (((buffer[tempPos] & 0xffL))
           | ((buffer[tempPos + 1] & 0xffL) << 8)
           | ((buffer[tempPos + 2] & 0xffL) << 16)
@@ -1290,7 +1348,7 @@ public abstract class CodedInputStream {
           skipRawVarint();
           return true;
         case WireFormat.WIRETYPE_FIXED64:
-          skipRawBytes(FIXED_64_SIZE);
+          skipRawBytes(FIXED64_SIZE);
           return true;
         case WireFormat.WIRETYPE_LENGTH_DELIMITED:
           skipRawBytes(readRawVarint32());
@@ -1303,7 +1361,7 @@ public abstract class CodedInputStream {
         case WireFormat.WIRETYPE_END_GROUP:
           return false;
         case WireFormat.WIRETYPE_FIXED32:
-          skipRawBytes(FIXED_32_SIZE);
+          skipRawBytes(FIXED32_SIZE);
           return true;
         default:
           throw InvalidProtocolBufferException.invalidWireType();
@@ -1429,7 +1487,9 @@ public abstract class CodedInputStream {
       final int size = readRawVarint32();
       if (size > 0 && size <= remaining()) {
         // TODO(nathanmittler): Is there a way to avoid this copy?
-        byte[] bytes = copyToArray(pos, pos + size);
+        // The same as readBytes' logic
+        byte[] bytes = new byte[size];
+        UnsafeUtil.copyMemory(pos, bytes, 0, size);
         String result = new String(bytes, UTF_8);
         pos += size;
         return result;
@@ -1449,7 +1509,9 @@ public abstract class CodedInputStream {
       final int size = readRawVarint32();
       if (size >= 0 && size <= remaining()) {
         // TODO(nathanmittler): Is there a way to avoid this copy?
-        byte[] bytes = copyToArray(pos, pos + size);
+        // The same as readBytes' logic
+        byte[] bytes = new byte[size];
+        UnsafeUtil.copyMemory(pos, bytes, 0, size);
         // TODO(martinrb): We could save a pass by validating while decoding.
         if (!Utf8.isValidUtf8(bytes)) {
           throw InvalidProtocolBufferException.invalidUtf8();
@@ -1545,14 +1607,17 @@ public abstract class CodedInputStream {
     public ByteString readBytes() throws IOException {
       final int size = readRawVarint32();
       if (size > 0 && size <= remaining()) {
-        ByteBuffer result;
         if (immutable && enableAliasing) {
-          result = slice(pos, pos + size);
+          final ByteBuffer result = slice(pos, pos + size);
+          pos += size;
+          return ByteString.wrap(result);
         } else {
-          result = copy(pos, pos + size);
+          // Use UnsafeUtil to copy the memory to bytes instead of using ByteBuffer ways.
+          byte[] bytes = new byte[size];
+          UnsafeUtil.copyMemory(pos, bytes, 0, size);
+          pos += size;
+          return ByteString.wrap(bytes);
         }
-        pos += size;
-        return ByteString.wrap(result);
       }
 
       if (size == 0) {
@@ -1573,18 +1638,21 @@ public abstract class CodedInputStream {
     public ByteBuffer readByteBuffer() throws IOException {
       final int size = readRawVarint32();
       if (size > 0 && size <= remaining()) {
-        ByteBuffer result;
         // "Immutable" implies that buffer is backing a ByteString.
         // Disallow slicing in this case to prevent the caller from modifying the contents
         // of the ByteString.
         if (!immutable && enableAliasing) {
-          result = slice(pos, pos + size);
+          final ByteBuffer result = slice(pos, pos + size);
+          pos += size;
+          return result;
         } else {
-          result = copy(pos, pos + size);
+          // The same as readBytes' logic
+          byte[] bytes = new byte[size];
+          UnsafeUtil.copyMemory(pos, bytes, 0, size);
+          pos += size;
+          return ByteBuffer.wrap(bytes);
         }
-        pos += size;
         // TODO(nathanmittler): Investigate making the ByteBuffer be made read-only
-        return result;
       }
 
       if (size == 0) {
@@ -1785,11 +1853,11 @@ public abstract class CodedInputStream {
     public int readRawLittleEndian32() throws IOException {
       long tempPos = pos;
 
-      if (limit - tempPos < FIXED_32_SIZE) {
+      if (limit - tempPos < FIXED32_SIZE) {
         throw InvalidProtocolBufferException.truncatedMessage();
       }
 
-      pos = tempPos + FIXED_32_SIZE;
+      pos = tempPos + FIXED32_SIZE;
       return (((UnsafeUtil.getByte(tempPos) & 0xff))
           | ((UnsafeUtil.getByte(tempPos + 1) & 0xff) << 8)
           | ((UnsafeUtil.getByte(tempPos + 2) & 0xff) << 16)
@@ -1800,11 +1868,11 @@ public abstract class CodedInputStream {
     public long readRawLittleEndian64() throws IOException {
       long tempPos = pos;
 
-      if (limit - tempPos < FIXED_64_SIZE) {
+      if (limit - tempPos < FIXED64_SIZE) {
         throw InvalidProtocolBufferException.truncatedMessage();
       }
 
-      pos = tempPos + FIXED_64_SIZE;
+      pos = tempPos + FIXED64_SIZE;
       return (((UnsafeUtil.getByte(tempPos) & 0xffL))
           | ((UnsafeUtil.getByte(tempPos + 1) & 0xffL) << 8)
           | ((UnsafeUtil.getByte(tempPos + 2) & 0xffL) << 16)
@@ -1943,27 +2011,6 @@ public abstract class CodedInputStream {
         buffer.limit(prevLimit);
       }
     }
-
-    private ByteBuffer copy(long begin, long end) throws IOException {
-      return ByteBuffer.wrap(copyToArray(begin, end));
-    }
-
-    private byte[] copyToArray(long begin, long end) throws IOException {
-      int prevPos = buffer.position();
-      int prevLimit = buffer.limit();
-      try {
-        buffer.position(bufferPos(begin));
-        buffer.limit(bufferPos(end));
-        byte[] bytes = new byte[(int) (end - begin)];
-        buffer.get(bytes);
-        return bytes;
-      } catch (IllegalArgumentException e) {
-        throw InvalidProtocolBufferException.truncatedMessage();
-      } finally {
-        buffer.position(prevPos);
-        buffer.limit(prevLimit);
-      }
-    }
   }
 
   /**
@@ -2034,7 +2081,7 @@ public abstract class CodedInputStream {
           skipRawVarint();
           return true;
         case WireFormat.WIRETYPE_FIXED64:
-          skipRawBytes(FIXED_64_SIZE);
+          skipRawBytes(FIXED64_SIZE);
           return true;
         case WireFormat.WIRETYPE_LENGTH_DELIMITED:
           skipRawBytes(readRawVarint32());
@@ -2047,7 +2094,7 @@ public abstract class CodedInputStream {
         case WireFormat.WIRETYPE_END_GROUP:
           return false;
         case WireFormat.WIRETYPE_FIXED32:
-          skipRawBytes(FIXED_32_SIZE);
+          skipRawBytes(FIXED32_SIZE);
           return true;
         default:
           throw InvalidProtocolBufferException.invalidWireType();
@@ -2332,8 +2379,7 @@ public abstract class CodedInputStream {
       if (size == 0) {
         return ByteString.EMPTY;
       }
-      // Slow path:  Build a byte array first then copy it.
-      return ByteString.wrap(readRawBytesSlowPath(size));
+      return readBytesSlowPath(size);
     }
 
     @Override
@@ -2558,13 +2604,13 @@ public abstract class CodedInputStream {
     public int readRawLittleEndian32() throws IOException {
       int tempPos = pos;
 
-      if (bufferSize - tempPos < FIXED_32_SIZE) {
-        refillBuffer(FIXED_32_SIZE);
+      if (bufferSize - tempPos < FIXED32_SIZE) {
+        refillBuffer(FIXED32_SIZE);
         tempPos = pos;
       }
 
       final byte[] buffer = this.buffer;
-      pos = tempPos + FIXED_32_SIZE;
+      pos = tempPos + FIXED32_SIZE;
       return (((buffer[tempPos] & 0xff))
           | ((buffer[tempPos + 1] & 0xff) << 8)
           | ((buffer[tempPos + 2] & 0xff) << 16)
@@ -2575,13 +2621,13 @@ public abstract class CodedInputStream {
     public long readRawLittleEndian64() throws IOException {
       int tempPos = pos;
 
-      if (bufferSize - tempPos < FIXED_64_SIZE) {
-        refillBuffer(FIXED_64_SIZE);
+      if (bufferSize - tempPos < FIXED64_SIZE) {
+        refillBuffer(FIXED64_SIZE);
         tempPos = pos;
       }
 
       final byte[] buffer = this.buffer;
-      pos = tempPos + FIXED_64_SIZE;
+      pos = tempPos + FIXED64_SIZE;
       return (((buffer[tempPos] & 0xffL))
           | ((buffer[tempPos + 1] & 0xffL) << 8)
           | ((buffer[tempPos + 2] & 0xffL) << 16)
@@ -2675,7 +2721,13 @@ public abstract class CodedInputStream {
      */
     private void refillBuffer(int n) throws IOException {
       if (!tryRefillBuffer(n)) {
-        throw InvalidProtocolBufferException.truncatedMessage();
+        // We have to distinguish the exception between sizeLimitExceeded and truncatedMessage. So
+        // we just throw an sizeLimitExceeded exception here if it exceeds the sizeLimit
+        if (n > sizeLimit - totalBytesRetired - pos) {
+          throw InvalidProtocolBufferException.sizeLimitExceeded();
+        } else {
+          throw InvalidProtocolBufferException.truncatedMessage();
+        }
       }
     }
 
@@ -2684,8 +2736,8 @@ public abstract class CodedInputStream {
      * buffer. Caller must ensure that the requested space is not yet available, and that the
      * requested space is less than BUFFER_SIZE.
      *
-     * @return {@code true} if the bytes could be made available; {@code false} if the end of the
-     *     stream or the current limit was reached.
+     * @return {@code true} If the bytes could be made available; {@code false} 1. Current at the
+     *     end of the stream 2. The current limit was reached 3. The total size limit was reached
      */
     private boolean tryRefillBuffer(int n) throws IOException {
       if (pos + n <= bufferSize) {
@@ -2693,6 +2745,14 @@ public abstract class CodedInputStream {
             "refillBuffer() called when " + n + " bytes were already available in buffer");
       }
 
+      // Check whether the size of total message needs to read is bigger than the size limit.
+      // We shouldn't throw an exception here as isAtEnd() function needs to get this function's
+      // return as the result.
+      if (n > sizeLimit - totalBytesRetired - pos) {
+        return false;
+      }
+
+      // Shouldn't throw the exception here either.
       if (totalBytesRetired + pos + n > currentLimit) {
         // Oops, we hit a limit.
         return false;
@@ -2712,7 +2772,16 @@ public abstract class CodedInputStream {
         pos = 0;
       }
 
-      int bytesRead = input.read(buffer, bufferSize, buffer.length - bufferSize);
+      // Here we should refill the buffer as many bytes as possible.
+      int bytesRead =
+          input.read(
+              buffer,
+              bufferSize,
+              Math.min(
+                  //  the size of allocated but unused bytes in the buffer
+                  buffer.length - bufferSize,
+                  //  do not exceed the total bytes limit
+                  sizeLimit - totalBytesRetired - bufferSize));
       if (bytesRead == 0 || bytesRead < -1 || bytesRead > buffer.length) {
         throw new IllegalStateException(
             "InputStream#read(byte[]) returned invalid result: "
@@ -2721,10 +2790,6 @@ public abstract class CodedInputStream {
       }
       if (bytesRead > 0) {
         bufferSize += bytesRead;
-        // Integer-overflow-conscious check against sizeLimit
-        if (totalBytesRetired + n - sizeLimit > 0) {
-          throw InvalidProtocolBufferException.sizeLimitExceeded();
-        }
         recomputeBufferSizeAfterLimit();
         return (bufferSize >= n) ? true : tryRefillBuffer(n);
       }
@@ -2756,6 +2821,49 @@ public abstract class CodedInputStream {
      * (bufferSize - pos) && size > 0)
      */
     private byte[] readRawBytesSlowPath(final int size) throws IOException {
+      // Attempt to read the data in one byte array when it's safe to do.
+      byte[] result = readRawBytesSlowPathOneChunk(size);
+      if (result != null) {
+        return result;
+      }
+
+      final int originalBufferPos = pos;
+      final int bufferedBytes = bufferSize - pos;
+
+      // Mark the current buffer consumed.
+      totalBytesRetired += bufferSize;
+      pos = 0;
+      bufferSize = 0;
+
+      // Determine the number of bytes we need to read from the input stream.
+      int sizeLeft = size - bufferedBytes;
+
+      // The size is very large. For security reasons we read them in small
+      // chunks.
+      List<byte[]> chunks = readRawBytesSlowPathRemainingChunks(sizeLeft);
+
+      // OK, got everything.  Now concatenate it all into one buffer.
+      final byte[] bytes = new byte[size];
+
+      // Start by copying the leftover bytes from this.buffer.
+      System.arraycopy(buffer, originalBufferPos, bytes, 0, bufferedBytes);
+
+      // And now all the chunks.
+      int tempPos = bufferedBytes;
+      for (final byte[] chunk : chunks) {
+        System.arraycopy(chunk, 0, bytes, tempPos, chunk.length);
+        tempPos += chunk.length;
+      }
+
+      // Done.
+      return bytes;
+    }
+
+    /**
+     * Attempts to read the data in one byte array when it's safe to do. Returns null if the size to
+     * read is too large and needs to be allocated in smaller chunks for security reasons.
+     */
+    private byte[] readRawBytesSlowPathOneChunk(final int size) throws IOException {
       if (size == 0) {
         return Internal.EMPTY_BYTE_ARRAY;
       }
@@ -2776,14 +2884,7 @@ public abstract class CodedInputStream {
         throw InvalidProtocolBufferException.truncatedMessage();
       }
 
-      final int originalBufferPos = pos;
       final int bufferedBytes = bufferSize - pos;
-
-      // Mark the current buffer consumed.
-      totalBytesRetired += bufferSize;
-      pos = 0;
-      bufferSize = 0;
-
       // Determine the number of bytes we need to read from the input stream.
       int sizeLeft = size - bufferedBytes;
       // TODO(nathanmittler): Consider using a value larger than DEFAULT_BUFFER_SIZE.
@@ -2793,7 +2894,10 @@ public abstract class CodedInputStream {
         final byte[] bytes = new byte[size];
 
         // Copy all of the buffered bytes to the result buffer.
-        System.arraycopy(buffer, originalBufferPos, bytes, 0, bufferedBytes);
+        System.arraycopy(buffer, pos, bytes, 0, bufferedBytes);
+        totalBytesRetired += bufferSize;
+        pos = 0;
+        bufferSize = 0;
 
         // Fill the remaining bytes from the input stream.
         int tempPos = bufferedBytes;
@@ -2809,6 +2913,11 @@ public abstract class CodedInputStream {
         return bytes;
       }
 
+      return null;
+    }
+
+    /** Reads the remaining data in small chunks from the input stream. */
+    private List<byte[]> readRawBytesSlowPathRemainingChunks(int sizeLeft) throws IOException {
       // The size is very large.  For security reasons, we can't allocate the
       // entire byte array yet.  The size comes directly from the input, so a
       // maliciously-crafted message could provide a bogus very large size in
@@ -2834,21 +2943,41 @@ public abstract class CodedInputStream {
         chunks.add(chunk);
       }
 
-      // OK, got everything.  Now concatenate it all into one buffer.
-      final byte[] bytes = new byte[size];
-
-      // Start by copying the leftover bytes from this.buffer.
-      System.arraycopy(buffer, originalBufferPos, bytes, 0, bufferedBytes);
+      return chunks;
+    }
 
-      // And now all the chunks.
-      int tempPos = bufferedBytes;
-      for (final byte[] chunk : chunks) {
-        System.arraycopy(chunk, 0, bytes, tempPos, chunk.length);
-        tempPos += chunk.length;
+    /**
+     * Like readBytes, but caller must have already checked the fast path: (size <= (bufferSize -
+     * pos) && size > 0 || size == 0)
+     */
+    private ByteString readBytesSlowPath(final int size) throws IOException {
+      final byte[] result = readRawBytesSlowPathOneChunk(size);
+      if (result != null) {
+        return ByteString.wrap(result);
       }
 
-      // Done.
-      return bytes;
+      final int originalBufferPos = pos;
+      final int bufferedBytes = bufferSize - pos;
+
+      // Mark the current buffer consumed.
+      totalBytesRetired += bufferSize;
+      pos = 0;
+      bufferSize = 0;
+
+      // Determine the number of bytes we need to read from the input stream.
+      int sizeLeft = size - bufferedBytes;
+
+      // The size is very large. For security reasons we read them in small
+      // chunks.
+      List<byte[]> chunks = readRawBytesSlowPathRemainingChunks(sizeLeft);
+
+      // Wrap the byte arrays into a single ByteString.
+      List<ByteString> byteStrings = new ArrayList<ByteString>(1 + chunks.size());
+      byteStrings.add(ByteString.copyFrom(buffer, originalBufferPos, bufferedBytes));
+      for (byte[] chunk : chunks) {
+        byteStrings.add(ByteString.wrap(chunk));
+      }
+      return ByteString.copyFrom(byteStrings);
     }
 
     @Override
diff --git a/java/core/src/main/java/com/google/protobuf/CodedOutputStream.java b/java/core/src/main/java/com/google/protobuf/CodedOutputStream.java
index da0e9b12..093a5f61 100644
--- a/java/core/src/main/java/com/google/protobuf/CodedOutputStream.java
+++ b/java/core/src/main/java/com/google/protobuf/CodedOutputStream.java
@@ -30,8 +30,8 @@
 
 package com.google.protobuf;
 
-import static com.google.protobuf.WireFormat.FIXED_32_SIZE;
-import static com.google.protobuf.WireFormat.FIXED_64_SIZE;
+import static com.google.protobuf.WireFormat.FIXED32_SIZE;
+import static com.google.protobuf.WireFormat.FIXED64_SIZE;
 import static com.google.protobuf.WireFormat.MAX_VARINT_SIZE;
 import static java.lang.Math.max;
 
@@ -59,13 +59,12 @@ import java.util.logging.Logger;
 public abstract class CodedOutputStream extends ByteOutput {
   private static final Logger logger = Logger.getLogger(CodedOutputStream.class.getName());
   private static final boolean HAS_UNSAFE_ARRAY_OPERATIONS = UnsafeUtil.hasUnsafeArrayOperations();
-  private static final long ARRAY_BASE_OFFSET = UnsafeUtil.getArrayBaseOffset();
 
