down integrate to svn

1 files changed, 89 insertions, 5 deletions

diff --git a/src/google/protobuf/io/coded_stream.h b/src/google/protobuf/io/coded_stream.h
index 66cbee00..50a03a11 100644
--- a/src/google/protobuf/io/coded_stream.h
+++ b/src/google/protobuf/io/coded_stream.h
@@ -233,11 +233,22 @@ class LIBPROTOBUF_EXPORT CodedInputStream {
   // Read a tag.  This calls ReadVarint32() and returns the result, or returns
   // zero (which is not a valid tag) if ReadVarint32() fails.  Also, it updates
   // the last tag value, which can be checked with LastTagWas().
-  // Always inline because this is only called in once place per parse loop
+  // Always inline because this is only called in one place per parse loop
   // but it is called for every iteration of said loop, so it should be fast.
   // GCC doesn't want to inline this by default.
   uint32 ReadTag() GOOGLE_ATTRIBUTE_ALWAYS_INLINE;
 
+  // This usually a faster alternative to ReadTag() when cutoff is a manifest
+  // constant.  It does particularly well for cutoff >= 127.  The first part
+  // of the return value is the tag that was read, though it can also be 0 in
+  // the cases where ReadTag() would return 0.  If the second part is true
+  // then the tag is known to be in [0, cutoff].  If not, the tag either is
+  // above cutoff or is 0.  (There's intentional wiggle room when tag is 0,
+  // because that can arise in several ways, and for best performance we want
+  // to avoid an extra "is tag == 0?" check here.)
+  inline std::pair<uint32, bool> ReadTagWithCutoff(uint32 cutoff)
+      GOOGLE_ATTRIBUTE_ALWAYS_INLINE;
+
   // Usually returns true if calling ReadVarint32() now would produce the given
   // value.  Will always return false if ReadVarint32() would not return the
   // given value.  If ExpectTag() returns true, it also advances past
@@ -264,8 +275,8 @@ class LIBPROTOBUF_EXPORT CodedInputStream {
   // zero, and ConsumedEntireMessage() will return true.
   bool ExpectAtEnd();
 
-  // If the last call to ReadTag() returned the given value, returns true.
-  // Otherwise, returns false;
+  // If the last call to ReadTag() or ReadTagWithCutoff() returned the
+  // given value, returns true.  Otherwise, returns false;
   //
   // This is needed because parsers for some types of embedded messages
   // (with field type TYPE_GROUP) don't actually know that they've reached the
@@ -333,7 +344,7 @@ class LIBPROTOBUF_EXPORT CodedInputStream {
   // cause integer overflows is 512MB.  The default limit is 64MB.  Apps
   // should set shorter limits if possible.  If warning_threshold is not -1,
   // a warning will be printed to stderr after warning_threshold bytes are
-  // read.  For backwards compatibility all negative values get squached to -1,
+  // read.  For backwards compatibility all negative values get squashed to -1,
   // as other negative values might have special internal meanings.
   // An error will always be printed to stderr if the limit is reached.
   //
@@ -356,6 +367,10 @@ class LIBPROTOBUF_EXPORT CodedInputStream {
   //   something unusual.
   void SetTotalBytesLimit(int total_bytes_limit, int warning_threshold);
 
+  // The Total Bytes Limit minus the Current Position, or -1 if there
+  // is no Total Bytes Limit.
+  int BytesUntilTotalBytesLimit() const;
+
   // Recursion Limit -------------------------------------------------
   // To prevent corrupt or malicious messages from causing stack overflows,
   // we must keep track of the depth of recursion when parsing embedded
@@ -466,7 +481,7 @@ class LIBPROTOBUF_EXPORT CodedInputStream {
   int overflow_bytes_;
 
   // LastTagWas() stuff.
-  uint32 last_tag_;         // result of last ReadTag().
+  uint32 last_tag_;         // result of last ReadTag() or ReadTagWithCutoff().
 
   // This is set true by ReadTag{Fallback/Slow}() if it is called when exactly
   // at EOF, or by ExpectAtEnd() when it returns true.  This happens when we
@@ -638,6 +653,9 @@ class LIBPROTOBUF_EXPORT CodedOutputStream {
 
   // Write raw bytes, copying them from the given buffer.
   void WriteRaw(const void* buffer, int size);
+  // Like WriteRaw()  but will try to write aliased data if aliasing is
+  // turned on.
+  void WriteRawMaybeAliased(const void* data, int size);
   // Like WriteRaw()  but writing directly to the target array.
   // This is _not_ inlined, as the compiler often optimizes memcpy into inline
   // copy loops. Since this gets called by every field with string or bytes
@@ -649,8 +667,21 @@ class LIBPROTOBUF_EXPORT CodedOutputStream {
   void WriteString(const string& str);
   // Like WriteString()  but writing directly to the target array.
   static uint8* WriteStringToArray(const string& str, uint8* target);
+  // Write the varint-encoded size of str followed by str.
+  static uint8* WriteStringWithSizeToArray(const string& str, uint8* target);
 
