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+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.
+// http://code.google.com/p/protobuf/
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Author: kenton@google.com (Kenton Varda)
+//  Based on original Protocol Buffers design by
+//  Sanjay Ghemawat, Jeff Dean, and others.
+//
+// This file contains the abstract interface for all protocol messages.
+// Although it's possible to implement this interface manually, most users
+// will use the protocol compiler to generate implementations.
+//
+// Example usage:
+//
+// Say you have a message defined as:
+//
+//   message Foo {
+//     optional string text = 1;
+//     repeated int32 numbers = 2;
+//   }
+//
+// Then, if you used the protocol compiler to generate a class from the above
+// definition, you could use it like so:
+//
+//   string data;  // Will store a serialized version of the message.
+//
+//   {
+//     // Create a message and serialize it.
+//     Foo foo;
+//     foo.set_text("Hello World!");
+//     foo.add_numbers(1);
+//     foo.add_numbers(5);
+//     foo.add_numbers(42);
+//
+//     foo.SerializeToString(&data);
+//   }
+//
+//   {
+//     // Parse the serialized message and check that it contains the
+//     // correct data.
+//     Foo foo;
+//     foo.ParseFromString(data);
+//
+//     assert(foo.text() == "Hello World!");
+//     assert(foo.numbers_size() == 3);
+//     assert(foo.numbers(0) == 1);
+//     assert(foo.numbers(1) == 5);
+//     assert(foo.numbers(2) == 42);
+//   }
+//
+//   {
+//     // Same as the last block, but do it dynamically via the Message
+//     // reflection interface.
+//     Message* foo = new Foo;
+//     Descriptor* descriptor = foo->GetDescriptor();
+//
+//     // Get the descriptors for the fields we're interested in and verify
+//     // their types.
+//     FieldDescriptor* text_field = descriptor->FindFieldByName("text");
+//     assert(text_field != NULL);
+//     assert(text_field->type() == FieldDescriptor::TYPE_STRING);
+//     assert(text_field->label() == FieldDescriptor::TYPE_OPTIONAL);
+//     FieldDescriptor* numbers_field = descriptor->FindFieldByName("numbers");
+//     assert(numbers_field != NULL);
+//     assert(numbers_field->type() == FieldDescriptor::TYPE_INT32);
+//     assert(numbers_field->label() == FieldDescriptor::TYPE_REPEATED);
+//
+//     // Parse the message.
+//     foo->ParseFromString(data);
+//
+//     // Use the reflection interface to examine the contents.
+//     Message::Reflection* reflection = foo->GetReflection();
+//     assert(reflection->GetString(text_field) == "Hello World!");
+//     assert(reflection->CountField(numbers_field) == 3);
+//     assert(reflection->GetInt32(numbers_field, 0) == 1);
+//     assert(reflection->GetInt32(numbers_field, 1) == 5);
+//     assert(reflection->GetInt32(numbers_field, 2) == 42);
+//
+//     delete foo;
+//   }
+
+#ifndef GOOGLE_PROTOBUF_MESSAGE_H__
+#define GOOGLE_PROTOBUF_MESSAGE_H__
+
+#include <vector>
+#include <string>
+#include <iosfwd>
+#include <google/protobuf/stubs/common.h>
+
+namespace google {
+
+namespace protobuf {
+
+// Defined in this file.
+class Message;
+
+// Defined in other files.
+class Descriptor;            // descriptor.h
+class FieldDescriptor;       // descriptor.h
+class EnumValueDescriptor;   // descriptor.h
+namespace io {
+  class ZeroCopyInputStream;   // zero_copy_stream.h
+  class ZeroCopyOutputStream;  // zero_copy_stream.h
+  class CodedInputStream;      // coded_stream.h
+  class CodedOutputStream;     // coded_stream.h
+}
+class UnknownFieldSet;       // unknown_field_set.h
+
+// Abstract interface for protocol messages.