   /**
    * @deprecated Use {@link #computeFixed32SizeNoTag(int)} instead.
    */
   @Deprecated
-  public static final int LITTLE_ENDIAN_32_SIZE = FIXED_32_SIZE;
+  public static final int LITTLE_ENDIAN_32_SIZE = FIXED32_SIZE;
 
   /**
    * The buffer size used in {@link #newInstance(OutputStream)}.
@@ -755,7 +754,7 @@ public abstract class CodedOutputStream extends ByteOutput {
    * {@code fixed32} field.
    */
   public static int computeFixed32SizeNoTag(@SuppressWarnings("unused") final int unused) {
-    return FIXED_32_SIZE;
+    return FIXED32_SIZE;
   }
 
   /**
@@ -763,7 +762,7 @@ public abstract class CodedOutputStream extends ByteOutput {
    * {@code sfixed32} field.
    */
   public static int computeSFixed32SizeNoTag(@SuppressWarnings("unused") final int unused) {
-    return FIXED_32_SIZE;
+    return FIXED32_SIZE;
   }
 
   /**
@@ -813,7 +812,7 @@ public abstract class CodedOutputStream extends ByteOutput {
    * {@code fixed64} field.
    */
   public static int computeFixed64SizeNoTag(@SuppressWarnings("unused") final long unused) {
-    return FIXED_64_SIZE;
+    return FIXED64_SIZE;
   }
 
   /**
@@ -821,7 +820,7 @@ public abstract class CodedOutputStream extends ByteOutput {
    * {@code sfixed64} field.
    */
   public static int computeSFixed64SizeNoTag(@SuppressWarnings("unused") final long unused) {
-    return FIXED_64_SIZE;
+    return FIXED64_SIZE;
   }
 
   /**
@@ -829,7 +828,7 @@ public abstract class CodedOutputStream extends ByteOutput {
    * {@code float} field, including tag.
    */
   public static int computeFloatSizeNoTag(@SuppressWarnings("unused") final float unused) {
-    return FIXED_32_SIZE;
+    return FIXED32_SIZE;
   }
 
   /**
@@ -837,7 +836,7 @@ public abstract class CodedOutputStream extends ByteOutput {
    * {@code double} field, including tag.
    */
   public static int computeDoubleSizeNoTag(@SuppressWarnings("unused") final double unused) {
-    return FIXED_64_SIZE;
+    return FIXED64_SIZE;
   }
 
   /**
@@ -1321,15 +1320,12 @@ public abstract class CodedOutputStream extends ByteOutput {
     @Override
     public final void writeUInt32NoTag(int value) throws IOException {
       if (HAS_UNSAFE_ARRAY_OPERATIONS && spaceLeft() >= MAX_VARINT_SIZE) {
-        long pos = ARRAY_BASE_OFFSET + position;
         while (true) {
           if ((value & ~0x7F) == 0) {
-            UnsafeUtil.putByte(buffer, pos++, (byte) value);
-            position++;
+            UnsafeUtil.putByte(buffer, position++, (byte) value);
             return;
           } else {
-            UnsafeUtil.putByte(buffer, pos++, (byte) ((value & 0x7F) | 0x80));
-            position++;
+            UnsafeUtil.putByte(buffer, position++, (byte) ((value & 0x7F) | 0x80));
             value >>>= 7;
           }
         }
@@ -1367,15 +1363,12 @@ public abstract class CodedOutputStream extends ByteOutput {
     @Override
     public final void writeUInt64NoTag(long value) throws IOException {
       if (HAS_UNSAFE_ARRAY_OPERATIONS && spaceLeft() >= MAX_VARINT_SIZE) {
-        long pos = ARRAY_BASE_OFFSET + position;
         while (true) {
           if ((value & ~0x7FL) == 0) {
-            UnsafeUtil.putByte(buffer, pos++, (byte) value);
-            position++;
+            UnsafeUtil.putByte(buffer, position++, (byte) value);
             return;
           } else {
-            UnsafeUtil.putByte(buffer, pos++, (byte) (((int) value & 0x7F) | 0x80));
-            position++;
+            UnsafeUtil.putByte(buffer, position++, (byte) (((int) value & 0x7F) | 0x80));
             value >>>= 7;
           }
         }
@@ -1854,7 +1847,7 @@ public abstract class CodedOutputStream extends ByteOutput {
     }
 
     static boolean isSupported() {
-      return UnsafeUtil.hasUnsafeByteBufferOperations() && UnsafeUtil.hasUnsafeCopyMemory();
+      return UnsafeUtil.hasUnsafeByteBufferOperations();
     }
 
     @Override
@@ -2030,7 +2023,7 @@ public abstract class CodedOutputStream extends ByteOutput {
     @Override
     public void writeFixed32NoTag(int value) throws IOException {
       buffer.putInt(bufferPos(position), value);
-      position += FIXED_32_SIZE;
+      position += FIXED32_SIZE;
     }
 
     @Override
@@ -2064,7 +2057,7 @@ public abstract class CodedOutputStream extends ByteOutput {
     @Override
     public void writeFixed64NoTag(long value) throws IOException {
       buffer.putLong(bufferPos(position), value);
-      position += FIXED_64_SIZE;
+      position += FIXED64_SIZE;
     }
 
     @Override
@@ -2081,8 +2074,7 @@ public abstract class CodedOutputStream extends ByteOutput {
             String.format("Pos: %d, limit: %d, len: %d", position, limit, length));
       }
 
-      UnsafeUtil.copyMemory(
-          value, UnsafeUtil.getArrayBaseOffset() + offset, null, position, length);
+      UnsafeUtil.copyMemory(value, offset, position, length);
       position += length;
     }
 
@@ -2249,19 +2241,17 @@ public abstract class CodedOutputStream extends ByteOutput {
      */
     final void bufferUInt32NoTag(int value) {
       if (HAS_UNSAFE_ARRAY_OPERATIONS) {
-        final long originalPos = ARRAY_BASE_OFFSET + position;
-        long pos = originalPos;
+        final long originalPos = position;
         while (true) {
           if ((value & ~0x7F) == 0) {
-            UnsafeUtil.putByte(buffer, pos++, (byte) value);
+            UnsafeUtil.putByte(buffer, position++, (byte) value);
             break;
           } else {
-            UnsafeUtil.putByte(buffer, pos++, (byte) ((value & 0x7F) | 0x80));
+            UnsafeUtil.putByte(buffer, position++, (byte) ((value & 0x7F) | 0x80));
             value >>>= 7;
           }
         }
-        int delta = (int) (pos - originalPos);
-        position += delta;
+        int delta = (int) (position - originalPos);
         totalBytesWritten += delta;
       } else {
         while (true) {
@@ -2284,19 +2274,17 @@ public abstract class CodedOutputStream extends ByteOutput {
      */
     final void bufferUInt64NoTag(long value) {
       if (HAS_UNSAFE_ARRAY_OPERATIONS) {
-        final long originalPos = ARRAY_BASE_OFFSET + position;
-        long pos = originalPos;
+        final long originalPos = position;
         while (true) {
           if ((value & ~0x7FL) == 0) {
-            UnsafeUtil.putByte(buffer, pos++, (byte) value);
+            UnsafeUtil.putByte(buffer, position++, (byte) value);
             break;
           } else {
-            UnsafeUtil.putByte(buffer, pos++, (byte) (((int) value & 0x7F) | 0x80));
+            UnsafeUtil.putByte(buffer, position++, (byte) (((int) value & 0x7F) | 0x80));
             value >>>= 7;
           }
         }
-        int delta = (int) (pos - originalPos);
-        position += delta;
+        int delta = (int) (position - originalPos);
         totalBytesWritten += delta;
       } else {
         while (true) {
@@ -2322,7 +2310,7 @@ public abstract class CodedOutputStream extends ByteOutput {
       buffer[position++] = (byte) ((value >> 8) & 0xFF);
       buffer[position++] = (byte) ((value >> 16) & 0xFF);
       buffer[position++] = (byte) ((value >> 24) & 0xFF);
-      totalBytesWritten += FIXED_32_SIZE;
+      totalBytesWritten += FIXED32_SIZE;
     }
 
     /**
@@ -2338,7 +2326,7 @@ public abstract class CodedOutputStream extends ByteOutput {
       buffer[position++] = (byte) ((int) (value >> 40) & 0xFF);
       buffer[position++] = (byte) ((int) (value >> 48) & 0xFF);
       buffer[position++] = (byte) ((int) (value >> 56) & 0xFF);
-      totalBytesWritten += FIXED_64_SIZE;
+      totalBytesWritten += FIXED64_SIZE;
     }
   }
 
@@ -2379,7 +2367,7 @@ public abstract class CodedOutputStream extends ByteOutput {
 
     @Override
     public void writeFixed32(final int fieldNumber, final int value) throws IOException {
-      flushIfNotAvailable(MAX_VARINT_SIZE + FIXED_32_SIZE);
+      flushIfNotAvailable(MAX_VARINT_SIZE + FIXED32_SIZE);
       bufferTag(fieldNumber, WireFormat.WIRETYPE_FIXED32);
       bufferFixed32NoTag(value);
     }
@@ -2393,7 +2381,7 @@ public abstract class CodedOutputStream extends ByteOutput {
 
     @Override
     public void writeFixed64(final int fieldNumber, final long value) throws IOException {
-      flushIfNotAvailable(MAX_VARINT_SIZE + FIXED_64_SIZE);
+      flushIfNotAvailable(MAX_VARINT_SIZE + FIXED64_SIZE);
       bufferTag(fieldNumber, WireFormat.WIRETYPE_FIXED64);
       bufferFixed64NoTag(value);
     }
@@ -2519,7 +2507,7 @@ public abstract class CodedOutputStream extends ByteOutput {
 
     @Override
     public void writeFixed32NoTag(final int value) throws IOException {
-      flushIfNotAvailable(FIXED_32_SIZE);
+      flushIfNotAvailable(FIXED32_SIZE);
       bufferFixed32NoTag(value);
     }
 
@@ -2531,7 +2519,7 @@ public abstract class CodedOutputStream extends ByteOutput {
 
     @Override
     public void writeFixed64NoTag(final long value) throws IOException {
-      flushIfNotAvailable(FIXED_64_SIZE);
+      flushIfNotAvailable(FIXED64_SIZE);
       bufferFixed64NoTag(value);
     }
 
@@ -2682,7 +2670,7 @@ public abstract class CodedOutputStream extends ByteOutput {
 
     @Override
     public void writeFixed32(final int fieldNumber, final int value) throws IOException {
-      flushIfNotAvailable(MAX_VARINT_SIZE + FIXED_32_SIZE);
+      flushIfNotAvailable(MAX_VARINT_SIZE + FIXED32_SIZE);
       bufferTag(fieldNumber, WireFormat.WIRETYPE_FIXED32);
       bufferFixed32NoTag(value);
     }
@@ -2696,7 +2684,7 @@ public abstract class CodedOutputStream extends ByteOutput {
 
     @Override
     public void writeFixed64(final int fieldNumber, final long value) throws IOException {
-      flushIfNotAvailable(MAX_VARINT_SIZE + FIXED_64_SIZE);
+      flushIfNotAvailable(MAX_VARINT_SIZE + FIXED64_SIZE);
       bufferTag(fieldNumber, WireFormat.WIRETYPE_FIXED64);
       bufferFixed64NoTag(value);
     }
@@ -2822,7 +2810,7 @@ public abstract class CodedOutputStream extends ByteOutput {
 
     @Override
     public void writeFixed32NoTag(final int value) throws IOException {
-      flushIfNotAvailable(FIXED_32_SIZE);
+      flushIfNotAvailable(FIXED32_SIZE);
       bufferFixed32NoTag(value);
     }
 
@@ -2834,7 +2822,7 @@ public abstract class CodedOutputStream extends ByteOutput {
 
     @Override
     public void writeFixed64NoTag(final long value) throws IOException {
-      flushIfNotAvailable(FIXED_64_SIZE);
+      flushIfNotAvailable(FIXED64_SIZE);
       bufferFixed64NoTag(value);
     }
 
diff --git a/java/core/src/main/java/com/google/protobuf/DiscardUnknownFieldsParser.java b/java/core/src/main/java/com/google/protobuf/DiscardUnknownFieldsParser.java
new file mode 100644
index 00000000..7ae94349
--- /dev/null
+++ b/java/core/src/main/java/com/google/protobuf/DiscardUnknownFieldsParser.java
@@ -0,0 +1,71 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+/**
+ * Parsers to discard unknown fields during parsing.
+ */
+public final class DiscardUnknownFieldsParser {
+
+  /**
+   * Warps a given {@link Parser} into a new {@link Parser} that discards unknown fields during
+   * parsing.
+   *
+   * <p>Usage example:
+   * <pre>{@code
+     * private final static Parser<Foo> FOO_PARSER = DiscardUnknownFieldsParser.wrap(Foo.parser());
+     * Foo parseFooDiscardUnknown(ByteBuffer input) throws IOException {
+     *   return FOO_PARSER.parseFrom(input);
+     * }
+   * }</pre>
+   *
+   * <p>Like all other implementations of {@code Parser}, this parser is stateless and thread-safe.
+   *
+   * @param parser The delegated parser that parses messages.
+   * @return a {@link Parser} that will discard unknown fields during parsing.
+   */
+  public static final <T extends Message> Parser<T> wrap(final Parser<T> parser) {
+    return new AbstractParser<T>() {
+      @Override
+      public T parsePartialFrom(CodedInputStream input, ExtensionRegistryLite extensionRegistry)
+          throws InvalidProtocolBufferException {
+        try {
+          input.discardUnknownFields();
+          return parser.parsePartialFrom(input, extensionRegistry);
+        } finally {
+          input.unsetDiscardUnknownFields();
+        }
+      }
+    };
+  }
+
+  private DiscardUnknownFieldsParser() {}
+}
diff --git a/java/core/src/main/java/com/google/protobuf/DynamicMessage.java b/java/core/src/main/java/com/google/protobuf/DynamicMessage.java
index 2631db74..ba532021 100644
--- a/java/core/src/main/java/com/google/protobuf/DynamicMessage.java
+++ b/java/core/src/main/java/com/google/protobuf/DynamicMessage.java
@@ -590,9 +590,8 @@ public final class DynamicMessage extends AbstractMessage {
 
     @Override
     public Builder setUnknownFields(UnknownFieldSet unknownFields) {
-      if (getDescriptorForType().getFile().getSyntax()
-          == Descriptors.FileDescriptor.Syntax.PROTO3) {
-        // Proto3 discards unknown fields.
+      if (getDescriptorForType().getFile().getSyntax() == Descriptors.FileDescriptor.Syntax.PROTO3
+          && CodedInputStream.getProto3DiscardUnknownFieldsDefault()) {
         return this;
       }
       this.unknownFields = unknownFields;
@@ -601,9 +600,8 @@ public final class DynamicMessage extends AbstractMessage {
 
     @Override
     public Builder mergeUnknownFields(UnknownFieldSet unknownFields) {
-      if (getDescriptorForType().getFile().getSyntax()
-          == Descriptors.FileDescriptor.Syntax.PROTO3) {
-        // Proto3 discards unknown fields.
+      if (getDescriptorForType().getFile().getSyntax() == Descriptors.FileDescriptor.Syntax.PROTO3
+          && CodedInputStream.getProto3DiscardUnknownFieldsDefault()) {
         return this;
       }
       this.unknownFields =
diff --git a/java/core/src/main/java/com/google/protobuf/Extension.java b/java/core/src/main/java/com/google/protobuf/Extension.java
index 08ec5b45..5df12e64 100644
--- a/java/core/src/main/java/com/google/protobuf/Extension.java
+++ b/java/core/src/main/java/com/google/protobuf/Extension.java
@@ -58,10 +58,7 @@ public abstract class Extension<ContainingType extends MessageLite, Type>
     PROTO1,
   }
 
-  protected ExtensionType getExtensionType() {
-    // TODO(liujisi): make this abstract after we fix proto1.
-    return ExtensionType.IMMUTABLE;
-  }
+  protected abstract ExtensionType getExtensionType();
 
   /**
    * Type of a message extension.
@@ -70,7 +67,7 @@ public abstract class Extension<ContainingType extends MessageLite, Type>
     PROTO1,
     PROTO2,
   }
-  
+
   /**
    * If the extension is a message extension (i.e., getLiteType() == MESSAGE),
    * returns the type of the message, otherwise undefined.
diff --git a/java/core/src/main/java/com/google/protobuf/ExtensionRegistryFactory.java b/java/core/src/main/java/com/google/protobuf/ExtensionRegistryFactory.java
index 23174e24..89f7ab9b 100644
--- a/java/core/src/main/java/com/google/protobuf/ExtensionRegistryFactory.java
+++ b/java/core/src/main/java/com/google/protobuf/ExtensionRegistryFactory.java
@@ -34,7 +34,7 @@ import static com.google.protobuf.ExtensionRegistryLite.EMPTY_REGISTRY_LITE;
 
 /**
  * A factory object to create instances of {@link ExtensionRegistryLite}.
- * 
+ *
  * <p>
  * This factory detects (via reflection) if the full (non-Lite) protocol buffer libraries
  * are available, and if so, the instances returned are actually {@link ExtensionRegistry}.
@@ -82,6 +82,7 @@ final class ExtensionRegistryFactory {
     return EMPTY_REGISTRY_LITE;
   }
 
+
   static boolean isFullRegistry(ExtensionRegistryLite registry) {
     return EXTENSION_REGISTRY_CLASS != null
         && EXTENSION_REGISTRY_CLASS.isAssignableFrom(registry.getClass());
@@ -90,6 +91,6 @@ final class ExtensionRegistryFactory {
   private static final ExtensionRegistryLite invokeSubclassFactory(String methodName)
       throws Exception {
     return (ExtensionRegistryLite) EXTENSION_REGISTRY_CLASS
-        .getMethod(methodName).invoke(null);
+        .getDeclaredMethod(methodName).invoke(null);
   }
 }
diff --git a/java/core/src/main/java/com/google/protobuf/GeneratedMessageLite.java b/java/core/src/main/java/com/google/protobuf/GeneratedMessageLite.java
index cf3486e1..7116ae1c 100644
--- a/java/core/src/main/java/com/google/protobuf/GeneratedMessageLite.java
+++ b/java/core/src/main/java/com/google/protobuf/GeneratedMessageLite.java
@@ -107,11 +107,12 @@ public abstract class GeneratedMessageLite<
   @SuppressWarnings("unchecked") // Guaranteed by runtime
   @Override
   public int hashCode() {
-    if (memoizedHashCode == 0) {
-      HashCodeVisitor visitor = new HashCodeVisitor();
-      visit(visitor, (MessageType) this);
-      memoizedHashCode = visitor.hashCode;
+    if (memoizedHashCode != 0) {
+      return memoizedHashCode;
     }
+    HashCodeVisitor visitor = new HashCodeVisitor();
+    visit(visitor, (MessageType) this);
+    memoizedHashCode = visitor.hashCode;
     return memoizedHashCode;
   }
 