 
+  // Instructs the CodedOutputStream to allow the underlying
+  // ZeroCopyOutputStream to hold pointers to the original structure instead of
+  // copying, if it supports it (i.e. output->AllowsAliasing() is true).  If the
+  // underlying stream does not support aliasing, then enabling it has no
+  // affect.  For now, this only affects the behavior of
+  // WriteRawMaybeAliased().
+  //
+  // NOTE: It is caller's responsibility to ensure that the chunk of memory
+  // remains live until all of the data has been consumed from the stream.
+  void EnableAliasing(bool enabled);
+
   // Write a 32-bit little-endian integer.
   void WriteLittleEndian32(uint32 value);
   // Like WriteLittleEndian32()  but writing directly to the target array.
@@ -725,6 +756,7 @@ class LIBPROTOBUF_EXPORT CodedOutputStream {
   int buffer_size_;
   int total_bytes_;  // Sum of sizes of all buffers seen so far.
   bool had_error_;   // Whether an error occurred during output.
+  bool aliasing_enabled_;  // See EnableAliasing().
 
   // Advance the buffer by a given number of bytes.
   void Advance(int amount);
@@ -733,6 +765,10 @@ class LIBPROTOBUF_EXPORT CodedOutputStream {
   // Advance(buffer_size_).
   bool Refresh();
 
+  // Like WriteRaw() but may avoid copying if the underlying
+  // ZeroCopyOutputStream supports it.
+  void WriteAliasedRaw(const void* buffer, int size);
+
   static uint8* WriteVarint32FallbackToArray(uint32 value, uint8* target);
 
   // Always-inlined versions of WriteVarint* functions so that code can be
@@ -850,6 +886,45 @@ inline uint32 CodedInputStream::ReadTag() {
   }
 }
 
+inline std::pair<uint32, bool> CodedInputStream::ReadTagWithCutoff(
+    uint32 cutoff) {
+  // In performance-sensitive code we can expect cutoff to be a compile-time
+  // constant, and things like "cutoff >= kMax1ByteVarint" to be evaluated at
+  // compile time.
+  if (GOOGLE_PREDICT_TRUE(buffer_ < buffer_end_)) {
+    // Hot case: buffer_ non_empty, buffer_[0] in [1, 128).
+    // TODO(gpike): Is it worth rearranging this? E.g., if the number of fields
+    // is large enough then is it better to check for the two-byte case first?
+    if (static_cast<int8>(buffer_[0]) > 0) {
+      const uint32 kMax1ByteVarint = 0x7f;
+      uint32 tag = last_tag_ = buffer_[0];
+      Advance(1);
+      return make_pair(tag, cutoff >= kMax1ByteVarint || tag <= cutoff);
+    }
+    // Other hot case: cutoff >= 0x80, buffer_ has at least two bytes available,
+    // and tag is two bytes.  The latter is tested by bitwise-and-not of the
+    // first byte and the second byte.
+    if (cutoff >= 0x80 &&
+        GOOGLE_PREDICT_TRUE(buffer_ + 1 < buffer_end_) &&
+        GOOGLE_PREDICT_TRUE((buffer_[0] & ~buffer_[1]) >= 0x80)) {
+      const uint32 kMax2ByteVarint = (0x7f << 7) + 0x7f;
+      uint32 tag = last_tag_ = (1u << 7) * buffer_[1] + (buffer_[0] - 0x80);
+      Advance(2);
+      // It might make sense to test for tag == 0 now, but it is so rare that
+      // that we don't bother.  A varint-encoded 0 should be one byte unless
+      // the encoder lost its mind.  The second part of the return value of
+      // this function is allowed to be either true or false if the tag is 0,
+      // so we don't have to check for tag == 0.  We may need to check whether
+      // it exceeds cutoff.
+      bool at_or_below_cutoff = cutoff >= kMax2ByteVarint || tag <= cutoff;
+      return make_pair(tag, at_or_below_cutoff);
+    }
+  }
+  // Slow path
+  last_tag_ = ReadTagFallback();
+  return make_pair(last_tag_, static_cast<uint32>(last_tag_ - 1) < cutoff);
+}
+
 inline bool CodedInputStream::LastTagWas(uint32 expected) {
   return last_tag_ == expected;
 }
@@ -1029,6 +1104,15 @@ inline void CodedOutputStream::WriteString(const string& str) {
   WriteRaw(str.data(), static_cast<int>(str.size()));
 }
 
+inline void CodedOutputStream::WriteRawMaybeAliased(
+    const void* data, int size) {
+  if (aliasing_enabled_) {
+    WriteAliasedRaw(data, size);
+  } else {
+    WriteRaw(data, size);
+  }
+}
+
 inline uint8* CodedOutputStream::WriteStringToArray(
     const string& str, uint8* target) {
   return WriteRawToArray(str.data(), static_cast<int>(str.size()), target);