+//
+// The methods of this class that are virtual but not pure-virtual have
+// default implementations based on reflection.  Message classes which are
+// optimized for speed will want to override these with faster implementations,
+// but classes optimized for code size may be happy with keeping them.  See
+// the optimize_for option in descriptor.proto.
+class LIBPROTOBUF_EXPORT Message {
+ public:
+  inline Message() {}
+  virtual ~Message();
+
+  // Basic Operations ------------------------------------------------
+
+  // Construct a new instance of the same type.  Ownership is passed to the
+  // caller.
+  virtual Message* New() const = 0;
+
+  // Make this message into a copy of the given message.  The given message
+  // must have the same descriptor, but need not necessarily be the same class.
+  // By default this is just implemented as "Clear(); MergeFrom(from);".
+  virtual void CopyFrom(const Message& from);
+
+  // Merge the fields from the given message into this message.  Singular
+  // fields will be overwritten, except for embedded messages which will
+  // be merged.  Repeated fields will be concatenated.  The given message
+  // must be of the same type as this message (i.e. the exact same class).
+  virtual void MergeFrom(const Message& from);
+
+  // Clear all fields of the message and set them to their default values.
+  // Clear() avoids freeing memory, assuming that any memory allocated
+  // to hold parts of the message will be needed again to hold the next
+  // message.  If you actually want to free the memory used by a Message,
+  // you must delete it.
+  virtual void Clear();
+
+  // Quickly check if all required fields have values set.
+  virtual bool IsInitialized() const;
+
+  // Verifies that IsInitialized() returns true.  GOOGLE_CHECK-fails otherwise, with
+  // a nice error message.
+  void CheckInitialized() const;
+
+  // Slowly build a list of all required fields that are not set.
+  // This is much, much slower than IsInitialized() as it is implemented
+  // purely via reflection.  Generally, you should not call this unless you
+  // have already determined that an error exists by calling IsInitialized().
+  void FindInitializationErrors(vector<string>* errors) const;
+
+  // Like FindInitializationErrors, but joins all the strings, delimited by
+  // commas, and returns them.
+  string InitializationErrorString() const;
+
+  // Clears all unknown fields from this message and all embedded messages.
+  // Normally, if unknown tag numbers are encountered when parsing a message,
+  // the tag and value are stored in the message's UnknownFieldSet and
+  // then written back out when the message is serialized.  This allows servers
+  // which simply route messages to other servers to pass through messages
+  // that have new field definitions which they don't yet know about.  However,
+  // this behavior can have security implications.  To avoid it, call this
+  // method after parsing.
+  //
+  // See Reflection::GetUnknownFields() for more on unknown fields.
+  virtual void DiscardUnknownFields();
+
+  // Debugging -------------------------------------------------------
+
+  // Generates a human readable form of this message, useful for debugging
+  // and other purposes.
+  string DebugString() const;
+  // Like DebugString(), but with less whitespace.
+  string ShortDebugString() const;
+  // Convenience function useful in GDB.  Prints DebugString() to stdout.
+  void PrintDebugString() const;
+
+  // Parsing ---------------------------------------------------------
+  // Methods for parsing in protocol buffer format.  Most of these are
+  // just simple wrappers around MergeFromCodedStream().
+
+  // Fill the message with a protocol buffer parsed from the given input
+  // stream.  Returns false on a read error or if the input is in the
+  // wrong format.
+  bool ParseFromCodedStream(io::CodedInputStream* input);
+  // Like ParseFromCodedStream(), but accepts messages that are missing
+  // required fields.
+  bool ParsePartialFromCodedStream(io::CodedInputStream* input);
+  // Read a protocol buffer from the given zero-copy input stream.  If
+  // successful, the entire input will be consumed.
+  bool ParseFromZeroCopyStream(io::ZeroCopyInputStream* input);
+  // Like ParseFromZeroCopyStream(), but accepts messages that are missing
+  // required fields.