@@ -331,7 +332,7 @@ public abstract class GeneratedMessageLite<
       if (isBuilt) {
         MessageType newInstance =
             (MessageType) instance.dynamicMethod(MethodToInvoke.NEW_MUTABLE_INSTANCE);
-        newInstance.visit(MergeFromVisitor.INSTANCE, instance);
+        mergeFromInstance(newInstance, instance);
         instance = newInstance;
         isBuilt = false;
       }
@@ -386,10 +387,14 @@ public abstract class GeneratedMessageLite<
     /** All subclasses implement this. */
     public BuilderType mergeFrom(MessageType message) {
       copyOnWrite();
-      instance.visit(MergeFromVisitor.INSTANCE, message);
+      mergeFromInstance(instance, message);
       return (BuilderType) this;
     }
 
+    private void mergeFromInstance(MessageType dest, MessageType src) {
+      dest.visit(MergeFromVisitor.INSTANCE, src);
+    }
+
     @Override
     public MessageType getDefaultInstanceForType() {
       return defaultInstance;
@@ -1713,7 +1718,6 @@ public abstract class GeneratedMessageLite<
     Object visitOneofLong(boolean minePresent, Object mine, Object other);
     Object visitOneofString(boolean minePresent, Object mine, Object other);
     Object visitOneofByteString(boolean minePresent, Object mine, Object other);
-    Object visitOneofLazyMessage(boolean minePresent, Object mine, Object other);
     Object visitOneofMessage(boolean minePresent, Object mine, Object other);
     void visitOneofNotSet(boolean minePresent);
 
@@ -1721,7 +1725,6 @@ public abstract class GeneratedMessageLite<
      * Message fields use null sentinals.
      */
     <T extends MessageLite> T visitMessage(T mine, T other);
-    LazyFieldLite visitLazyMessage(LazyFieldLite mine, LazyFieldLite other);
 
     <T> ProtobufList<T> visitList(ProtobufList<T> mine, ProtobufList<T> other);
     BooleanList visitBooleanList(BooleanList mine, BooleanList other);
@@ -1865,14 +1868,6 @@ public abstract class GeneratedMessageLite<
     }
 
     @Override
-    public Object visitOneofLazyMessage(boolean minePresent, Object mine, Object other) {
-      if (minePresent && mine.equals(other)) {
-        return mine;
-      }
-      throw NOT_EQUALS;
-    }
-
-    @Override
     public Object visitOneofMessage(boolean minePresent, Object mine, Object other) {
       if (minePresent && ((GeneratedMessageLite<?, ?>) mine).equals(this, (MessageLite) other)) {
         return mine;
@@ -1903,21 +1898,6 @@ public abstract class GeneratedMessageLite<
     }
 
     @Override
-    public LazyFieldLite visitLazyMessage(
-        LazyFieldLite mine, LazyFieldLite other) {
-      if (mine == null && other == null) {
-        return null;
-      }
-      if (mine == null || other == null) {
-        throw NOT_EQUALS;
-      }
-      if (mine.equals(other)) {
-        return mine;
-      }
-      throw NOT_EQUALS;
-    }
-
-    @Override
     public <T> ProtobufList<T> visitList(ProtobufList<T> mine, ProtobufList<T> other) {
       if (!mine.equals(other)) {
         throw NOT_EQUALS;
@@ -2094,12 +2074,6 @@ public abstract class GeneratedMessageLite<
     }
 
     @Override
-    public Object visitOneofLazyMessage(boolean minePresent, Object mine, Object other) {
-      hashCode = (53 * hashCode) + mine.hashCode();
-      return mine;
-    }
-
-    @Override
     public Object visitOneofMessage(boolean minePresent, Object mine, Object other) {
       return visitMessage((MessageLite) mine, (MessageLite) other);
     }
@@ -2128,18 +2102,6 @@ public abstract class GeneratedMessageLite<
     }
 
     @Override
-    public LazyFieldLite visitLazyMessage(LazyFieldLite mine, LazyFieldLite other) {
-      final int protoHash;
-      if (mine != null) {
-        protoHash = mine.hashCode();
-      } else {
-        protoHash = 37;
-      }
-      hashCode = (53 * hashCode) + protoHash;
-      return mine;
-    }
-
-    @Override
     public <T> ProtobufList<T> visitList(ProtobufList<T> mine, ProtobufList<T> other) {
       hashCode = (53 * hashCode) + mine.hashCode();
       return mine;
@@ -2282,13 +2244,6 @@ public abstract class GeneratedMessageLite<
     }
 
     @Override
-    public Object visitOneofLazyMessage(boolean minePresent, Object mine, Object other) {
-      LazyFieldLite lazy = minePresent ? (LazyFieldLite) mine : new LazyFieldLite();
-      lazy.merge((LazyFieldLite) other);
-      return lazy;
-    }
-
-    @Override
     public Object visitOneofMessage(boolean minePresent, Object mine, Object other) {
       if (minePresent) {
         return visitMessage((MessageLite) mine, (MessageLite) other);
@@ -2312,17 +2267,6 @@ public abstract class GeneratedMessageLite<
     }
 
     @Override
-    public LazyFieldLite visitLazyMessage(LazyFieldLite mine, LazyFieldLite other) {
-      if (other != null) {
-        if (mine == null) {
-          mine = new LazyFieldLite();
-        }
-        mine.merge(other);
-      }
-      return mine;
-    }
-
-    @Override
     public <T> ProtobufList<T> visitList(ProtobufList<T> mine, ProtobufList<T> other) {
       int size = mine.size();
       int otherSize = other.size();
diff --git a/java/core/src/main/java/com/google/protobuf/GeneratedMessageV3.java b/java/core/src/main/java/com/google/protobuf/GeneratedMessageV3.java
index b949cd17..592869a1 100644
--- a/java/core/src/main/java/com/google/protobuf/GeneratedMessageV3.java
+++ b/java/core/src/main/java/com/google/protobuf/GeneratedMessageV3.java
@@ -30,6 +30,8 @@
 
 package com.google.protobuf;
 
+import static com.google.protobuf.Internal.checkNotNull;
+
 import com.google.protobuf.Descriptors.Descriptor;
 import com.google.protobuf.Descriptors.EnumDescriptor;
 import com.google.protobuf.Descriptors.EnumValueDescriptor;
@@ -47,7 +49,6 @@ import com.google.protobuf.Descriptors.OneofDescriptor;
 // to be able to use GeneratedMessage.GeneratedExtension. The GeneratedExtension definition in
 // this file is also excluded from opensource to avoid conflict.
 import com.google.protobuf.GeneratedMessage.GeneratedExtension;
-
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.ObjectStreamException;
@@ -277,13 +278,30 @@ public abstract class GeneratedMessageV3 extends AbstractMessage
 
   /**
    * Called by subclasses to parse an unknown field.
+   *
    * @return {@code true} unless the tag is an end-group tag.
    */
   protected boolean parseUnknownField(
       CodedInputStream input,
       UnknownFieldSet.Builder unknownFields,
       ExtensionRegistryLite extensionRegistry,
-      int tag) throws IOException {
+      int tag)
+      throws IOException {
+    if (input.shouldDiscardUnknownFields()) {
+      return input.skipField(tag);
+    }
+    return unknownFields.mergeFieldFrom(tag, input);
+  }
+
+  protected boolean parseUnknownFieldProto3(
+      CodedInputStream input,
+      UnknownFieldSet.Builder unknownFields,
+      ExtensionRegistryLite extensionRegistry,
+      int tag)
+      throws IOException {
+    if (input.shouldDiscardUnknownFieldsProto3()) {
+      return input.skipField(tag);
+    }
     return unknownFields.mergeFieldFrom(tag, input);
   }
 
@@ -619,15 +637,22 @@ public abstract class GeneratedMessageV3 extends AbstractMessage
       return (BuilderType) this;
     }
 
+    protected BuilderType setUnknownFieldsProto3(final UnknownFieldSet unknownFields) {
+      if (CodedInputStream.getProto3DiscardUnknownFieldsDefault()) {
+        return (BuilderType) this;
+      }
+      this.unknownFields = unknownFields;
+      onChanged();
+      return (BuilderType) this;
+    }
+
     @Override
     public BuilderType mergeUnknownFields(
         final UnknownFieldSet unknownFields) {
-      this.unknownFields =
+      return setUnknownFields(
         UnknownFieldSet.newBuilder(this.unknownFields)
                        .mergeFrom(unknownFields)
-                       .build();
-      onChanged();
-      return (BuilderType) this;
+                       .build());
     }
 
     @Override
@@ -666,18 +691,6 @@ public abstract class GeneratedMessageV3 extends AbstractMessage
     }
 
     /**
-     * Called by subclasses to parse an unknown field.
-     * @return {@code true} unless the tag is an end-group tag.
-     */
-    protected boolean parseUnknownField(
-        final CodedInputStream input,
-        final UnknownFieldSet.Builder unknownFields,
-        final ExtensionRegistryLite extensionRegistry,
-        final int tag) throws IOException {
-      return unknownFields.mergeFieldFrom(tag, input);
-    }
-
-    /**
      * Implementation of {@link BuilderParent} for giving to our children. This
      * small inner class makes it so we don't publicly expose the BuilderParent
      * methods.
@@ -987,8 +1000,23 @@ public abstract class GeneratedMessageV3 extends AbstractMessage
         ExtensionRegistryLite extensionRegistry,
         int tag) throws IOException {
       return MessageReflection.mergeFieldFrom(
-          input, unknownFields, extensionRegistry, getDescriptorForType(),
-          new MessageReflection.ExtensionAdapter(extensions), tag);
+          input, input.shouldDiscardUnknownFields() ? null : unknownFields, extensionRegistry,
+          getDescriptorForType(), new MessageReflection.ExtensionAdapter(extensions), tag);
+    }
+
+    @Override
+    protected boolean parseUnknownFieldProto3(
+        CodedInputStream input,
+        UnknownFieldSet.Builder unknownFields,
+        ExtensionRegistryLite extensionRegistry,
+        int tag) throws IOException {
+      return MessageReflection.mergeFieldFrom(
+          input,
+          input.shouldDiscardUnknownFieldsProto3() ? null : unknownFields,
+          extensionRegistry,
+          getDescriptorForType(),
+          new MessageReflection.ExtensionAdapter(extensions),
+          tag);
     }
 
 
@@ -1458,21 +1486,6 @@ public abstract class GeneratedMessageV3 extends AbstractMessage
       return super.isInitialized() && extensionsAreInitialized();
     }
 
-    /**
-     * Called by subclasses to parse an unknown field or an extension.
-     * @return {@code true} unless the tag is an end-group tag.
-     */
-    @Override
-    protected boolean parseUnknownField(
-        final CodedInputStream input,
-        final UnknownFieldSet.Builder unknownFields,
-        final ExtensionRegistryLite extensionRegistry,
-        final int tag) throws IOException {
-      return MessageReflection.mergeFieldFrom(
-          input, unknownFields, extensionRegistry, getDescriptorForType(),
-          new MessageReflection.BuilderAdapter(this), tag);
-    }
-
     // ---------------------------------------------------------------
     // Reflection
 
@@ -2277,7 +2290,7 @@ public abstract class GeneratedMessageV3 extends AbstractMessage
       public Object getRepeatedRaw(Builder builder, int index) {
         return getRepeated(builder, index);
       }
-      
+
       @Override
       public void setRepeated(Builder builder, int index, Object value) {
         getMutableMapField(builder).getMutableList().set(index, coerceType((Message) value));
@@ -2678,7 +2691,7 @@ public abstract class GeneratedMessageV3 extends AbstractMessage
 
     return (Extension<MessageType, T>) extension;
   }
-  
+
   protected static int computeStringSize(final int fieldNumber, final Object value) {
     if (value instanceof String) {
       return CodedOutputStream.computeStringSize(fieldNumber, (String) value);
@@ -2686,7 +2699,7 @@ public abstract class GeneratedMessageV3 extends AbstractMessage
       return CodedOutputStream.computeBytesSize(fieldNumber, (ByteString) value);
     }
   }
-  
+
   protected static int computeStringSizeNoTag(final Object value) {
     if (value instanceof String) {
       return CodedOutputStream.computeStringSizeNoTag((String) value);
@@ -2694,7 +2707,7 @@ public abstract class GeneratedMessageV3 extends AbstractMessage
       return CodedOutputStream.computeBytesSizeNoTag((ByteString) value);
     }
   }
-  
+
   protected static void writeString(
       CodedOutputStream output, final int fieldNumber, final Object value) throws IOException {
     if (value instanceof String) {
@@ -2703,7 +2716,7 @@ public abstract class GeneratedMessageV3 extends AbstractMessage
       output.writeBytes(fieldNumber, (ByteString) value);
     }
   }
-  
+
   protected static void writeStringNoTag(
       CodedOutputStream output, final Object value) throws IOException {
     if (value instanceof String) {
diff --git a/java/core/src/main/java/com/google/protobuf/Internal.java b/java/core/src/main/java/com/google/protobuf/Internal.java
index 36bdece3..848cad03 100644
--- a/java/core/src/main/java/com/google/protobuf/Internal.java
+++ b/java/core/src/main/java/com/google/protobuf/Internal.java
@@ -414,9 +414,8 @@ public final class Internal {
     }
   }
 
-  /**
-   * An empty byte array constant used in generated code.
-   */
+
+  /** An empty byte array constant used in generated code. */
   public static final byte[] EMPTY_BYTE_ARRAY = new byte[0];
 
   /**
diff --git a/java/core/src/main/java/com/google/protobuf/InvalidProtocolBufferException.java b/java/core/src/main/java/com/google/protobuf/InvalidProtocolBufferException.java
index 55e33d21..510c6aac 100644
--- a/java/core/src/main/java/com/google/protobuf/InvalidProtocolBufferException.java
+++ b/java/core/src/main/java/com/google/protobuf/InvalidProtocolBufferException.java
@@ -50,6 +50,10 @@ public class InvalidProtocolBufferException extends IOException {
     super(e.getMessage(), e);
   }
 
+  public InvalidProtocolBufferException(final String description, IOException e) {
+    super(description, e);
+  }
+
   /**
    * Attaches an unfinished message to the exception to support best-effort
    * parsing in {@code Parser} interface.
diff --git a/java/core/src/main/java/com/google/protobuf/MessageReflection.java b/java/core/src/main/java/com/google/protobuf/MessageReflection.java
index 3d73efb3..69ad7ddf 100644
--- a/java/core/src/main/java/com/google/protobuf/MessageReflection.java
+++ b/java/core/src/main/java/com/google/protobuf/MessageReflection.java
@@ -31,7 +31,6 @@
 package com.google.protobuf;
 
 import com.google.protobuf.Descriptors.FieldDescriptor;
-
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
@@ -714,12 +713,14 @@ class MessageReflection {
   }
 
   /**
-   * Parses a single field into MergeTarget. The target can be Message.Builder,
-   * FieldSet or MutableMessage.
+   * Parses a single field into MergeTarget. The target can be Message.Builder, FieldSet or
+   * MutableMessage.
    *
-   * Package-private because it is used by GeneratedMessage.ExtendableMessage.
+   * <p>Package-private because it is used by GeneratedMessage.ExtendableMessage.
    *
    * @param tag The tag, which should have already been read.
+   * @param unknownFields If not null, unknown fields will be merged to this {@link
+   *     UnknownFieldSet}, otherwise unknown fields will be discarded.
    * @return {@code true} unless the tag is an end-group tag.
    */
   static boolean mergeFieldFrom(
@@ -728,7 +729,8 @@ class MessageReflection {
       ExtensionRegistryLite extensionRegistry,
       Descriptors.Descriptor type,
       MergeTarget target,
-      int tag) throws IOException {
+      int tag)
+      throws IOException {
     if (type.getOptions().getMessageSetWireFormat() &&
         tag == WireFormat.MESSAGE_SET_ITEM_TAG) {
       mergeMessageSetExtensionFromCodedStream(
@@ -792,7 +794,11 @@ class MessageReflection {
     }
 
     if (unknown) {  // Unknown field or wrong wire type.  Skip.
-      return unknownFields.mergeFieldFrom(tag, input);
+      if (unknownFields != null) {
+        return unknownFields.mergeFieldFrom(tag, input);
+      } else {
+        return input.skipField(tag);
+      }
     }
 
     if (packed) {
@@ -844,7 +850,9 @@ class MessageReflection {
             // If the number isn't recognized as a valid value for this enum,
             // drop it.
             if (value == null) {
-              unknownFields.mergeVarintField(fieldNumber, rawValue);
+              if (unknownFields != null) {
+                unknownFields.mergeVarintField(fieldNumber, rawValue);
+              }
               return true;
             }
           }
@@ -947,7 +955,7 @@ class MessageReflection {
         mergeMessageSetExtensionFromBytes(
             rawBytes, extension, extensionRegistry, target);
       } else { // We don't know how to parse this. Ignore it.
-        if (rawBytes != null) {
+        if (rawBytes != null && unknownFields != null) {
           unknownFields.mergeField(typeId, UnknownFieldSet.Field.newBuilder()
               .addLengthDelimited(rawBytes).build());
         }
diff --git a/java/core/src/main/java/com/google/protobuf/TextFormat.java b/java/core/src/main/java/com/google/protobuf/TextFormat.java
index 53dead80..64094d09 100644
--- a/java/core/src/main/java/com/google/protobuf/TextFormat.java
+++ b/java/core/src/main/java/com/google/protobuf/TextFormat.java
@@ -34,7 +34,6 @@ import com.google.protobuf.Descriptors.Descriptor;
 import com.google.protobuf.Descriptors.EnumDescriptor;
 import com.google.protobuf.Descriptors.EnumValueDescriptor;
 import com.google.protobuf.Descriptors.FieldDescriptor;
-
 import java.io.IOException;
 import java.math.BigInteger;
 import java.nio.CharBuffer;
@@ -56,14 +55,7 @@ import java.util.regex.Pattern;
 public final class TextFormat {
   private TextFormat() {}
 
-  private static final Logger logger =
-      Logger.getLogger(TextFormat.class.getName());
-
-  private static final Printer DEFAULT_PRINTER = new Printer();
-  private static final Printer SINGLE_LINE_PRINTER =
-      (new Printer()).setSingleLineMode(true);
-  private static final Printer UNICODE_PRINTER =
-      (new Printer()).setEscapeNonAscii(false);
+  private static final Logger logger = Logger.getLogger(TextFormat.class.getName());
 
   /**
    * Outputs a textual representation of the Protocol Message supplied into
@@ -73,14 +65,14 @@ public final class TextFormat {
   public static void print(
       final MessageOrBuilder message, final Appendable output)
       throws IOException {
-    DEFAULT_PRINTER.print(message, new TextGenerator(output));
+    Printer.DEFAULT.print(message, multiLineOutput(output));
   }
 
   /** Outputs a textual representation of {@code fields} to {@code output}. */
   public static void print(final UnknownFieldSet fields,
                            final Appendable output)
                            throws IOException {
-    DEFAULT_PRINTER.printUnknownFields(fields, new TextGenerator(output));
+    Printer.DEFAULT.printUnknownFields(fields, multiLineOutput(output));
   }
 
   /**
@@ -90,7 +82,7 @@ public final class TextFormat {
   public static void printUnicode(
       final MessageOrBuilder message, final Appendable output)
       throws IOException {
-    UNICODE_PRINTER.print(message, new TextGenerator(output));
+    Printer.UNICODE.print(message, multiLineOutput(output));
   }
 
   /**
@@ -100,7 +92,7 @@ public final class TextFormat {
   public static void printUnicode(final UnknownFieldSet fields,
                                   final Appendable output)
                                   throws IOException {
-    UNICODE_PRINTER.printUnknownFields(fields, new TextGenerator(output));
+    Printer.UNICODE.printUnknownFields(fields, multiLineOutput(output));
   }
 
   /**
@@ -109,10 +101,9 @@ public final class TextFormat {
    */
   public static String shortDebugString(final MessageOrBuilder message) {
     try {
-      final StringBuilder sb = new StringBuilder();
-      SINGLE_LINE_PRINTER.print(message, new TextGenerator(sb));
-      // Single line mode currently might have an extra space at the end.
-      return sb.toString().trim();
+      final StringBuilder text = new StringBuilder();
+      Printer.DEFAULT.print(message, singleLineOutput(text));
+      return text.toString();
     } catch (IOException e) {
       throw new IllegalStateException(e);
     }
@@ -125,11 +116,11 @@ public final class TextFormat {
   public static String shortDebugString(final FieldDescriptor field,
                                         final Object value) {
     try {
-      final StringBuilder sb = new StringBuilder();
-      SINGLE_LINE_PRINTER.printField(field, value, new TextGenerator(sb));
-      return sb.toString().trim();
+      final StringBuilder text = new StringBuilder();
+      Printer.DEFAULT.printField(field, value, singleLineOutput(text));
+      return text.toString();
     } catch (IOException e) {
-        throw new IllegalStateException(e);
+      throw new IllegalStateException(e);
     }
   }
 
@@ -139,10 +130,9 @@ public final class TextFormat {
    */
   public static String shortDebugString(final UnknownFieldSet fields) {
     try {
-      final StringBuilder sb = new StringBuilder();
-      SINGLE_LINE_PRINTER.printUnknownFields(fields, new TextGenerator(sb));
-      // Single line mode currently might have an extra space at the end.
-      return sb.toString().trim();
+      final StringBuilder text = new StringBuilder();
+      Printer.DEFAULT.printUnknownFields(fields, singleLineOutput(text));
+      return text.toString();
     } catch (IOException e) {
       throw new IllegalStateException(e);
     }
@@ -183,7 +173,7 @@ public final class TextFormat {
   public static String printToUnicodeString(final MessageOrBuilder message) {
     try {
       final StringBuilder text = new StringBuilder();
-      UNICODE_PRINTER.print(message, new TextGenerator(text));
+      Printer.UNICODE.print(message, multiLineOutput(text));
       return text.toString();
     } catch (IOException e) {
       throw new IllegalStateException(e);
@@ -197,7 +187,7 @@ public final class TextFormat {
   public static String printToUnicodeString(final UnknownFieldSet fields) {
     try {
       final StringBuilder text = new StringBuilder();
-      UNICODE_PRINTER.printUnknownFields(fields, new TextGenerator(text));
+      Printer.UNICODE.printUnknownFields(fields, multiLineOutput(text));
       return text.toString();
     } catch (IOException e) {
       throw new IllegalStateException(e);
@@ -208,7 +198,7 @@ public final class TextFormat {
                                 final Object value,
                                 final Appendable output)
                                 throws IOException {
-    DEFAULT_PRINTER.printField(field, value, new TextGenerator(output));
+    Printer.DEFAULT.printField(field, value, multiLineOutput(output));
   }
 
   public static String printFieldToString(final FieldDescriptor field,
@@ -223,6 +213,23 @@ public final class TextFormat {
   }
 
   /**
+   * Outputs a unicode textual representation of the value of given field value.
+   *
+   * <p>Same as {@code printFieldValue()}, except that non-ASCII characters in string type fields
+   * are not escaped in backslash+octals.
+   *
+   * @param field the descriptor of the field
+   * @param value the value of the field
+   * @param output the output to which to append the formatted value
+   * @throws ClassCastException if the value is not appropriate for the given field descriptor
+   * @throws IOException if there is an exception writing to the output
+   */
+  public static void printUnicodeFieldValue(
+      final FieldDescriptor field, final Object value, final Appendable output) throws IOException {
+    Printer.UNICODE.printFieldValue(field, value, multiLineOutput(output));
+  }
+
+  /**
    * Outputs a textual representation of the value of given field value.
    *
    * @param field the descriptor of the field
@@ -236,7 +243,7 @@ public final class TextFormat {
                                      final Object value,
                                      final Appendable output)
                                      throws IOException {
-    DEFAULT_PRINTER.printFieldValue(field, value, new TextGenerator(output));
+    Printer.DEFAULT.printFieldValue(field, value, multiLineOutput(output));
   }
 
   /**
@@ -253,7 +260,7 @@ public final class TextFormat {
                                             final Object value,
                                             final Appendable output)
                                             throws IOException {
-    printUnknownFieldValue(tag, value, new TextGenerator(output));
+    printUnknownFieldValue(tag, value, multiLineOutput(output));
   }
 
   private static void printUnknownFieldValue(final int tag,
@@ -277,7 +284,7 @@ public final class TextFormat {
         generator.print("\"");
         break;
       case WireFormat.WIRETYPE_START_GROUP:
-        DEFAULT_PRINTER.printUnknownFields((UnknownFieldSet) value, generator);
+        Printer.DEFAULT.printUnknownFields((UnknownFieldSet) value, generator);
         break;
       default:
         throw new IllegalArgumentException("Bad tag: " + tag);
@@ -286,24 +293,16 @@ public final class TextFormat {
 
   /** Helper class for converting protobufs to text. */
   private static final class Printer {
-    /** Whether to omit newlines from the output. */
-    boolean singleLineMode = false;
+    // Printer instance which escapes non-ASCII characters.
+    static final Printer DEFAULT = new Printer(true);
+    // Printer instance which emits Unicode (it still escapes newlines and quotes in strings).
+    static final Printer UNICODE = new Printer(false);
 
     /** Whether to escape non ASCII characters with backslash and octal. */
-    boolean escapeNonAscii = true;
-
-    private Printer() {}
+    private final boolean escapeNonAscii;
 
-    /** Setter of singleLineMode */
-    private Printer setSingleLineMode(boolean singleLineMode) {
-      this.singleLineMode = singleLineMode;
-      return this;
-    }
-
-    /** Setter of escapeNonAscii */
-    private Printer setEscapeNonAscii(boolean escapeNonAscii) {
+    private Printer(boolean escapeNonAscii) {
       this.escapeNonAscii = escapeNonAscii;
-      return this;
     }
 
     private void print(
@@ -355,12 +354,9 @@ public final class TextFormat {
       }
 
       if (field.getJavaType() == FieldDescriptor.JavaType.MESSAGE) {
-        if (singleLineMode) {
-          generator.print(" { ");
-        } else {
-          generator.print(" {\n");
-          generator.indent();
-        }
+        generator.print(" {");
+        generator.eol();
+        generator.indent();
       } else {
         generator.print(": ");
       }
@@ -368,19 +364,10 @@ public final class TextFormat {
       printFieldValue(field, value, generator);
 
       if (field.getJavaType() == FieldDescriptor.JavaType.MESSAGE) {
-        if (singleLineMode) {
-          generator.print("} ");
-        } else {
-          generator.outdent();
-          generator.print("}\n");
-        }
-      } else {
-        if (singleLineMode) {
-          generator.print(" ");
-        } else {
-          generator.print("\n");
-        }
+        generator.outdent();
+        generator.print("}");
       }
+      generator.eol();
     }
 
     private void printFieldValue(final FieldDescriptor field,
@@ -469,19 +456,13 @@ public final class TextFormat {
             field.getLengthDelimitedList(), generator);
         for (final UnknownFieldSet value : field.getGroupList()) {
           generator.print(entry.getKey().toString());
-          if (singleLineMode) {
-            generator.print(" { ");
-          } else {
-            generator.print(" {\n");
-            generator.indent();
-          }
+          generator.print(" {");
+          generator.eol();
+          generator.indent();
           printUnknownFields(value, generator);
-          if (singleLineMode) {
-            generator.print("} ");
-          } else {
-            generator.outdent();
-            generator.print("}\n");
-          }
+          generator.outdent();
+          generator.print("}");
+          generator.eol();
         }
       }
     }
@@ -495,7 +476,7 @@ public final class TextFormat {
         generator.print(String.valueOf(number));
         generator.print(": ");
         printUnknownFieldValue(wireType, value, generator);
-        generator.print(singleLineMode ? " " : "\n");
+        generator.eol();
       }
     }
   }
@@ -521,16 +502,29 @@ public final class TextFormat {
     }
   }
 
-  /**
+  private static TextGenerator multiLineOutput(Appendable output) {
+    return new TextGenerator(output, false);
+  }
+
+  private static TextGenerator singleLineOutput(Appendable output) {
+    return new TextGenerator(output, true);
+  }
+
+ /**
    * An inner class for writing text to the output stream.
    */
   private static final class TextGenerator {
     private final Appendable output;
     private final StringBuilder indent = new StringBuilder();
-    private boolean atStartOfLine = true;
+    private final boolean singleLineMode;
+    // While technically we are "at the start of a line" at the very beginning of the output, all
+    // we would do in response to this is emit the (zero length) indentation, so it has no effect.
+    // Setting it false here does however suppress an unwanted leading space in single-line mode.
+    private boolean atStartOfLine = false;
 
-    private TextGenerator(final Appendable output) {
+    private TextGenerator(final Appendable output, boolean singleLineMode) {
       this.output = output;
+      this.singleLineMode = singleLineMode;
     }
 
     /**
@@ -552,35 +546,31 @@ public final class TextFormat {
         throw new IllegalArgumentException(
             " Outdent() without matching Indent().");
       }
-      indent.delete(length - 2, length);
+      indent.setLength(length - 2);
     }
 
     /**
-     * Print text to the output stream.
+     * Print text to the output stream. Bare newlines are never expected to be passed to this
+     * method; to indicate the end of a line, call "eol()".
      */
     public void print(final CharSequence text) throws IOException {
-      final int size = text.length();
-      int pos = 0;
-
-      for (int i = 0; i < size; i++) {
-        if (text.charAt(i) == '\n') {
-          write(text.subSequence(pos, i + 1));
-          pos = i + 1;
-          atStartOfLine = true;
-        }
+      if (atStartOfLine) {
+        atStartOfLine = false;
+        output.append(singleLineMode ? " " : indent);
       }
-      write(text.subSequence(pos, size));
+      output.append(text);
     }
 
-    private void write(final CharSequence data) throws IOException {
-      if (data.length() == 0) {
-        return;
-      }
-      if (atStartOfLine) {
-        atStartOfLine = false;
-        output.append(indent);
+    /**
+     * Signifies reaching the "end of the current line" in the output. In single-line mode, this
+     * does not result in a newline being emitted, but ensures that a separating space is written
+     * before the next output.
+     */
+    public void eol() throws IOException {
+      if (!singleLineMode) {
+        output.append("\n");
       }
-      output.append(data);
+      atStartOfLine = true;
     }
   }
 
@@ -1469,9 +1459,15 @@ public final class TextFormat {
             extensionRegistry, name.toString());
 
         if (extension == null) {
-          unknownFields.add((tokenizer.getPreviousLine() + 1) + ":" +
-              (tokenizer.getPreviousColumn() + 1) + ":\t" +
-              type.getFullName() + ".[" + name + "]");
+          unknownFields.add(
+              (tokenizer.getPreviousLine() + 1)
+                  + ":"
+                  + (tokenizer.getPreviousColumn() + 1)
+                  + ":\t"
+                  + type.getFullName()
+                  + ".["
+                  + name
+                  + "]");
         } else {
           if (extension.descriptor.getContainingType() != type) {
             throw tokenizer.parseExceptionPreviousToken(
@@ -1506,9 +1502,14 @@ public final class TextFormat {
         }
 
         if (field == null) {
-          unknownFields.add((tokenizer.getPreviousLine() + 1) + ":" +
-              (tokenizer.getPreviousColumn() + 1) + ":\t" +
-              type.getFullName() + "." + name);
+          unknownFields.add(
+              (tokenizer.getPreviousLine() + 1)
+                  + ":"
+                  + (tokenizer.getPreviousColumn() + 1)
+                  + ":\t"
+                  + type.getFullName()
+                  + "."
+                  + name);
         }
       }
 
diff --git a/java/core/src/main/java/com/google/protobuf/UnknownFieldSet.java b/java/core/src/main/java/com/google/protobuf/UnknownFieldSet.java
index d9381135..37d64633 100644
--- a/java/core/src/main/java/com/google/protobuf/UnknownFieldSet.java
+++ b/java/core/src/main/java/com/google/protobuf/UnknownFieldSet.java
@@ -715,7 +715,7 @@ public final class UnknownFieldSet implements MessageLite {
    * @see UnknownFieldSet
    */
   public static final class Field {
-    Field() {}
+    private Field() {}
 
     /** Construct a new {@link Builder}. */
     public static Builder newBuilder() {
diff --git a/java/core/src/main/java/com/google/protobuf/UnsafeUtil.java b/java/core/src/main/java/com/google/protobuf/UnsafeUtil.java
index ca80d946..acc03a7c 100644
--- a/java/core/src/main/java/com/google/protobuf/UnsafeUtil.java
+++ b/java/core/src/main/java/com/google/protobuf/UnsafeUtil.java
@@ -47,8 +47,29 @@ final class UnsafeUtil {
   private static final boolean HAS_UNSAFE_BYTEBUFFER_OPERATIONS =
       supportsUnsafeByteBufferOperations();
   private static final boolean HAS_UNSAFE_ARRAY_OPERATIONS = supportsUnsafeArrayOperations();
-  private static final boolean HAS_UNSAFE_COPY_MEMORY = supportsUnsafeCopyMemory();
-  private static final long ARRAY_BASE_OFFSET = byteArrayBaseOffset();
+
+  private static final long BYTE_ARRAY_BASE_OFFSET = arrayBaseOffset(byte[].class);
+  // Micro-optimization: we can assume a scale of 1 and skip the multiply
+  // private static final long BYTE_ARRAY_INDEX_SCALE = 1;
+
+  private static final long BOOLEAN_ARRAY_BASE_OFFSET = arrayBaseOffset(boolean[].class);
+  private static final long BOOLEAN_ARRAY_INDEX_SCALE = arrayIndexScale(boolean[].class);
+
+  private static final long INT_ARRAY_BASE_OFFSET = arrayBaseOffset(int[].class);
+  private static final long INT_ARRAY_INDEX_SCALE = arrayIndexScale(int[].class);
+
+  private static final long LONG_ARRAY_BASE_OFFSET = arrayBaseOffset(long[].class);
+  private static final long LONG_ARRAY_INDEX_SCALE = arrayIndexScale(long[].class);
+
+  private static final long FLOAT_ARRAY_BASE_OFFSET = arrayBaseOffset(float[].class);
+  private static final long FLOAT_ARRAY_INDEX_SCALE = arrayIndexScale(float[].class);
+
+  private static final long DOUBLE_ARRAY_BASE_OFFSET = arrayBaseOffset(double[].class);
+  private static final long DOUBLE_ARRAY_INDEX_SCALE = arrayIndexScale(double[].class);
+
+  private static final long OBJECT_ARRAY_BASE_OFFSET = arrayBaseOffset(Object[].class);
+  private static final long OBJECT_ARRAY_INDEX_SCALE = arrayIndexScale(Object[].class);
+
   private static final long BUFFER_ADDRESS_OFFSET = fieldOffset(bufferAddressField());
 
   private UnsafeUtil() {}
@@ -57,10 +78,6 @@ final class UnsafeUtil {
     return HAS_UNSAFE_ARRAY_OPERATIONS;
   }
 
-  static boolean hasUnsafeCopyMemory() {
-    return HAS_UNSAFE_COPY_MEMORY;
-  }
-
   static boolean hasUnsafeByteBufferOperations() {
     return HAS_UNSAFE_BYTEBUFFER_OPERATIONS;
   }
@@ -69,8 +86,12 @@ final class UnsafeUtil {
     return MEMORY_ACCESSOR.objectFieldOffset(field);
   }
 
-  static long getArrayBaseOffset() {
-    return ARRAY_BASE_OFFSET;
+  private static int arrayBaseOffset(Class<?> clazz) {
+    return HAS_UNSAFE_ARRAY_OPERATIONS ? MEMORY_ACCESSOR.arrayBaseOffset(clazz) : -1;
+  }
+
+  private static int arrayIndexScale(Class<?> clazz) {
+    return HAS_UNSAFE_ARRAY_OPERATIONS ? MEMORY_ACCESSOR.arrayIndexScale(clazz) : -1;
   }
 
   static byte getByte(Object target, long offset) {
@@ -129,9 +150,82 @@ final class UnsafeUtil {
     MEMORY_ACCESSOR.putObject(target, offset, value);
   }
 