+  bool ParsePartialFromZeroCopyStream(io::ZeroCopyInputStream* input);
+  // Parse a protocol buffer contained in a string.
+  bool ParseFromString(const string& data);
+  // Like ParseFromString(), but accepts messages that are missing
+  // required fields.
+  bool ParsePartialFromString(const string& data);
+  // Parse a protocol buffer contained in an array of bytes.
+  bool ParseFromArray(const void* data, int size);
+  // Like ParseFromArray(), but accepts messages that are missing
+  // required fields.
+  bool ParsePartialFromArray(const void* data, int size);
+
+  // Parse a protocol buffer from a file descriptor.  If successful, the entire
+  // input will be consumed.
+  bool ParseFromFileDescriptor(int file_descriptor);
+  // Like ParseFromFileDescriptor(), but accepts messages that are missing
+  // required fields.
+  bool ParsePartialFromFileDescriptor(int file_descriptor);
+  // Parse a protocol buffer from a C++ istream.  If successful, the entire
+  // input will be consumed.
+  bool ParseFromIstream(istream* input);
+  // Like ParseFromIstream(), but accepts messages that are missing
+  // required fields.
+  bool ParsePartialFromIstream(istream* input);
+
+
+  // Reads a protocol buffer from the stream and merges it into this
+  // Message.  Singular fields read from the input overwrite what is
+  // already in the Message and repeated fields are appended to those
+  // already present.
+  //
+  // It is the responsibility of the caller to call input->LastTagWas()
+  // (for groups) or input->ConsumedEntireMessage() (for non-groups) after
+  // this returns to verify that the message's end was delimited correctly.
+  //
+  // ParsefromCodedStream() is implemented as Clear() followed by
+  // MergeFromCodedStream().
+  bool MergeFromCodedStream(io::CodedInputStream* input);
+
+  // Like MergeFromCodedStream(), but succeeds even if required fields are
+  // missing in the input.
+  //
+  // MergeFromCodedStream() is just implemented as MergePartialFromCodedStream()
+  // followed by IsInitialized().
+  virtual bool MergePartialFromCodedStream(io::CodedInputStream* input);
+
+  // Serialization ---------------------------------------------------
+  // Methods for serializing in protocol buffer format.  Most of these
+  // are just simple wrappers around ByteSize() and SerializeWithCachedSizes().
+
+  // Write a protocol buffer of this message to the given output.  Returns
+  // false on a write error.  If the message is missing required fields,
+  // this may GOOGLE_CHECK-fail.
+  bool SerializeToCodedStream(io::CodedOutputStream* output) const;
+  // Like SerializeToCodedStream(), but allows missing required fields.
+  bool SerializePartialToCodedStream(io::CodedOutputStream* output) const;
+  // Write the message to the given zero-copy output stream.  All required
+  // fields must be set.
+  bool SerializeToZeroCopyStream(io::ZeroCopyOutputStream* output) const;
+  // Like SerializeToZeroCopyStream(), but allows missing required fields.
+  bool SerializePartialToZeroCopyStream(io::ZeroCopyOutputStream* output) const;
+  // Serialize the message and store it in the given string.  All required
+  // fields must be set.
+  bool SerializeToString(string* output) const;
+  // Like SerializeToString(), but allows missing required fields.
+  bool SerializePartialToString(string* output) const;
+  // Serialize the message and store it in the given byte array.  All required
+  // fields must be set.
+  bool SerializeToArray(void* data, int size) const;
+  // Like SerializeToArray(), but allows missing required fields.
+  bool SerializePartialToArray(void* data, int size) const;
+
+  // Serialize the message and write it to the given file descriptor.  All
+  // required fields must be set.
+  bool SerializeToFileDescriptor(int file_descriptor) const;
+  // Like SerializeToFileDescriptor(), but allows missing required fields.