-  static void copyMemory(
-      Object src, long srcOffset, Object target, long targetOffset, long length) {
-    MEMORY_ACCESSOR.copyMemory(src, srcOffset, target, targetOffset, length);
+  static byte getByte(byte[] target, long index) {
+    return MEMORY_ACCESSOR.getByte(target, BYTE_ARRAY_BASE_OFFSET + index);
+  }
+
+  static void putByte(byte[] target, long index, byte value) {
+    MEMORY_ACCESSOR.putByte(target, BYTE_ARRAY_BASE_OFFSET + index, value);
+  }
+
+  static int getInt(int[] target, long index) {
+    return MEMORY_ACCESSOR.getInt(target, INT_ARRAY_BASE_OFFSET + (index * INT_ARRAY_INDEX_SCALE));
+  }
+
+  static void putInt(int[] target, long index, int value) {
+    MEMORY_ACCESSOR.putInt(target, INT_ARRAY_BASE_OFFSET + (index * INT_ARRAY_INDEX_SCALE), value);
+  }
+
+  static long getLong(long[] target, long index) {
+    return MEMORY_ACCESSOR.getLong(
+        target, LONG_ARRAY_BASE_OFFSET + (index * LONG_ARRAY_INDEX_SCALE));
+  }
+
+  static void putLong(long[] target, long index, long value) {
+    MEMORY_ACCESSOR.putLong(
+        target, LONG_ARRAY_BASE_OFFSET + (index * LONG_ARRAY_INDEX_SCALE), value);
+  }
+
+  static boolean getBoolean(boolean[] target, long index) {
+    return MEMORY_ACCESSOR.getBoolean(
+        target, BOOLEAN_ARRAY_BASE_OFFSET + (index * BOOLEAN_ARRAY_INDEX_SCALE));
+  }
+
+  static void putBoolean(boolean[] target, long index, boolean value) {
+    MEMORY_ACCESSOR.putBoolean(
+        target, BOOLEAN_ARRAY_BASE_OFFSET + (index * BOOLEAN_ARRAY_INDEX_SCALE), value);
+  }
+
+  static float getFloat(float[] target, long index) {
+    return MEMORY_ACCESSOR.getFloat(
+        target, FLOAT_ARRAY_BASE_OFFSET + (index * FLOAT_ARRAY_INDEX_SCALE));
+  }
+
+  static void putFloat(float[] target, long index, float value) {
+    MEMORY_ACCESSOR.putFloat(
+        target, FLOAT_ARRAY_BASE_OFFSET + (index * FLOAT_ARRAY_INDEX_SCALE), value);
+  }
+
+  static double getDouble(double[] target, long index) {
+    return MEMORY_ACCESSOR.getDouble(
+        target, DOUBLE_ARRAY_BASE_OFFSET + (index * DOUBLE_ARRAY_INDEX_SCALE));
+  }
+
+  static void putDouble(double[] target, long index, double value) {
+    MEMORY_ACCESSOR.putDouble(
+        target, DOUBLE_ARRAY_BASE_OFFSET + (index * DOUBLE_ARRAY_INDEX_SCALE), value);
+  }
+
+  static Object getObject(Object[] target, long index) {
+    return MEMORY_ACCESSOR.getObject(
+        target, OBJECT_ARRAY_BASE_OFFSET + (index * OBJECT_ARRAY_INDEX_SCALE));
+  }
+
+  static void putObject(Object[] target, long index, Object value) {
+    MEMORY_ACCESSOR.putObject(
+        target, OBJECT_ARRAY_BASE_OFFSET + (index * OBJECT_ARRAY_INDEX_SCALE), value);
+  }
+
+  static void copyMemory(byte[] src, long srcIndex, long targetOffset, long length) {
+    MEMORY_ACCESSOR.copyMemory(src, srcIndex, targetOffset, length);
+  }
+
+  static void copyMemory(long srcOffset, byte[] target, long targetIndex, long length) {
+    MEMORY_ACCESSOR.copyMemory(srcOffset, target, targetIndex, length);
+  }
+
+  static void copyMemory(byte[] src, long srcIndex, byte[] target, long targetIndex, long length) {
+    System.arraycopy(src, (int) srcIndex, target, (int) targetIndex, (int) length); 
   }
 
   static byte getByte(long address) {
@@ -221,6 +315,7 @@ final class UnsafeUtil {
       Class<?> clazz = UNSAFE.getClass();
       clazz.getMethod("objectFieldOffset", Field.class);
       clazz.getMethod("arrayBaseOffset", Class.class);
+      clazz.getMethod("arrayIndexScale", Class.class);
       clazz.getMethod("getInt", Object.class, long.class);
       clazz.getMethod("putInt", Object.class, long.class, int.class);
       clazz.getMethod("getLong", Object.class, long.class);
@@ -245,27 +340,6 @@ final class UnsafeUtil {
     return false;
   }
 
-  /**
-   * Indicates whether or not unsafe copyMemory(object, long, object, long, long) operations are
-   * supported on this platform.
-   */
-  private static boolean supportsUnsafeCopyMemory() {
-    if (UNSAFE == null) {
-      return false;
-    }
-    try {
-      Class<?> clazz = UNSAFE.getClass();
-      clazz.getMethod("copyMemory", Object.class, long.class, Object.class, long.class, long.class);
-
-      return true;
-    } catch (Throwable e) {
-      logger.log(
-          Level.WARNING,
-          "copyMemory is missing from platform - proto runtime falling back to safer methods.");
-    }
-    return false;
-  }
-
   private static boolean supportsUnsafeByteBufferOperations() {
     if (UNSAFE == null) {
       return false;
@@ -283,6 +357,7 @@ final class UnsafeUtil {
       clazz.getMethod("getLong", long.class);
       clazz.getMethod("putLong", long.class, long.class);
       clazz.getMethod("copyMemory", long.class, long.class, long.class);
+      clazz.getMethod("copyMemory", Object.class, long.class, Object.class, long.class, long.class);
       return true;
     } catch (Throwable e) {
       logger.log(
@@ -308,13 +383,6 @@ final class UnsafeUtil {
   }
 
   /**
-   * Get the base offset for byte arrays, or {@code -1} if {@code sun.misc.Unsafe} is not available.
-   */
-  private static int byteArrayBaseOffset() {
-    return HAS_UNSAFE_ARRAY_OPERATIONS ? MEMORY_ACCESSOR.arrayBaseOffset(byte[].class) : -1;
-  }
-
-  /**
    * Returns the offset of the provided field, or {@code -1} if {@code sun.misc.Unsafe} is not
    * available.
    */
@@ -394,6 +462,10 @@ final class UnsafeUtil {
       return unsafe.arrayBaseOffset(clazz);
     }
 
+    public final int arrayIndexScale(Class<?> clazz) {
+      return unsafe.arrayIndexScale(clazz);
+    }
+
     public abstract byte getByte(long address);
 
     public abstract void putByte(long address, byte value);
@@ -408,10 +480,11 @@ final class UnsafeUtil {
 
     public abstract void copyMemory(long srcAddress, long targetAddress, long length);
 
-    public abstract void copyMemory(
-        Object src, long srcOffset, Object target, long targetOffset, long length);
-
     public abstract Object getStaticObject(Field field);
+    
+    public abstract void copyMemory(long srcOffset, byte[] target, long targetIndex, long length);
+    
+    public abstract void copyMemory(byte[] src, long srcIndex, long targetOffset, long length);
   }
 
   private static final class JvmMemoryAccessor extends MemoryAccessor {
@@ -491,15 +564,19 @@ final class UnsafeUtil {
     }
 
     @Override
-    public void copyMemory(
-        Object src, long srcOffset, Object target, long targetOffset, long length) {
-      unsafe.copyMemory(src, srcOffset, target, targetOffset, length);
-    }
-
-    @Override
     public void copyMemory(long srcAddress, long targetAddress, long length) {
       unsafe.copyMemory(srcAddress, targetAddress, length);
     }
+    
+    @Override 
+    public void copyMemory(long srcOffset, byte[] target, long targetIndex, long length) {
+      unsafe.copyMemory(null, srcOffset, target, BYTE_ARRAY_BASE_OFFSET + targetIndex, length);
+    }
+    
+    @Override
+    public void copyMemory(byte[] src, long srcIndex, long targetOffset, long length) {
+      unsafe.copyMemory(src, BYTE_ARRAY_BASE_OFFSET + srcIndex, null, targetOffset, length);
+    }
 
     @Override
     public Object getStaticObject(Field field) {
diff --git a/java/core/src/main/java/com/google/protobuf/Utf8.java b/java/core/src/main/java/com/google/protobuf/Utf8.java
index be7b746e..4cf79d7b 100644
--- a/java/core/src/main/java/com/google/protobuf/Utf8.java
+++ b/java/core/src/main/java/com/google/protobuf/Utf8.java
@@ -31,7 +31,6 @@
 package com.google.protobuf;
 
 import static com.google.protobuf.UnsafeUtil.addressOffset;
-import static com.google.protobuf.UnsafeUtil.getArrayBaseOffset;
 import static com.google.protobuf.UnsafeUtil.hasUnsafeArrayOperations;
 import static com.google.protobuf.UnsafeUtil.hasUnsafeByteBufferOperations;
 import static java.lang.Character.MAX_SURROGATE;
@@ -1001,8 +1000,8 @@ final class Utf8 {
         throw new ArrayIndexOutOfBoundsException(
             String.format("Array length=%d, index=%d, limit=%d", bytes.length, index, limit));
       }
-      long offset = getArrayBaseOffset() + index;
-      final long offsetLimit = getArrayBaseOffset() + limit;
+      long offset = index;
+      final long offsetLimit = limit;
       if (state != COMPLETE) {
         // The previous decoding operation was incomplete (or malformed).
         // We look for a well-formed sequence consisting of bytes from
@@ -1187,7 +1186,7 @@ final class Utf8 {
 
     @Override
     int encodeUtf8(final CharSequence in, final byte[] out, final int offset, final int length) {
-      long outIx = getArrayBaseOffset() + offset;
+      long outIx = offset;
       final long outLimit = outIx + length;
       final int inLimit = in.length();
       if (inLimit > length || out.length - length < offset) {
@@ -1204,7 +1203,7 @@ final class Utf8 {
       }
       if (inIx == inLimit) {
         // We're done, it was ASCII encoded.
-        return (int) (outIx - getArrayBaseOffset());
+        return (int) outIx;
       }
 
       for (char c; inIx < inLimit; ++inIx) {
@@ -1243,7 +1242,7 @@ final class Utf8 {
       }
 
       // All bytes have been encoded.
-      return (int) (outIx - getArrayBaseOffset());
+      return (int) outIx;
     }
 
     @Override
@@ -1321,31 +1320,17 @@ final class Utf8 {
      */
     private static int unsafeEstimateConsecutiveAscii(
         byte[] bytes, long offset, final int maxChars) {
-      int remaining = maxChars;
-      if (remaining < UNSAFE_COUNT_ASCII_THRESHOLD) {
+      if (maxChars < UNSAFE_COUNT_ASCII_THRESHOLD) {
         // Don't bother with small strings.
         return 0;
       }
 
-      // Read bytes until 8-byte aligned so that we can read longs in the loop below.
-      // Byte arrays are already either 8 or 16-byte aligned, so we just need to make sure that
-      // the index (relative to the start of the array) is also 8-byte aligned. We do this by
-      // ANDing the index with 7 to determine the number of bytes that need to be read before
-      // we're 8-byte aligned.
-      final int unaligned = 8 - ((int) offset & 7);
-      for (int j = unaligned; j > 0; j--) {
+      for (int i = 0; i < maxChars; i++) {
         if (UnsafeUtil.getByte(bytes, offset++) < 0) {
-          return unaligned - j;
+          return i;
         }
       }
-
-      // This simple loop stops when we encounter a byte >= 0x80 (i.e. non-ASCII).
-      // To speed things up further, we're reading longs instead of bytes so we use a mask to
-      // determine if any byte in the current long is non-ASCII.
-      remaining -= unaligned;
-      for (; remaining >= 8 && (UnsafeUtil.getLong(bytes, offset) & ASCII_MASK_LONG) == 0;
-          offset += 8, remaining -= 8) {}
-      return maxChars - remaining;
+      return maxChars;
     }
 
     /**
diff --git a/java/core/src/main/java/com/google/protobuf/WireFormat.java b/java/core/src/main/java/com/google/protobuf/WireFormat.java
index 0b0cdb7d..8b837ee5 100644
--- a/java/core/src/main/java/com/google/protobuf/WireFormat.java
+++ b/java/core/src/main/java/com/google/protobuf/WireFormat.java
@@ -47,8 +47,10 @@ public final class WireFormat {
   // Do not allow instantiation.
   private WireFormat() {}
 
-  static final int FIXED_32_SIZE = 4;
-  static final int FIXED_64_SIZE = 8;
+  static final int FIXED32_SIZE = 4;
+  static final int FIXED64_SIZE = 8;
+  static final int MAX_VARINT32_SIZE = 5;
+  static final int MAX_VARINT64_SIZE = 10;
   static final int MAX_VARINT_SIZE = 10;
 
   public static final int WIRETYPE_VARINT           = 0;
diff --git a/java/core/src/test/java/com/google/protobuf/CodedInputStreamTest.java b/java/core/src/test/java/com/google/protobuf/CodedInputStreamTest.java
index e440c7db..da2c067e 100644
--- a/java/core/src/test/java/com/google/protobuf/CodedInputStreamTest.java
+++ b/java/core/src/test/java/com/google/protobuf/CodedInputStreamTest.java
@@ -41,6 +41,7 @@ import java.io.FilterInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.nio.ByteBuffer;
+import java.util.Arrays;
 import junit.framework.TestCase;
 
 /**
@@ -613,6 +614,82 @@ public class CodedInputStreamTest extends TestCase {
       checkSizeLimitExceeded(expected);
     }
   }
+  
+  public void testRefillBufferWithCorrectSize() throws Exception {
+    // NOTE: refillBuffer only applies to the stream-backed CIS.
+    byte[] bytes = "123456789".getBytes("UTF-8");
+    ByteArrayOutputStream rawOutput = new ByteArrayOutputStream();
+    CodedOutputStream output = CodedOutputStream.newInstance(rawOutput, bytes.length);
+
+    int tag = WireFormat.makeTag(1, WireFormat.WIRETYPE_LENGTH_DELIMITED);
+    output.writeRawVarint32(tag);
+    output.writeRawVarint32(bytes.length);
+    output.writeRawBytes(bytes);
+    output.writeRawVarint32(tag);
+    output.writeRawVarint32(bytes.length);
+    output.writeRawBytes(bytes);
+    output.writeRawByte(4);
+    output.flush();
+
+    // Input is two string with length 9 and one raw byte.
+    byte[] rawInput = rawOutput.toByteArray(); 
+    for (int inputStreamBufferLength = 8; 
+        inputStreamBufferLength <= rawInput.length + 1; inputStreamBufferLength++) {
+      CodedInputStream input = CodedInputStream.newInstance(
+              new ByteArrayInputStream(rawInput), inputStreamBufferLength);
+      input.setSizeLimit(rawInput.length - 1);
+      input.readString();
+      input.readString(); 
+      try {
+        input.readRawByte(); // Hits limit.
+        fail("Should have thrown an exception!");
+      } catch (InvalidProtocolBufferException expected) {
+        checkSizeLimitExceeded(expected);
+      }
+    }
+  }
+
+  public void testIsAtEnd() throws Exception {
+    CodedInputStream input = CodedInputStream.newInstance(
+        new ByteArrayInputStream(new byte[5]));
+    try {   
+      for (int i = 0; i < 5; i++) {
+        assertEquals(false, input.isAtEnd());
+        input.readRawByte();
+      }
+      assertEquals(true, input.isAtEnd());
+    } catch (Exception e) {
+      fail("Catch exception in the testIsAtEnd");
+    }
+  }
+
+  public void testCurrentLimitExceeded() throws Exception {
+    byte[] bytes = "123456789".getBytes("UTF-8");
+    ByteArrayOutputStream rawOutput = new ByteArrayOutputStream();
+    CodedOutputStream output = CodedOutputStream.newInstance(rawOutput, bytes.length);
+
+    int tag = WireFormat.makeTag(1, WireFormat.WIRETYPE_LENGTH_DELIMITED);
+    output.writeRawVarint32(tag);
+    output.writeRawVarint32(bytes.length);
+    output.writeRawBytes(bytes);
+    output.flush();
+
+    byte[] rawInput = rawOutput.toByteArray();
+    CodedInputStream input = CodedInputStream.newInstance(
+              new ByteArrayInputStream(rawInput));
+    // The length of the whole rawInput
+    input.setSizeLimit(11);
+    // Some number that is smaller than the rawInput's length
+    // but larger than 2 
+    input.pushLimit(5);
+    try {
+      input.readString();
+      fail("Should have thrown an exception");
+    } catch (InvalidProtocolBufferException expected) {
+      assertEquals(expected.getMessage(), 
+          InvalidProtocolBufferException.truncatedMessage().getMessage());
+    }
+  }
 
   public void testSizeLimitMultipleMessages() throws Exception {
     // NOTE: Size limit only applies to the stream-backed CIS.
@@ -807,6 +884,52 @@ public class CodedInputStreamTest extends TestCase {
     }
   }
 