+  bool SerializePartialToFileDescriptor(int file_descriptor) const;
+  // Serialize the message and write it to the given C++ ostream.  All
+  // required fields must be set.
+  bool SerializeToOstream(ostream* output) const;
+  // Like SerializeToOstream(), but allows missing required fields.
+  bool SerializePartialToOstream(ostream* output) const;
+
+
+  // Like SerializeToString(), but appends to the data to the string's existing
+  // contents.  All required fields must be set.
+  bool AppendToString(string* output) const;
+  // Like AppendToString(), but allows missing required fields.
+  bool AppendPartialToString(string* output) const;
+
+  // Computes the serialized size of the message.  This recursively calls
+  // ByteSize() on all embedded messages.  If a subclass does not override
+  // this, it MUST override SetCachedSize().
+  virtual int ByteSize() const;
+
+  // Serializes the message without recomputing the size.  The message must
+  // not have changed since the last call to ByteSize(); if it has, the results
+  // are undefined.
+  virtual bool SerializeWithCachedSizes(io::CodedOutputStream* output) const;
+
+  // Returns the result of the last call to ByteSize().  An embedded message's
+  // size is needed both to serialize it (because embedded messages are
+  // length-delimited) and to compute the outer message's size.  Caching
+  // the size avoids computing it multiple times.
+  //
+  // ByteSize() does not automatically use the cached size when available
+  // because this would require invalidating it every time the message was
+  // modified, which would be too hard and expensive.  (E.g. if a deeply-nested
+  // sub-message is changed, all of its parents' cached sizes would need to be
+  // invalidated, which is too much work for an otherwise inlined setter
+  // method.)
+  virtual int GetCachedSize() const = 0;
+
+ private:
+  // This is called only by the default implementation of ByteSize(), to
+  // update the cached size.  If you override ByteSize(), you do not need
+  // to override this.  If you do not override ByteSize(), you MUST override
+  // this; the default implementation will crash.
+  //
+  // The method is private because subclasses should never call it; only
+  // override it.  Yes, C++ lets you do that.  Crazy, huh?
+  virtual void SetCachedSize(int size) const;
+
+ public:
+
+  // Introspection ---------------------------------------------------
+
+  class Reflection;  // Defined below.
+
+  // Get a Descriptor for this message's type.  This describes what
+  // fields the message contains, the types of those fields, etc.
+  virtual const Descriptor* GetDescriptor() const = 0;
+
+  // Get the Reflection interface for this Message, which can be used to
+  // read and modify the fields of the Message dynamically (in other words,
+  // without knowing the message type at compile time).  This object remains
+  // property of the Message.
+  virtual const Reflection* GetReflection() const = 0;
+
+  // Get the Reflection interface for this Message, which can be used to
+  // read and modify the fields of the Message dynamically (in other words,
+  // without knowing the message type at compile time).  This object remains
+  // property of the Message.
+  virtual Reflection* GetReflection() = 0;
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(Message);
+};
+
+// This interface contains methods that can be used to dynamically access
+// and modify the fields of a protocol message.  Their semantics are
+// similar to the accessors the protocol compiler generates.
+//
+// To get the Reflection for a given Message, call Message::GetReflection().
+//
+// This interface is separate from Message only for efficiency reasons;
+// the vast majority of implementations of Message will share the same
+// implementation of Reflection (GeneratedMessageReflection,
+// defined in generated_message.h).
+//
+// There are several ways that these methods can be used incorrectly.  For
+// example, any of the following conditions will lead to undefined
+// results (probably assertion failures):
+// - The FieldDescriptor is not a field of this message type.
+// - The method called is not appropriate for the field's type.  For
+//   each field type in FieldDescriptor::TYPE_*, there is only one
+//   Get*() method, one Set*() method, and one Add*() method that is
+//   valid for that type.  It should be obvious which (except maybe
+//   for TYPE_BYTES, which are represented using strings in C++).