+  public void testReadLargeByteStringFromInputStream() throws Exception {
+    byte[] bytes = new byte[1024 * 1024];
+    for (int i = 0; i < bytes.length; i++) {
+      bytes[i] = (byte) (i & 0xFF);
+    }
+    ByteString.Output rawOutput = ByteString.newOutput();
+    CodedOutputStream output = CodedOutputStream.newInstance(rawOutput);
+    output.writeRawVarint32(bytes.length);
+    output.writeRawBytes(bytes);
+    output.flush();
+    byte[] data = rawOutput.toByteString().toByteArray();
+
+    CodedInputStream input = CodedInputStream.newInstance(
+        new ByteArrayInputStream(data) {
+          @Override
+          public synchronized int available() {
+            return 0;
+          }
+        });
+    ByteString result = input.readBytes();
+    assertEquals(ByteString.copyFrom(bytes), result);
+  }
+
+  public void testReadLargeByteArrayFromInputStream() throws Exception {
+    byte[] bytes = new byte[1024 * 1024];
+    for (int i = 0; i < bytes.length; i++) {
+      bytes[i] = (byte) (i & 0xFF);
+    }
+    ByteString.Output rawOutput = ByteString.newOutput();
+    CodedOutputStream output = CodedOutputStream.newInstance(rawOutput);
+    output.writeRawVarint32(bytes.length);
+    output.writeRawBytes(bytes);
+    output.flush();
+    byte[] data = rawOutput.toByteString().toByteArray();
+
+    CodedInputStream input = CodedInputStream.newInstance(
+        new ByteArrayInputStream(data) {
+          @Override
+          public synchronized int available() {
+            return 0;
+          }
+        });
+    byte[] result = input.readByteArray();
+    assertTrue(Arrays.equals(bytes, result));
+  }
+
   public void testReadByteBuffer() throws Exception {
     ByteString.Output rawOutput = ByteString.newOutput();
     CodedOutputStream output = CodedOutputStream.newInstance(rawOutput);
diff --git a/java/core/src/test/java/com/google/protobuf/DiscardUnknownFieldsTest.java b/java/core/src/test/java/com/google/protobuf/DiscardUnknownFieldsTest.java
new file mode 100644
index 00000000..0f09a51b
--- /dev/null
+++ b/java/core/src/test/java/com/google/protobuf/DiscardUnknownFieldsTest.java
@@ -0,0 +1,157 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import static org.junit.Assert.assertEquals;
+
+import protobuf_unittest.UnittestProto;
+import proto3_unittest.UnittestProto3;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Unit tests for discard or preserve unknown fields. */
+@RunWith(JUnit4.class)
+public class DiscardUnknownFieldsTest {
+  @Test
+  public void testProto2() throws Exception {
+    testProto2Message(
+          UnittestProto.TestEmptyMessage.getDefaultInstance());
+    testProto2Message(
+          UnittestProto.TestEmptyMessageWithExtensions.getDefaultInstance());
+    testProto2Message(
+          DynamicMessage.getDefaultInstance(UnittestProto.TestEmptyMessage.getDescriptor()));
+    testProto2Message(
+          DynamicMessage.getDefaultInstance(
+              UnittestProto.TestEmptyMessageWithExtensions.getDescriptor()));
+  }
+
+  @Test
+  public void testProto3() throws Exception {
+    testProto3Message(UnittestProto3.TestEmptyMessage.getDefaultInstance());
+    testProto3Message(
+        DynamicMessage.getDefaultInstance(UnittestProto3.TestEmptyMessage.getDescriptor()));
+  }
+
+  private static void testProto2Message(Message message) throws Exception {
+    assertUnknownFieldsDefaultPreserved(message);
+    assertUnknownFieldsExplicitlyDiscarded(message);
+    assertReuseCodedInputStreamPreserve(message);
+    assertUnknownFieldsInUnknownFieldSetArePreserve(message);
+  }
+
+  private static void testProto3Message(Message message) throws Exception {
+    CodedInputStream.setProto3KeepUnknownsByDefaultForTest();
+    assertUnknownFieldsDefaultPreserved(message);
+    assertUnknownFieldsExplicitlyDiscarded(message);
+    assertReuseCodedInputStreamPreserve(message);
+    assertUnknownFieldsInUnknownFieldSetArePreserve(message);
+    CodedInputStream.setProto3DiscardUnknownsByDefaultForTest();
+    assertUnknownFieldsDefaultDiscarded(message);
+    assertUnknownFieldsExplicitlyDiscarded(message);
+    assertUnknownFieldsInUnknownFieldSetAreDiscarded(message);
+  }
+
+  private static void assertReuseCodedInputStreamPreserve(Message message) throws Exception {
+    final int messageSize = payload.size();
+    byte[] copied = new byte[messageSize * 2];
+    payload.copyTo(copied, 0);
+    payload.copyTo(copied, messageSize);
+    CodedInputStream input = CodedInputStream.newInstance(copied);
+    {
+      // Use DiscardUnknownFieldsParser to parse the first payload.
+      int oldLimit = input.pushLimit(messageSize);
+      Message parsed = DiscardUnknownFieldsParser.wrap(message.getParserForType()).parseFrom(input);
+      assertEquals(message.getClass().getName(), 0, parsed.getSerializedSize());
+      input.popLimit(oldLimit);
+    }
+    {
+      // Use the normal parser to parse the remaining payload should have unknown fields preserved.
+      Message parsed = message.getParserForType().parseFrom(input);
+      assertEquals(message.getClass().getName(), payload, parsed.toByteString());
+    }
+  }
+
+  /**
+   * {@link Message.Builder#setUnknownFields(UnknownFieldSet)} and {@link
+   * Message.Builder#mergeUnknownFields(UnknownFieldSet)} should preserve the unknown fields.
+   */
+  private static void assertUnknownFieldsInUnknownFieldSetArePreserve(Message message)
+      throws Exception {
+    UnknownFieldSet unknownFields = UnknownFieldSet.newBuilder().mergeFrom(payload).build();
+    Message built = message.newBuilderForType().setUnknownFields(unknownFields).build();
+    assertEquals(message.getClass().getName(), payload, built.toByteString());
+
+  }
+  /**
+   * {@link Message.Builder#setUnknownFields(UnknownFieldSet)} and {@link
+   * Message.Builder#mergeUnknownFields(UnknownFieldSet)} should discard the unknown fields.
+   */
+  private static void assertUnknownFieldsInUnknownFieldSetAreDiscarded(Message message)
+      throws Exception {
+    UnknownFieldSet unknownFields = UnknownFieldSet.newBuilder().mergeFrom(payload).build();
+    Message built = message.newBuilderForType().setUnknownFields(unknownFields).build();
+    assertEquals(message.getClass().getName(), 0, built.getSerializedSize());
+  }
+
+  private static void assertUnknownFieldsDefaultPreserved(MessageLite message) throws Exception {
+    {
+      MessageLite parsed = message.getParserForType().parseFrom(payload);
+      assertEquals(message.getClass().getName(), payload, parsed.toByteString());
+    }
+
+    {
+      MessageLite parsed = message.newBuilderForType().mergeFrom(payload).build();
+      assertEquals(message.getClass().getName(), payload, parsed.toByteString());
+    }
+  }
+
+  private static void assertUnknownFieldsDefaultDiscarded(MessageLite message) throws Exception {
+    {
+      MessageLite parsed = message.getParserForType().parseFrom(payload);
+      assertEquals(message.getClass().getName(), 0, parsed.getSerializedSize());
+    }
+
+    {
+      MessageLite parsed = message.newBuilderForType().mergeFrom(payload).build();
+      assertEquals(message.getClass().getName(), 0, parsed.getSerializedSize());
+    }
+  }
+
+  private static void assertUnknownFieldsExplicitlyDiscarded(Message message) throws Exception {
+    Message parsed =
+        DiscardUnknownFieldsParser.wrap(message.getParserForType()).parseFrom(payload);
+    assertEquals(message.getClass().getName(), 0, parsed.getSerializedSize());
+  }
+
+  private static final ByteString payload =
+      TestUtilLite.getAllLiteSetBuilder().build().toByteString();
+}
diff --git a/java/core/src/test/java/com/google/protobuf/FieldPresenceTest.java b/java/core/src/test/java/com/google/protobuf/FieldPresenceTest.java
index 4a42c897..ff686a0c 100644
--- a/java/core/src/test/java/com/google/protobuf/FieldPresenceTest.java
+++ b/java/core/src/test/java/com/google/protobuf/FieldPresenceTest.java
@@ -108,7 +108,7 @@ public class FieldPresenceTest extends TestCase {
     assertFalse(TestAllTypes.newBuilder().build().hasOptionalNestedMessage());
     assertFalse(TestAllTypes.newBuilder().hasOptionalNestedMessage());
 
-    // oneof fields don't have hasFoo() methods (even for message types).
+    // oneof fields don't have hasFoo() methods for non-message types.
     assertHasMethodRemoved(
         UnittestProto.TestAllTypes.class,
         TestAllTypes.class,
@@ -121,10 +121,8 @@ public class FieldPresenceTest extends TestCase {
         UnittestProto.TestAllTypes.class,
         TestAllTypes.class,
         "OneofBytes");
-    assertHasMethodRemoved(
-        UnittestProto.TestAllTypes.class,
-        TestAllTypes.class,
-        "OneofNestedMessage");
+    assertFalse(TestAllTypes.newBuilder().build().hasOneofNestedMessage());
+    assertFalse(TestAllTypes.newBuilder().hasOneofNestedMessage());
 
     assertHasMethodRemoved(
         UnittestProto.TestAllTypes.Builder.class,
@@ -138,10 +136,6 @@ public class FieldPresenceTest extends TestCase {
         UnittestProto.TestAllTypes.Builder.class,
         TestAllTypes.Builder.class,
         "OneofBytes");
-    assertHasMethodRemoved(
-        UnittestProto.TestAllTypes.Builder.class,
-        TestAllTypes.Builder.class,
-        "OneofNestedMessage");
   }
 
   public void testOneofEquals() throws Exception {
diff --git a/java/core/src/test/java/com/google/protobuf/GeneratedMessageTest.java b/java/core/src/test/java/com/google/protobuf/GeneratedMessageTest.java
index 3eece26a..a4311d17 100644
--- a/java/core/src/test/java/com/google/protobuf/GeneratedMessageTest.java
+++ b/java/core/src/test/java/com/google/protobuf/GeneratedMessageTest.java
@@ -923,15 +923,9 @@ public class GeneratedMessageTest extends TestCase {
   }
 
   public void testEnumValues() {
-     assertEquals(
-         TestAllTypes.NestedEnum.BAR.getNumber(),
-         TestAllTypes.NestedEnum.BAR_VALUE);
-    assertEquals(
-        TestAllTypes.NestedEnum.BAZ.getNumber(),
-        TestAllTypes.NestedEnum.BAZ_VALUE);
-    assertEquals(
-        TestAllTypes.NestedEnum.FOO.getNumber(),
-        TestAllTypes.NestedEnum.FOO_VALUE);
+    assertEquals(TestAllTypes.NestedEnum.BAR_VALUE, TestAllTypes.NestedEnum.BAR.getNumber());
+    assertEquals(TestAllTypes.NestedEnum.BAZ_VALUE, TestAllTypes.NestedEnum.BAZ.getNumber());
+    assertEquals(TestAllTypes.NestedEnum.FOO_VALUE, TestAllTypes.NestedEnum.FOO.getNumber());
   }
 
   public void testNonNestedExtensionInitialization() {
@@ -1319,51 +1313,51 @@ public class GeneratedMessageTest extends TestCase {
       assertFalse(builder.clearFooInt().hasFooInt());
       TestOneof2 message2 = builder.build();
       assertFalse(message2.hasFooInt());
-      assertEquals(message2.getFooInt(), 0);
+      assertEquals(0, message2.getFooInt());
     }
 
     // Enum
     {
       TestOneof2.Builder builder = TestOneof2.newBuilder();
-      assertEquals(builder.getFooEnum(), TestOneof2.NestedEnum.FOO);
+      assertEquals(TestOneof2.NestedEnum.FOO, builder.getFooEnum());
       assertTrue(builder.setFooEnum(TestOneof2.NestedEnum.BAR).hasFooEnum());
-      assertEquals(builder.getFooEnum(), TestOneof2.NestedEnum.BAR);
+      assertEquals(TestOneof2.NestedEnum.BAR, builder.getFooEnum());
       TestOneof2 message = builder.buildPartial();
       assertTrue(message.hasFooEnum());
-      assertEquals(message.getFooEnum(), TestOneof2.NestedEnum.BAR);
+      assertEquals(TestOneof2.NestedEnum.BAR, message.getFooEnum());
 
       assertFalse(builder.clearFooEnum().hasFooEnum());
       TestOneof2 message2 = builder.build();
       assertFalse(message2.hasFooEnum());
-      assertEquals(message2.getFooEnum(), TestOneof2.NestedEnum.FOO);
+      assertEquals(TestOneof2.NestedEnum.FOO, message2.getFooEnum());
     }
 
     // String
     {
       TestOneof2.Builder builder = TestOneof2.newBuilder();
-      assertEquals(builder.getFooString(), "");
+      assertEquals("", builder.getFooString());
       builder.setFooString("foo");
       assertTrue(builder.hasFooString());
-      assertEquals(builder.getFooString(), "foo");
+      assertEquals("foo", builder.getFooString());
       TestOneof2 message = builder.buildPartial();
       assertTrue(message.hasFooString());
-      assertEquals(message.getFooString(), "foo");
+      assertEquals("foo", message.getFooString());
       assertEquals(message.getFooStringBytes(), TestUtil.toBytes("foo"));
 
       assertFalse(builder.clearFooString().hasFooString());
       TestOneof2 message2 = builder.buildPartial();
       assertFalse(message2.hasFooString());
-      assertEquals(message2.getFooString(), "");
+      assertEquals("", message2.getFooString());
       assertEquals(message2.getFooStringBytes(), TestUtil.toBytes(""));
 
       // Get method should not change the oneof value.
       builder.setFooInt(123);
-      assertEquals(builder.getFooString(), "");
+      assertEquals("", builder.getFooString());
       assertEquals(builder.getFooStringBytes(), TestUtil.toBytes(""));
       assertEquals(123, builder.getFooInt());
 
       message = builder.build();
-      assertEquals(message.getFooString(), "");
+      assertEquals("", message.getFooString());
       assertEquals(message.getFooStringBytes(), TestUtil.toBytes(""));
       assertEquals(123, message.getFooInt());
     }
@@ -1371,38 +1365,38 @@ public class GeneratedMessageTest extends TestCase {
     // Cord
     {
       TestOneof2.Builder builder = TestOneof2.newBuilder();
-      assertEquals(builder.getFooCord(), "");
+      assertEquals("", builder.getFooCord());
       builder.setFooCord("foo");
       assertTrue(builder.hasFooCord());
-      assertEquals(builder.getFooCord(), "foo");
+      assertEquals("foo", builder.getFooCord());
       TestOneof2 message = builder.buildPartial();
       assertTrue(message.hasFooCord());
-      assertEquals(message.getFooCord(), "foo");
+      assertEquals("foo", message.getFooCord());
       assertEquals(message.getFooCordBytes(), TestUtil.toBytes("foo"));
 
       assertFalse(builder.clearFooCord().hasFooCord());
       TestOneof2 message2 = builder.build();
       assertFalse(message2.hasFooCord());
-      assertEquals(message2.getFooCord(), "");
+      assertEquals("", message2.getFooCord());
       assertEquals(message2.getFooCordBytes(), TestUtil.toBytes(""));
     }
 
     // StringPiece
     {
       TestOneof2.Builder builder = TestOneof2.newBuilder();
-      assertEquals(builder.getFooStringPiece(), "");
+      assertEquals("", builder.getFooStringPiece());
       builder.setFooStringPiece("foo");
       assertTrue(builder.hasFooStringPiece());
-      assertEquals(builder.getFooStringPiece(), "foo");
+      assertEquals("foo", builder.getFooStringPiece());
       TestOneof2 message = builder.buildPartial();
       assertTrue(message.hasFooStringPiece());
-      assertEquals(message.getFooStringPiece(), "foo");
+      assertEquals("foo", message.getFooStringPiece());
       assertEquals(message.getFooStringPieceBytes(), TestUtil.toBytes("foo"));
 
       assertFalse(builder.clearFooStringPiece().hasFooStringPiece());
       TestOneof2 message2 = builder.build();
       assertFalse(message2.hasFooStringPiece());
-      assertEquals(message2.getFooStringPiece(), "");
+      assertEquals("", message2.getFooStringPiece());
       assertEquals(message2.getFooStringPieceBytes(), TestUtil.toBytes(""));
     }
 
@@ -1410,20 +1404,20 @@ public class GeneratedMessageTest extends TestCase {
     {
       // set
       TestOneof2.Builder builder = TestOneof2.newBuilder();
-      assertEquals(builder.getFooMessage().getQuxInt(), 0);
+      assertEquals(0, builder.getFooMessage().getQuxInt());
       builder.setFooMessage(
           TestOneof2.NestedMessage.newBuilder().setQuxInt(234).build());
       assertTrue(builder.hasFooMessage());
-      assertEquals(builder.getFooMessage().getQuxInt(), 234);
+      assertEquals(234, builder.getFooMessage().getQuxInt());
       TestOneof2 message = builder.buildPartial();
       assertTrue(message.hasFooMessage());
-      assertEquals(message.getFooMessage().getQuxInt(), 234);
+      assertEquals(234, message.getFooMessage().getQuxInt());
 
       // clear
       assertFalse(builder.clearFooMessage().hasFooString());
       message = builder.build();
       assertFalse(message.hasFooMessage());
-      assertEquals(message.getFooMessage().getQuxInt(), 0);
+      assertEquals(0, message.getFooMessage().getQuxInt());
 
       // nested builder
       builder = TestOneof2.newBuilder();
@@ -1432,10 +1426,10 @@ public class GeneratedMessageTest extends TestCase {
       assertFalse(builder.hasFooMessage());
       builder.getFooMessageBuilder().setQuxInt(123);
       assertTrue(builder.hasFooMessage());
-      assertEquals(builder.getFooMessage().getQuxInt(), 123);
+      assertEquals(123, builder.getFooMessage().getQuxInt());
       message = builder.build();
       assertTrue(message.hasFooMessage());
-      assertEquals(message.getFooMessage().getQuxInt(), 123);
+      assertEquals(123, message.getFooMessage().getQuxInt());
     }
 
     // LazyMessage is tested in LazyMessageLiteTest.java
@@ -1448,7 +1442,7 @@ public class GeneratedMessageTest extends TestCase {
       TestOneof2 message = builder.setFooInt(123).build();
       TestOneof2 message2 = TestOneof2.newBuilder().mergeFrom(message).build();
       assertTrue(message2.hasFooInt());
-      assertEquals(message2.getFooInt(), 123);
+      assertEquals(123, message2.getFooInt());
     }
 
     // String
@@ -1457,7 +1451,7 @@ public class GeneratedMessageTest extends TestCase {
       TestOneof2 message = builder.setFooString("foo").build();
       TestOneof2 message2 = TestOneof2.newBuilder().mergeFrom(message).build();
       assertTrue(message2.hasFooString());
-      assertEquals(message2.getFooString(), "foo");
+      assertEquals("foo", message2.getFooString());
     }
 
     // Enum
@@ -1466,7 +1460,7 @@ public class GeneratedMessageTest extends TestCase {
       TestOneof2 message = builder.setFooEnum(TestOneof2.NestedEnum.BAR).build();
       TestOneof2 message2 = TestOneof2.newBuilder().mergeFrom(message).build();
       assertTrue(message2.hasFooEnum());
-      assertEquals(message2.getFooEnum(), TestOneof2.NestedEnum.BAR);
+      assertEquals(TestOneof2.NestedEnum.BAR, message2.getFooEnum());
     }
 
     // Message
@@ -1476,7 +1470,7 @@ public class GeneratedMessageTest extends TestCase {
           TestOneof2.NestedMessage.newBuilder().setQuxInt(234).build()).build();
       TestOneof2 message2 = TestOneof2.newBuilder().mergeFrom(message).build();
       assertTrue(message2.hasFooMessage());
-      assertEquals(message2.getFooMessage().getQuxInt(), 234);
+      assertEquals(234, message2.getFooMessage().getQuxInt());
     }
   }
 
@@ -1488,7 +1482,7 @@ public class GeneratedMessageTest extends TestCase {
       ByteString serialized = message.toByteString();
       TestOneof2 message2 = TestOneof2.parseFrom(serialized);
       assertTrue(message2.hasFooInt());
-      assertEquals(message2.getFooInt(), 123);
+      assertEquals(123, message2.getFooInt());
     }
 
     // String
@@ -1498,7 +1492,7 @@ public class GeneratedMessageTest extends TestCase {
       ByteString serialized = message.toByteString();
       TestOneof2 message2 = TestOneof2.parseFrom(serialized);
       assertTrue(message2.hasFooString());
-      assertEquals(message2.getFooString(), "foo");
+      assertEquals("foo", message2.getFooString());
     }
 
     // Enum
@@ -1508,7 +1502,7 @@ public class GeneratedMessageTest extends TestCase {
       ByteString serialized = message.toByteString();
       TestOneof2 message2 = TestOneof2.parseFrom(serialized);
       assertTrue(message2.hasFooEnum());
-      assertEquals(message2.getFooEnum(), TestOneof2.NestedEnum.BAR);
+      assertEquals(TestOneof2.NestedEnum.BAR, message2.getFooEnum());
     }
 
     // Message
@@ -1519,7 +1513,7 @@ public class GeneratedMessageTest extends TestCase {
       ByteString serialized = message.toByteString();
       TestOneof2 message2 = TestOneof2.parseFrom(serialized);
       assertTrue(message2.hasFooMessage());
-      assertEquals(message2.getFooMessage().getQuxInt(), 234);
+      assertEquals(234, message2.getFooMessage().getQuxInt());
     }
   }
 
diff --git a/java/core/src/test/java/com/google/protobuf/LiteTest.java b/java/core/src/test/java/com/google/protobuf/LiteTest.java
index 98c637a9..ba8bcb1c 100644
--- a/java/core/src/test/java/com/google/protobuf/LiteTest.java
+++ b/java/core/src/test/java/com/google/protobuf/LiteTest.java
@@ -33,6 +33,7 @@ package com.google.protobuf;
 import static java.util.Collections.emptyList;
 import static java.util.Collections.singletonList;
 
+import com.google.protobuf.FieldPresenceTestProto.TestAllTypes;
 import com.google.protobuf.UnittestImportLite.ImportEnumLite;
 import com.google.protobuf.UnittestImportPublicLite.PublicImportMessageLite;
 import com.google.protobuf.UnittestLite.ForeignEnumLite;
@@ -52,7 +53,12 @@ import protobuf_unittest.lite_equals_and_hash.LiteEqualsAndHash.BarPrime;
 import protobuf_unittest.lite_equals_and_hash.LiteEqualsAndHash.Foo;
 import protobuf_unittest.lite_equals_and_hash.LiteEqualsAndHash.TestOneofEquals;
 import protobuf_unittest.lite_equals_and_hash.LiteEqualsAndHash.TestRecursiveOneof;
+import java.lang.reflect.Field;
 import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.List;
 import junit.framework.TestCase;
 
 /**
@@ -155,6 +161,31 @@ public class LiteTest extends TestCase {
       // expected.
     }
   }
+
+  public void testMemoization() throws Exception {
+    TestAllExtensionsLite message = TestUtilLite.getAllLiteExtensionsSet();
+
+    // Test serialized size is memoized
+    message.memoizedSerializedSize = -1;
+    int size = message.getSerializedSize();
+    assertTrue(size > 0);
+    assertEquals(size, message.memoizedSerializedSize);
+
+    // Test hashCode is memoized
+    assertEquals(0, message.memoizedHashCode);
+    int hashCode = message.hashCode();
+    assertTrue(hashCode != 0);
+    assertEquals(hashCode, message.memoizedHashCode);
+
+    // Test isInitialized is memoized
+    Field memo = message.getClass().getDeclaredField("memoizedIsInitialized");
+    memo.setAccessible(true);
+    memo.set(message, (byte) -1);
+    boolean initialized = message.isInitialized();
+    assertTrue(initialized);
+    // We have to cast to Byte first. Casting to byte causes a type error
+    assertEquals(1, ((Byte) memo.get(message)).intValue());
+  }
   
   public void testSanityCopyOnWrite() throws InvalidProtocolBufferException {
     // Since builders are implemented as a thin wrapper around a message
@@ -2378,4 +2409,187 @@ public class LiteTest extends TestCase {
           expected.getUnfinishedMessage());
     }
   }
+
+  // Make sure we haven't screwed up the code generation for packing fields by default.
+  public void testPackedSerialization() throws Exception {
+    TestAllTypes.Builder builder = TestAllTypes.newBuilder();
+    builder.addRepeatedInt32(4321);
+    builder.addRepeatedNestedEnum(TestAllTypes.NestedEnum.BAZ);
+    TestAllTypes message = builder.build();
+
+    CodedInputStream in = CodedInputStream.newInstance(message.toByteArray());
+
+    while (!in.isAtEnd()) {
+      int tag = in.readTag();
+      assertEquals(WireFormat.WIRETYPE_LENGTH_DELIMITED, WireFormat.getTagWireType(tag));
+      in.skipField(tag);
+    }
+  }
+
+  public void testAddAllIteratesOnce() {
+    TestAllTypesLite message =
+        TestAllTypesLite.newBuilder()
+            .addAllRepeatedBool(new OneTimeIterableList(false))
+            .addAllRepeatedInt32(new OneTimeIterableList(0))
+            .addAllRepeatedInt64(new OneTimeIterableList(0L))
+            .addAllRepeatedFloat(new OneTimeIterableList(0f))
+            .addAllRepeatedDouble(new OneTimeIterableList(0d))
+            .addAllRepeatedBytes(new OneTimeIterableList(ByteString.EMPTY))
+            .addAllRepeatedString(new OneTimeIterableList(""))
+            .addAllRepeatedNestedMessage(
+                new OneTimeIterableList(NestedMessage.getDefaultInstance()))
+            .addAllRepeatedBool(new OneTimeIterable(false))
+            .addAllRepeatedInt32(new OneTimeIterable(0))
+            .addAllRepeatedInt64(new OneTimeIterable(0L))
+            .addAllRepeatedFloat(new OneTimeIterable(0f))
+            .addAllRepeatedDouble(new OneTimeIterable(0d))
+            .addAllRepeatedBytes(new OneTimeIterable(ByteString.EMPTY))
+            .addAllRepeatedString(new OneTimeIterable(""))
+            .addAllRepeatedNestedMessage(new OneTimeIterable(NestedMessage.getDefaultInstance()))
+            .build();
+  }
+
+  public void testAddAllIteratesOnce_throwsOnNull() {
+    TestAllTypesLite.Builder builder = TestAllTypesLite.newBuilder();
+    try {
+      builder.addAllRepeatedBool(new OneTimeIterableList(true, false, (Boolean) null));
+      fail();
+    } catch (NullPointerException expected) {
+      assertEquals("Element at index 2 is null.", expected.getMessage());
+      assertEquals(0, builder.getRepeatedBoolCount());
+    }
+
+    try {
+      builder.addAllRepeatedBool(new OneTimeIterable(true, false, (Boolean) null));
+      fail();
+    } catch (NullPointerException expected) {
+      assertEquals("Element at index 2 is null.", expected.getMessage());
+      assertEquals(0, builder.getRepeatedBoolCount());
+    }
+
+    try {
+      builder = TestAllTypesLite.newBuilder();
+      builder.addAllRepeatedBool(new OneTimeIterableList((Boolean) null));
+      fail();
+    } catch (NullPointerException expected) {
+      assertEquals("Element at index 0 is null.", expected.getMessage());
+      assertEquals(0, builder.getRepeatedBoolCount());
+    }
+
+    try {
+      builder = TestAllTypesLite.newBuilder();
+      builder.addAllRepeatedInt32(new OneTimeIterableList((Integer) null));
+      fail();
+    } catch (NullPointerException expected) {
+      assertEquals("Element at index 0 is null.", expected.getMessage());
+      assertEquals(0, builder.getRepeatedInt32Count());
+    }
+
+    try {
+      builder = TestAllTypesLite.newBuilder();
+      builder.addAllRepeatedInt64(new OneTimeIterableList((Long) null));
+      fail();
+    } catch (NullPointerException expected) {
+      assertEquals("Element at index 0 is null.", expected.getMessage());
+      assertEquals(0, builder.getRepeatedInt64Count());
+    }
+
+    try {
+      builder = TestAllTypesLite.newBuilder();
+      builder.addAllRepeatedFloat(new OneTimeIterableList((Float) null));
+      fail();
+    } catch (NullPointerException expected) {
+      assertEquals("Element at index 0 is null.", expected.getMessage());
+      assertEquals(0, builder.getRepeatedFloatCount());
+    }
+
+    try {
+      builder = TestAllTypesLite.newBuilder();
+      builder.addAllRepeatedDouble(new OneTimeIterableList((Double) null));
+      fail();
+    } catch (NullPointerException expected) {
+      assertEquals("Element at index 0 is null.", expected.getMessage());
+      assertEquals(0, builder.getRepeatedDoubleCount());
+    }
+
+    try {
+      builder = TestAllTypesLite.newBuilder();
+      builder.addAllRepeatedBytes(new OneTimeIterableList((ByteString) null));
+      fail();
+    } catch (NullPointerException expected) {
+      assertEquals("Element at index 0 is null.", expected.getMessage());
+      assertEquals(0, builder.getRepeatedBytesCount());
+    }
+
+    try {
+      builder = TestAllTypesLite.newBuilder();
+      builder.addAllRepeatedString(new OneTimeIterableList("", "", (String) null, ""));
+      fail();
+    } catch (NullPointerException expected) {
+      assertEquals("Element at index 2 is null.", expected.getMessage());
+      assertEquals(0, builder.getRepeatedStringCount());
+    }
+
+    try {
+      builder = TestAllTypesLite.newBuilder();
+      builder.addAllRepeatedString(new OneTimeIterable("", "", (String) null, ""));
+      fail();
+    } catch (NullPointerException expected) {
+      assertEquals("Element at index 2 is null.", expected.getMessage());
+      assertEquals(0, builder.getRepeatedStringCount());
+    }
+
+    try {
+      builder = TestAllTypesLite.newBuilder();
+      builder.addAllRepeatedString(new OneTimeIterableList((String) null));
+      fail();
+    } catch (NullPointerException expected) {
+      assertEquals("Element at index 0 is null.", expected.getMessage());
+      assertEquals(0, builder.getRepeatedStringCount());
+    }
+
+    try {
+      builder = TestAllTypesLite.newBuilder();
+      builder.addAllRepeatedNestedMessage(new OneTimeIterableList((NestedMessage) null));
+      fail();
+    } catch (NullPointerException expected) {
+      assertEquals("Element at index 0 is null.", expected.getMessage());
+      assertEquals(0, builder.getRepeatedNestedMessageCount());
+    }
+  }
+
+  private static final class OneTimeIterableList<T> extends ArrayList<T> {
+    private boolean wasIterated = false;
+
+    OneTimeIterableList(T... contents) {
+      addAll(Arrays.asList(contents));
+    }
+
+    @Override
+    public Iterator<T> iterator() {
+      if (wasIterated) {
+        fail();
+      }
+      wasIterated = true;
+      return super.iterator();
+    }
+  }
+
+  private static final class OneTimeIterable<T> implements Iterable<T> {
+    private final List<T> list;
+    private boolean wasIterated = false;
+
+    OneTimeIterable(T... contents) {
+      list = Arrays.asList(contents);
+    }
+
+    @Override
+    public Iterator<T> iterator() {
+      if (wasIterated) {
+        fail();
+      }
+      wasIterated = true;
+      return list.iterator();
+    }
+  }
 }
diff --git a/java/core/src/test/java/com/google/protobuf/MapForProto2LiteTest.java b/java/core/src/test/java/com/google/protobuf/MapForProto2LiteTest.java
index 0a14f584..da9195f9 100644
--- a/java/core/src/test/java/com/google/protobuf/MapForProto2LiteTest.java
+++ b/java/core/src/test/java/com/google/protobuf/MapForProto2LiteTest.java
@@ -408,12 +408,12 @@ public final class MapForProto2LiteTest extends TestCase {
     TestMap map = tryParseTestMap(BizarroTestMap.newBuilder()
         .putInt32ToInt32Field(5, bytes)
         .build());
-    assertEquals(map.getInt32ToInt32FieldOrDefault(5, -1), 0);
+    assertEquals(0, map.getInt32ToInt32FieldOrDefault(5, -1));
 
     map = tryParseTestMap(BizarroTestMap.newBuilder()
         .putInt32ToStringField(stringKey, 5)
         .build());
-    assertEquals(map.getInt32ToStringFieldOrDefault(0, null), "");
+    assertEquals("", map.getInt32ToStringFieldOrDefault(0, null));
 
     map = tryParseTestMap(BizarroTestMap.newBuilder()
         .putInt32ToBytesField(stringKey, 5)
@@ -423,7 +423,7 @@ public final class MapForProto2LiteTest extends TestCase {
     map = tryParseTestMap(BizarroTestMap.newBuilder()
         .putInt32ToEnumField(stringKey, bytes)
         .build());
-    assertEquals(map.getInt32ToEnumFieldOrDefault(0, null), TestMap.EnumValue.FOO);
+    assertEquals(TestMap.EnumValue.FOO, map.getInt32ToEnumFieldOrDefault(0, null));
 
     try {
       tryParseTestMap(BizarroTestMap.newBuilder()
@@ -439,7 +439,7 @@ public final class MapForProto2LiteTest extends TestCase {
     map = tryParseTestMap(BizarroTestMap.newBuilder()
         .putStringToInt32Field(stringKey, bytes)
         .build());
-    assertEquals(map.getStringToInt32FieldOrDefault(stringKey, -1), 0);
+    assertEquals(0, map.getStringToInt32FieldOrDefault(stringKey, -1));
   }
 
   public void testMergeFrom() throws Exception {
diff --git a/java/core/src/test/java/com/google/protobuf/MapForProto2Test.java b/java/core/src/test/java/com/google/protobuf/MapForProto2Test.java
index 453d3928..37827f76 100644
--- a/java/core/src/test/java/com/google/protobuf/MapForProto2Test.java
+++ b/java/core/src/test/java/com/google/protobuf/MapForProto2Test.java
@@ -546,12 +546,12 @@ public class MapForProto2Test extends TestCase {
     TestMap map = tryParseTestMap(BizarroTestMap.newBuilder()
         .putInt32ToInt32Field(5, bytes)
         .build());
-    assertEquals(map.getInt32ToInt32FieldOrDefault(5, -1), 0);
+    assertEquals(0, map.getInt32ToInt32FieldOrDefault(5, -1));
 
     map = tryParseTestMap(BizarroTestMap.newBuilder()
         .putInt32ToStringField(stringKey, 5)
         .build());
-    assertEquals(map.getInt32ToStringFieldOrDefault(0, null), "");
+    assertEquals("", map.getInt32ToStringFieldOrDefault(0, null));
 
     map = tryParseTestMap(BizarroTestMap.newBuilder()
         .putInt32ToBytesField(stringKey, 5)
@@ -561,7 +561,7 @@ public class MapForProto2Test extends TestCase {
     map = tryParseTestMap(BizarroTestMap.newBuilder()
         .putInt32ToEnumField(stringKey, bytes)
         .build());
-    assertEquals(map.getInt32ToEnumFieldOrDefault(0, null), TestMap.EnumValue.FOO);
+    assertEquals(TestMap.EnumValue.FOO, map.getInt32ToEnumFieldOrDefault(0, null));
 
     try {
       tryParseTestMap(BizarroTestMap.newBuilder()
@@ -577,7 +577,7 @@ public class MapForProto2Test extends TestCase {
     map = tryParseTestMap(BizarroTestMap.newBuilder()
         .putStringToInt32Field(stringKey, bytes)
         .build());
-    assertEquals(map.getStringToInt32FieldOrDefault(stringKey, -1), 0);
+    assertEquals(0, map.getStringToInt32FieldOrDefault(stringKey, -1));
   }
 
   public void testMergeFrom() throws Exception {
diff --git a/java/core/src/test/java/com/google/protobuf/MapTest.java b/java/core/src/test/java/com/google/protobuf/MapTest.java
index 45019537..64ae4435 100644
--- a/java/core/src/test/java/com/google/protobuf/MapTest.java
+++ b/java/core/src/test/java/com/google/protobuf/MapTest.java
@@ -576,12 +576,12 @@ public class MapTest extends TestCase {
     TestMap map = tryParseTestMap(BizarroTestMap.newBuilder()
         .putInt32ToInt32Field(5, bytes)
         .build());
-    assertEquals(map.getInt32ToInt32FieldOrDefault(5, -1), 0);
+    assertEquals(0, map.getInt32ToInt32FieldOrDefault(5, -1));
 
     map = tryParseTestMap(BizarroTestMap.newBuilder()
         .putInt32ToStringField(stringKey, 5)
         .build());
-    assertEquals(map.getInt32ToStringFieldOrDefault(0, null), "");
+    assertEquals("", map.getInt32ToStringFieldOrDefault(0, null));
 
     map = tryParseTestMap(BizarroTestMap.newBuilder()
         .putInt32ToBytesField(stringKey, 5)
@@ -591,7 +591,7 @@ public class MapTest extends TestCase {
     map = tryParseTestMap(BizarroTestMap.newBuilder()
         .putInt32ToEnumField(stringKey, bytes)
         .build());
-    assertEquals(map.getInt32ToEnumFieldOrDefault(0, null), TestMap.EnumValue.FOO);
+    assertEquals(TestMap.EnumValue.FOO, map.getInt32ToEnumFieldOrDefault(0, null));
 
     try {
       tryParseTestMap(BizarroTestMap.newBuilder()
@@ -607,7 +607,7 @@ public class MapTest extends TestCase {
     map = tryParseTestMap(BizarroTestMap.newBuilder()
         .putStringToInt32Field(stringKey, bytes)
         .build());
-    assertEquals(map.getStringToInt32FieldOrDefault(stringKey, -1), 0);
+    assertEquals(0, map.getStringToInt32FieldOrDefault(stringKey, -1));
   }
 
   public void testMergeFrom() throws Exception {
diff --git a/java/core/src/test/java/com/google/protobuf/MessageTest.java b/java/core/src/test/java/com/google/protobuf/MessageTest.java
index 75b79a34..9d55d0dd 100644
--- a/java/core/src/test/java/com/google/protobuf/MessageTest.java
+++ b/java/core/src/test/java/com/google/protobuf/MessageTest.java
@@ -321,8 +321,10 @@ public class MessageTest extends TestCase {
 
     assertTrue(result.getField(result.getDescriptorForType()
         .findFieldByName("repeated_foreign_message")) instanceof List<?>);
-    assertEquals(result.getRepeatedFieldCount(result.getDescriptorForType()
-        .findFieldByName("repeated_foreign_message")), 0);
+    assertEquals(
+        0,
+        result.getRepeatedFieldCount(
+            result.getDescriptorForType().findFieldByName("repeated_foreign_message")));
   }
   