+// - A Get*() or Set*() method for singular fields is called on a repeated
+//   field.
+// - GetRepeated*(), SetRepeated*(), or Add*() is called on a non-repeated
+//   field.
+//
+// You might wonder why there is not any abstract representation for a field
+// of arbitrary type.  E.g., why isn't there just a "GetField()" method that
+// returns "const Field&", where "Field" is some class with accessors like
+// "GetInt32Value()".  The problem is that someone would have to deal with
+// allocating these Field objects.  For generated message classes, having to
+// allocate space for an additional object to wrap every field would at least
+// double the message's memory footprint, probably worse.  Allocating the
+// objects on-demand, on the other hand, would be expensive and prone to
+// memory leaks.  So, instead we ended up with this flat interface.
+//
+// TODO(kenton):  Create a utility class which callers can use to read and
+//   write fields from a Reflection without paying attention to the type.
+class LIBPROTOBUF_EXPORT Message::Reflection {
+ public:
+  inline Reflection() {}
+  virtual ~Reflection();
+
+  // Get the UnknownFieldSet for the message.  This contains fields which
+  // were seen when the Message was parsed but were not recognized according
+  // to the Message's definition.
+  virtual const UnknownFieldSet& GetUnknownFields() const = 0;
+  // Get a mutable pointer to the UnknownFieldSet for the message.  This
+  // contains fields which were seen when the Message was parsed but were not
+  // recognized according to the Message's definition.
+  virtual UnknownFieldSet* MutableUnknownFields() = 0;
+
+  // Check if the given non-repeated field is set.
+  virtual bool HasField(const FieldDescriptor* field) const = 0;
+
+  // Get the number of elements of a repeated field.
+  virtual int FieldSize(const FieldDescriptor* field) const = 0;
+
+  // Clear the value of a field, so that HasField() returns false or
+  // FieldSize() returns zero.
+  virtual void ClearField(const FieldDescriptor* field) = 0;
+
+  // List all fields of the message which are currently set.  This includes
+  // extensions.  Singular fields will only be listed if HasField(field) would
+  // return true and repeated fields will only be listed if FieldSize(field)
+  // would return non-zero.  Fields (both normal fields and extension fields)
+  // will be listed ordered by field number.
+  virtual void ListFields(vector<const FieldDescriptor*>* output) const = 0;
+
+  // Singular field getters ------------------------------------------
+  // These get the value of a non-repeated field.  They return the default
+  // value for fields that aren't set.
+
+  virtual int32  GetInt32 (const FieldDescriptor* field) const = 0;
+  virtual int64  GetInt64 (const FieldDescriptor* field) const = 0;
+  virtual uint32 GetUInt32(const FieldDescriptor* field) const = 0;
+  virtual uint64 GetUInt64(const FieldDescriptor* field) const = 0;
+  virtual float  GetFloat (const FieldDescriptor* field) const = 0;
+  virtual double GetDouble(const FieldDescriptor* field) const = 0;
+  virtual bool   GetBool  (const FieldDescriptor* field) const = 0;
+  virtual string GetString(const FieldDescriptor* field) const = 0;
+  virtual const EnumValueDescriptor* GetEnum(
+      const FieldDescriptor* field) const = 0;
+  virtual const Message& GetMessage(const FieldDescriptor* field) const = 0;
+
+  // Get a string value without copying, if possible.
+  //
+  // GetString() necessarily returns a copy of the string.  This can be
+  // inefficient when the string is already stored in a string object in the
+  // underlying message.  GetStringReference() will return a reference to the
+  // underlying string in this case.  Otherwise, it will copy the string into
+  // *scratch and return that.