   /** Test reading repeated message from DynamicMessage. */
@@ -345,7 +347,9 @@ public class MessageTest extends TestCase {
 
     assertTrue(result.getField(result.getDescriptorForType()
         .findFieldByName("repeated_foreign_message")) instanceof List<?>);
-    assertEquals(result.getRepeatedFieldCount(result.getDescriptorForType()
-        .findFieldByName("repeated_foreign_message")), 2);
+    assertEquals(
+        2,
+        result.getRepeatedFieldCount(
+            result.getDescriptorForType().findFieldByName("repeated_foreign_message")));
   }
 }
diff --git a/java/core/src/test/java/com/google/protobuf/TestBadIdentifiers.java b/java/core/src/test/java/com/google/protobuf/TestBadIdentifiers.java
index 2c60fe0e..4af55429 100644
--- a/java/core/src/test/java/com/google/protobuf/TestBadIdentifiers.java
+++ b/java/core/src/test/java/com/google/protobuf/TestBadIdentifiers.java
@@ -92,5 +92,31 @@ public class TestBadIdentifiers extends TestCase {
     assertEquals(0L, message.getExtension(
         TestBadIdentifiersProto.TestConflictingFieldNames.int64FieldList).longValue());
 
+    assertEquals("", message.getFieldName32());
+    assertEquals("", message.getFieldName33());
+    assertEquals(0, message.get2Conflict34());
+    assertEquals(0, message.get2Conflict35());
+
+  }
+
+  public void testNumberFields() throws Exception {
+    TestBadIdentifiersProto.TestLeadingNumberFields message =
+        TestBadIdentifiersProto.TestLeadingNumberFields.getDefaultInstance();
+    // Make sure generated accessors are properly named.
+    assertFalse(message.has30DayImpressions());
+    assertEquals(0, message.get30DayImpressions());
+    assertEquals(0, message.get60DayImpressionsCount());
+    assertEquals(0, message.get60DayImpressionsList().size());
+
+    assertFalse(message.has2Underscores());
+    assertEquals("", message.get2Underscores());
+    assertEquals(0, message.get2RepeatedUnderscoresCount());
+    assertEquals(0, message.get2RepeatedUnderscoresList().size());
+
+    assertFalse(message.has32());
+    assertEquals(0, message.get32());
+    assertEquals(0, message.get64Count());
+    assertEquals(0, message.get64List().size());
+
   }
 }
diff --git a/java/core/src/test/java/com/google/protobuf/TestBadIdentifiersLite.java b/java/core/src/test/java/com/google/protobuf/TestBadIdentifiersLite.java
new file mode 100644
index 00000000..37f94c03
--- /dev/null
+++ b/java/core/src/test/java/com/google/protobuf/TestBadIdentifiersLite.java
@@ -0,0 +1,83 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import junit.framework.TestCase;
+
+/**
+ * Tests that proto2 api generation doesn't cause compile errors when compiling protocol buffers
+ * that have names that would otherwise conflict if not fully qualified (like @Deprecated
+ * and @Override).
+ *
+ * <p>Forked from {@link TestBadIdentifiers}.
+ *
+ * @author jonp@google.com (Jon Perlow)
+ */
+public final class TestBadIdentifiersLite extends TestCase {
+
+  public void testCompilation() {
+    // If this compiles, it means the generation was correct.
+    TestBadIdentifiersProto.Deprecated.newBuilder();
+    TestBadIdentifiersProto.Override.newBuilder();
+  }
+
+  public void testConflictingFieldNames() throws Exception {
+    TestBadIdentifiersProto.TestConflictingFieldNames message =
+        TestBadIdentifiersProto.TestConflictingFieldNames.getDefaultInstance();
+    // Make sure generated accessors are properly named.
+    assertEquals(0, message.getInt32Field1Count());
+    assertEquals(0, message.getEnumField2Count());
+    assertEquals(0, message.getStringField3Count());
+    assertEquals(0, message.getBytesField4Count());
+    assertEquals(0, message.getMessageField5Count());
+
+    assertEquals(0, message.getInt32FieldCount11());
+    assertEquals(0, message.getEnumFieldCount12().getNumber());
+    assertEquals("", message.getStringFieldCount13());
+    assertEquals(ByteString.EMPTY, message.getBytesFieldCount14());
+    assertEquals(0, message.getMessageFieldCount15().getSerializedSize());
+
+    assertEquals(0, message.getInt32Field21Count());
+    assertEquals(0, message.getEnumField22Count());
+    assertEquals(0, message.getStringField23Count());
+    assertEquals(0, message.getBytesField24Count());
+    assertEquals(0, message.getMessageField25Count());
+
+    assertEquals(0, message.getInt32Field1List().size());
+    assertEquals(0, message.getInt32FieldList31());
+
+    assertEquals(0, message.getInt64FieldCount());
+    assertEquals(0L, message.getExtension(
+        TestBadIdentifiersProto.TestConflictingFieldNames.int64FieldCount).longValue());
+    assertEquals(0L, message.getExtension(
+        TestBadIdentifiersProto.TestConflictingFieldNames.int64FieldList).longValue());
+  }
+}
diff --git a/java/core/src/test/java/com/google/protobuf/TextFormatTest.java b/java/core/src/test/java/com/google/protobuf/TextFormatTest.java
index 249d7c5e..910f360f 100644
--- a/java/core/src/test/java/com/google/protobuf/TextFormatTest.java
+++ b/java/core/src/test/java/com/google/protobuf/TextFormatTest.java
@@ -30,8 +30,6 @@
 
 package com.google.protobuf;
 
-import static com.google.common.truth.Truth.assertThat;
-
 import com.google.protobuf.Descriptors.Descriptor;
 import com.google.protobuf.Descriptors.FieldDescriptor;
 import com.google.protobuf.TextFormat.Parser.SingularOverwritePolicy;
@@ -1079,12 +1077,12 @@ public class TextFormatTest extends TestCase {
     {
       TestMap.Builder dest = TestMap.newBuilder();
       TextFormat.merge(text, dest);
-      assertThat(dest.build()).isEqualTo(message);
+      assertEquals(message, dest.build());
     }
     {
       TestMap.Builder dest = TestMap.newBuilder();
       parserWithOverwriteForbidden.merge(text, dest);
-      assertThat(dest.build()).isEqualTo(message);
+      assertEquals(message, dest.build());
     }
   }
 
@@ -1096,10 +1094,10 @@ public class TextFormatTest extends TestCase {
     TestMap.Builder dest = TestMap.newBuilder();
     parserWithOverwriteForbidden.merge(text, dest);
     TestMap message = dest.build();
-    assertThat(message.getStringToInt32Field().size()).isEqualTo(2);
-    assertThat(message.getInt32ToMessageField().size()).isEqualTo(2);
-    assertThat(message.getStringToInt32Field().get("x")).isEqualTo(10);
-    assertThat(message.getInt32ToMessageField().get(2).getValue()).isEqualTo(200);
+    assertEquals(2, message.getStringToInt32Field().size());
+    assertEquals(2, message.getInt32ToMessageField().size());
+    assertEquals(10, message.getStringToInt32Field().get("x").intValue());
+    assertEquals(200, message.getInt32ToMessageField().get(2).getValue());
   }
 
   public void testMapShortFormEmpty() throws Exception {
@@ -1108,8 +1106,8 @@ public class TextFormatTest extends TestCase {
     TestMap.Builder dest = TestMap.newBuilder();
     parserWithOverwriteForbidden.merge(text, dest);
     TestMap message = dest.build();
-    assertThat(message.getStringToInt32Field().size()).isEqualTo(0);
-    assertThat(message.getInt32ToMessageField().size()).isEqualTo(0);
+    assertEquals(0, message.getStringToInt32Field().size());
+    assertEquals(0, message.getInt32ToMessageField().size());
   }
 
   public void testMapShortFormTrailingComma() throws Exception {
@@ -1119,7 +1117,7 @@ public class TextFormatTest extends TestCase {
       parserWithOverwriteForbidden.merge(text, dest);
       fail("Expected parse exception.");
     } catch (TextFormat.ParseException e) {
-      assertThat(e).hasMessageThat().isEqualTo("1:48: Expected \"{\".");
+      assertEquals("1:48: Expected \"{\".", e.getMessage());
     }
   }
 
@@ -1134,8 +1132,8 @@ public class TextFormatTest extends TestCase {
       TestMap.Builder builder = TestMap.newBuilder();
       defaultParser.merge(text, builder);
       TestMap map = builder.build();
-      assertThat(map.getInt32ToInt32Field().size()).isEqualTo(2);
-      assertThat(map.getInt32ToInt32Field().get(1).intValue()).isEqualTo(30);
+      assertEquals(2, map.getInt32ToInt32Field().size());
+      assertEquals(30, map.getInt32ToInt32Field().get(1).intValue());
     }
 
     {
@@ -1144,8 +1142,8 @@ public class TextFormatTest extends TestCase {
       TestMap.Builder builder = TestMap.newBuilder();
       defaultParser.merge(text, builder);
       TestMap map = builder.build();
-      assertThat(map.getInt32ToInt32Field().size()).isEqualTo(2);
-      assertThat(map.getInt32ToInt32Field().get(1).intValue()).isEqualTo(30);
+      assertEquals(2, map.getInt32ToInt32Field().size());
+      assertEquals(30, map.getInt32ToInt32Field().get(1).intValue());
     }
   }
 
diff --git a/java/core/src/test/java/com/google/protobuf/UnknownEnumValueTest.java b/java/core/src/test/java/com/google/protobuf/UnknownEnumValueTest.java
index 8f45976f..88cbbf86 100644
--- a/java/core/src/test/java/com/google/protobuf/UnknownEnumValueTest.java
+++ b/java/core/src/test/java/com/google/protobuf/UnknownEnumValueTest.java
@@ -36,7 +36,6 @@ import com.google.protobuf.Descriptors.EnumValueDescriptor;
 import com.google.protobuf.Descriptors.FieldDescriptor;
 import com.google.protobuf.FieldPresenceTestProto.TestAllTypes;
 import com.google.protobuf.TextFormat.ParseException;
-
 import junit.framework.TestCase;
 
 /**
@@ -151,18 +150,15 @@ public class UnknownEnumValueTest extends TestCase {
     assertEquals(4321, unknown4321.getNumber());
     assertEquals(5432, unknown5432.getNumber());
     assertEquals(6543, unknown6543.getNumber());
-    
+
     // Unknown EnumValueDescriptor will map to UNRECOGNIZED.
     assertEquals(
-        TestAllTypes.NestedEnum.valueOf(unknown4321),
-        TestAllTypes.NestedEnum.UNRECOGNIZED);
+        TestAllTypes.NestedEnum.UNRECOGNIZED, TestAllTypes.NestedEnum.valueOf(unknown4321));
     assertEquals(
-        TestAllTypes.NestedEnum.valueOf(unknown5432),
-        TestAllTypes.NestedEnum.UNRECOGNIZED);
+        TestAllTypes.NestedEnum.UNRECOGNIZED, TestAllTypes.NestedEnum.valueOf(unknown5432));
     assertEquals(
-        TestAllTypes.NestedEnum.valueOf(unknown6543),
-        TestAllTypes.NestedEnum.UNRECOGNIZED);
-    
+        TestAllTypes.NestedEnum.UNRECOGNIZED, TestAllTypes.NestedEnum.valueOf(unknown6543));
+
     // Setters also accept unknown EnumValueDescriptor.
     builder.setField(optionalNestedEnumField, unknown6543);
     builder.setRepeatedField(repeatedNestedEnumField, 0, unknown4321);
diff --git a/java/core/src/test/proto/com/google/protobuf/test_bad_identifiers.proto b/java/core/src/test/proto/com/google/protobuf/test_bad_identifiers.proto
index d2c77936..ff5bf3ae 100644
--- a/java/core/src/test/proto/com/google/protobuf/test_bad_identifiers.proto
+++ b/java/core/src/test/proto/com/google/protobuf/test_bad_identifiers.proto
@@ -148,6 +148,12 @@ message TestConflictingFieldNames {
   // the method getInt32FieldList().
   required int32 int32_field_list = 31;  // NO_PROTO3
 
+  // These field pairs have the same Java converted name
+  optional string field_name = 32; // NO_PROTO3
+  optional string field__name = 33; // NO_PROTO3
+  optional int32 _2conflict = 34; // NO_PROTO3
+  optional int32 __2conflict = 35;
+
   extensions 1000 to max;  // NO_PROTO3
 
   repeated int64 int64_field = 41;
@@ -166,3 +172,14 @@ message TestMapField {
 
   map<int32, int32> map_field = 1;
 }
+
+message TestLeadingNumberFields {
+  optional int32 _30day_impressions = 1;
+  repeated string _60day_impressions = 2;
+
+  optional string __2_underscores = 3;
+  repeated string __2repeated_underscores = 4;
+
+  optional int32 _32 = 32;
+  repeated int64 _64 = 64;
+}
diff --git a/java/util/src/main/java/com/google/protobuf/util/Durations.java b/java/util/src/main/java/com/google/protobuf/util/Durations.java
index 46b21828..dc223d47 100644
--- a/java/util/src/main/java/com/google/protobuf/util/Durations.java
+++ b/java/util/src/main/java/com/google/protobuf/util/Durations.java
@@ -84,6 +84,17 @@ public final class Durations {
   }
 
   /**
+   * Compares two durations. The value returned is identical to what would be returned by:
+   * {@code Durations.comparator().compare(x, y)}.
+   *
+   * @return the value {@code 0} if {@code x == y}; a value less than {@code 0} if {@code x < y};
+   *     and a value greater than {@code 0} if {@code x > y}
+   */
+  public static int compare(Duration x, Duration y) {
+    return COMPARATOR.compare(x, y);
+  }
+
+  /**
    * Returns true if the given {@link Duration} is valid. The {@code seconds} value must be in the
    * range [-315,576,000,000, +315,576,000,000]. The {@code nanos} value must be in the range
    * [-999,999,999, +999,999,999].
diff --git a/java/util/src/main/java/com/google/protobuf/util/FieldMaskUtil.java b/java/util/src/main/java/com/google/protobuf/util/FieldMaskUtil.java
index 21d11b2c..b2f849c4 100644
--- a/java/util/src/main/java/com/google/protobuf/util/FieldMaskUtil.java
+++ b/java/util/src/main/java/com/google/protobuf/util/FieldMaskUtil.java
@@ -311,16 +311,19 @@ public class FieldMaskUtil {
       return replacePrimitiveFields;
     }
 
-    public void setReplaceMessageFields(boolean value) {
+    public MergeOptions setReplaceMessageFields(boolean value) {
       replaceMessageFields = value;
+      return this;
     }
 
-    public void setReplaceRepeatedFields(boolean value) {
+    public MergeOptions setReplaceRepeatedFields(boolean value) {
       replaceRepeatedFields = value;
+      return this;
     }
 
-    public void setReplacePrimitiveFields(boolean value) {
+    public MergeOptions setReplacePrimitiveFields(boolean value) {
       replacePrimitiveFields = value;
+      return this;
     }
   }
 
diff --git a/java/util/src/main/java/com/google/protobuf/util/JsonFormat.java b/java/util/src/main/java/com/google/protobuf/util/JsonFormat.java
index e1c2d73d..a603d96a 100644
--- a/java/util/src/main/java/com/google/protobuf/util/JsonFormat.java
+++ b/java/util/src/main/java/com/google/protobuf/util/JsonFormat.java
@@ -1686,7 +1686,11 @@ public class JsonFormat {
     }
 
     private ByteString parseBytes(JsonElement json) throws InvalidProtocolBufferException {
-      return ByteString.copyFrom(BaseEncoding.base64().decode(json.getAsString()));
+      try {
+        return ByteString.copyFrom(BaseEncoding.base64().decode(json.getAsString()));
+      } catch (IllegalArgumentException e) {
+        return ByteString.copyFrom(BaseEncoding.base64Url().decode(json.getAsString()));
+      }
     }
 
     private EnumValueDescriptor parseEnum(EnumDescriptor enumDescriptor, JsonElement json)
diff --git a/java/util/src/main/java/com/google/protobuf/util/Timestamps.java b/java/util/src/main/java/com/google/protobuf/util/Timestamps.java
index d0bac417..13136f30 100644
--- a/java/util/src/main/java/com/google/protobuf/util/Timestamps.java
+++ b/java/util/src/main/java/com/google/protobuf/util/Timestamps.java
@@ -115,6 +115,17 @@ public final class Timestamps {
   }
 
   /**
+   * Compares two timestamps. The value returned is identical to what would be returned by:
+   * {@code Timestamps.comparator().compare(x, y)}.
+   *
+   * @return the value {@code 0} if {@code x == y}; a value less than {@code 0} if {@code x < y};
+   *     and a value greater than {@code 0} if {@code x > y}
+   */
+  public static int compare(Timestamp x, Timestamp y) {
+    return COMPARATOR.compare(x, y);
+  }
+
+  /**
    * Returns true if the given {@link Timestamp} is valid. The {@code seconds} value must be in the
    * range [-62,135,596,800, +253,402,300,799] (i.e., between 0001-01-01T00:00:00Z and
    * 9999-12-31T23:59:59Z). The {@code nanos} value must be in the range [0, +999,999,999].
diff --git a/java/util/src/test/java/com/google/protobuf/util/JsonFormatTest.java b/java/util/src/test/java/com/google/protobuf/util/JsonFormatTest.java
index 460b81f6..e4c5387a 100644
--- a/java/util/src/test/java/com/google/protobuf/util/JsonFormatTest.java
+++ b/java/util/src/test/java/com/google/protobuf/util/JsonFormatTest.java
@@ -73,7 +73,6 @@ import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Locale;
-import java.util.Map;
 import java.util.Set;
 import junit.framework.TestCase;
 
@@ -1144,7 +1143,8 @@ public class JsonFormatTest extends TestCase {
   }
 
   public void testParserAcceptBase64Variants() throws Exception {
-    assertAccepts("optionalBytes", "AQI");
+    assertAccepts("optionalBytes", "AQI");  // No padding
+    assertAccepts("optionalBytes", "-_w");  // base64Url, no padding
   }
 
   public void testParserRejectInvalidEnumValue() throws Exception {