+  //
+  // Note:  It is perfectly reasonable and useful to write code like:
+  //     str = reflection->GetStringReference(field, &str);
+  //   This line would ensure that only one copy of the string is made
+  //   regardless of the field's underlying representation.  When initializing
+  //   a newly-constructed string, though, it's just as fast and more readable
+  //   to use code like:
+  //     string str = reflection->GetString(field);
+  virtual const string& GetStringReference(const FieldDescriptor* field,
+                                           string* scratch) const = 0;
+
+
+  // Singular field mutators -----------------------------------------
+  // These mutate the value of a non-repeated field.
+
+  virtual void SetInt32 (const FieldDescriptor* field, int32  value) = 0;
+  virtual void SetInt64 (const FieldDescriptor* field, int64  value) = 0;
+  virtual void SetUInt32(const FieldDescriptor* field, uint32 value) = 0;
+  virtual void SetUInt64(const FieldDescriptor* field, uint64 value) = 0;
+  virtual void SetFloat (const FieldDescriptor* field, float  value) = 0;
+  virtual void SetDouble(const FieldDescriptor* field, double value) = 0;
+  virtual void SetBool  (const FieldDescriptor* field, bool   value) = 0;
+  virtual void SetString(const FieldDescriptor* field, const string& value) = 0;
+  virtual void SetEnum  (const FieldDescriptor* field,
+                         const EnumValueDescriptor* value) = 0;
+  // Get a mutable pointer to a field with a message type.
+  virtual Message* MutableMessage(const FieldDescriptor* field) = 0;
+
+
+  // Repeated field getters ------------------------------------------
+  // These get the value of one element of a repeated field.
+
+  virtual int32  GetRepeatedInt32 (const FieldDescriptor* field,
+                                   int index) const = 0;
+  virtual int64  GetRepeatedInt64 (const FieldDescriptor* field,
+                                   int index) const = 0;
+  virtual uint32 GetRepeatedUInt32(const FieldDescriptor* field,
+                                   int index) const = 0;
+  virtual uint64 GetRepeatedUInt64(const FieldDescriptor* field,
+                                   int index) const = 0;
+  virtual float  GetRepeatedFloat (const FieldDescriptor* field,
+                                   int index) const = 0;
+  virtual double GetRepeatedDouble(const FieldDescriptor* field,
+                                   int index) const = 0;
+  virtual bool   GetRepeatedBool  (const FieldDescriptor* field,
+                                   int index) const = 0;
+  virtual string GetRepeatedString(const FieldDescriptor* field,
+                                   int index) const = 0;
+  virtual const EnumValueDescriptor* GetRepeatedEnum(
+      const FieldDescriptor* field, int index) const = 0;
+  virtual const Message& GetRepeatedMessage(
+      const FieldDescriptor* field, int index) const = 0;
+
+  // See GetStringReference(), above.
+  virtual const string& GetRepeatedStringReference(
+      const FieldDescriptor* field, int index,
+      string* scratch) const = 0;
+
+
+  // Repeated field mutators -----------------------------------------
+  // These mutate the value of one element of a repeated field.
+
+  virtual void SetRepeatedInt32 (const FieldDescriptor* field,
+                                 int index, int32  value) = 0;
+  virtual void SetRepeatedInt64 (const FieldDescriptor* field,
+                                 int index, int64  value) = 0;
+  virtual void SetRepeatedUInt32(const FieldDescriptor* field,
+                                 int index, uint32 value) = 0;
+  virtual void SetRepeatedUInt64(const FieldDescriptor* field,
+                                 int index, uint64 value) = 0;
+  virtual void SetRepeatedFloat (const FieldDescriptor* field,
+                                 int index, float  value) = 0;
+  virtual void SetRepeatedDouble(const FieldDescriptor* field,
+                                 int index, double value) = 0;
+  virtual void SetRepeatedBool  (const FieldDescriptor* field,
+                                 int index, bool   value) = 0;
+  virtual void SetRepeatedString(const FieldDescriptor* field,
+                                 int index, const string& value) = 0;
+  virtual void SetRepeatedEnum(const FieldDescriptor* field,
+                               int index, const EnumValueDescriptor* value) = 0;
+  // Get a mutable pointer to an element of a repeated field with a message
+  // type.
+  virtual Message* MutableRepeatedMessage(
+      const FieldDescriptor* field, int index) = 0;
+
+
+  // Repeated field adders -------------------------------------------
+  // These add an element to a repeated field.
+
+  virtual void AddInt32 (const FieldDescriptor* field, int32  value) = 0;
+  virtual void AddInt64 (const FieldDescriptor* field, int64  value) = 0;
+  virtual void AddUInt32(const FieldDescriptor* field, uint32 value) = 0;
+  virtual void AddUInt64(const FieldDescriptor* field, uint64 value) = 0;
+  virtual void AddFloat (const FieldDescriptor* field, float  value) = 0;
+  virtual void AddDouble(const FieldDescriptor* field, double value) = 0;
+  virtual void AddBool  (const FieldDescriptor* field, bool   value) = 0;
+  virtual void AddString(const FieldDescriptor* field, const string& value) = 0;
+  virtual void AddEnum  (const FieldDescriptor* field,
+                         const EnumValueDescriptor* value) = 0;
+  virtual Message* AddMessage(const FieldDescriptor* field) = 0;
+
+
+  // Extensions ------------------------------------------------------
+
+  // Try to find an extension of this message type by fully-qualified field
+  // name.  Returns NULL if no extension is known for this name or number.
+  virtual const FieldDescriptor* FindKnownExtensionByName(
+      const string& name) const = 0;
+
+  // Try to find an extension of this message type by field number.
+  // Returns NULL if no extension is known for this name or number.
+  virtual const FieldDescriptor* FindKnownExtensionByNumber(
+      int number) const = 0;
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(Reflection);
+};
+
+// Abstract interface for a factory for message objects.
+class LIBPROTOBUF_EXPORT MessageFactory {
+ public:
+  inline MessageFactory() {}
+  virtual ~MessageFactory();
+
+  // Given a Descriptor, gets or constructs the default (prototype) Message
+  // of that type.  You can then call that message's New() method to construct
+  // a mutable message of that type.
+  //
+  // Calling this method twice with the same Descriptor returns the same
+  // object.  The returned object remains property of the factory.  Also, any
+  // objects created by calling the prototype's New() method share some data
+  // with the prototype, so these must be destoyed before the MessageFactory
+  // is destroyed.
+  //
+  // The given descriptor must outlive the returned message, and hence must
+  // outlive the MessageFactory.
+  //
+  // Some implementations do not support all types.  GetPrototype() will
+  // return NULL if the descriptor passed in is not supported.
+  //
+  // This method may or may not be thread-safe depending on the implementation.
+  // Each implementation should document its own degree thread-safety.
+  virtual const Message* GetPrototype(const Descriptor* type) = 0;
+
+  // Gets a MessageFactory which supports all generated, compiled-in messages.
+  // In other words, for any compiled-in type FooMessage, the following is true:
+  //   MessageFactory::generated_factory()->GetPrototype(
+  //     FooMessage::descriptor()) == FooMessage::default_instance()
+  // This factory supports all types which are found in
+  // DescriptorPool::generated_pool().  If given a descriptor from any other
+  // pool, GetPrototype() will return NULL.  (You can also check if a
+  // descriptor is for a generated message by checking if
+  // descriptor->file()->pool() == DescriptorPool::generated_pool().)
+  //
+  // This factory is 100% thread-safe; calling GetPrototype() does not modify
+  // any shared data.
+  //
+  // This factory is a singleton.  The caller must not delete the object.
+  static MessageFactory* generated_factory();
+
+  // For internal use only:  Registers a message type at static initialization
+  // time, to be placed in generated_factory().
+  static void InternalRegisterGeneratedMessage(const Descriptor* descriptor,
+                                               const Message* prototype);
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MessageFactory);
+};
+
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_MESSAGE_H__