message.h

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// 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
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//
// 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,
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// 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.

// Author: [email protected] (Kenton Varda)
// Based on original Protocol Buffers design by
// Sanjay Ghemawat, Jeff Dean, and others.
//
// Defines Message, the abstract interface implemented by non-lite
// protocol message objects. 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;
// const Descriptor* descriptor = foo->GetDescriptor();
//
// // Get the descriptors for the fields we're interested in and verify
// // their types.
// const FieldDescriptor* text_field = descriptor->FindFieldByName("text");
// assert(text_field != NULL);
// assert(text_field->type() == FieldDescriptor::TYPE_STRING);
// assert(text_field->label() == FieldDescriptor::LABEL_OPTIONAL);
// const FieldDescriptor* numbers_field = descriptor->
// FindFieldByName("numbers");
// assert(numbers_field != NULL);
// assert(numbers_field->type() == FieldDescriptor::TYPE_INT32);
// assert(numbers_field->label() == FieldDescriptor::LABEL_REPEATED);
//
// // Parse the message.
// foo->ParseFromString(data);
//
// // Use the reflection interface to examine the contents.
// const Reflection* reflection = foo->GetReflection();
// assert(reflection->GetString(foo, text_field) == "Hello World!");
// assert(reflection->FieldSize(foo, numbers_field) == 3);
// assert(reflection->GetRepeatedInt32(foo, numbers_field, 0) == 1);
// assert(reflection->GetRepeatedInt32(foo, numbers_field, 1) == 5);
// assert(reflection->GetRepeatedInt32(foo, numbers_field, 2) == 42);
//
// delete foo;
// }

#ifndef GOOGLE_PROTOBUF_MESSAGE_H__
#define GOOGLE_PROTOBUF_MESSAGE_H__

#include <iosfwd>
#include <string>
#include <vector>

#include <google/protobuf/message_lite.h>

#include <google/protobuf/stubs/common.h>
#include <google/protobuf/descriptor.h>


#define GOOGLE_PROTOBUF_HAS_ONEOF

namespace google {
namespace protobuf {

// Defined in this file.
class Message;
class Reflection;
class MessageFactory;

// Defined in other files.
class UnknownFieldSet; // unknown_field_set.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
}


template<typename T>
class RepeatedField; // repeated_field.h

template<typename T>
class RepeatedPtrField; // repeated_field.h

// A container to hold message metadata.
struct Metadata {
 const Descriptor* descriptor;
 const Reflection* reflection;
};

// Abstract interface for protocol messages.
//
// See also MessageLite, which contains most every-day operations. Message
// adds descriptors and reflection on top of that.
//
// 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 MessageLite {
 public:
 inline Message() {}
 virtual ~Message();

 // Basic Operations ------------------------------------------------

 // Construct a new instance of the same type. Ownership is passed to the
 // caller. (This is also defined in MessageLite, but is defined again here
 // for return-type covariance.)
 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, if specified in from, 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);

 // 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();

 // Computes (an estimate of) the total number of bytes currently used for
 // storing the message in memory. The default implementation calls the
 // Reflection object's SpaceUsed() method.
 virtual int SpaceUsed() const;

 // Debugging & Testing----------------------------------------------

 // 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;
 // Like DebugString(), but do not escape UTF-8 byte sequences.
 string Utf8DebugString() const;
 // Convenience function useful in GDB. Prints DebugString() to stdout.
 void PrintDebugString() const;

 // Heavy I/O -------------------------------------------------------
 // Additional parsing and serialization methods not implemented by
 // MessageLite because they are not supported by the lite library.

 // 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);

 // 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;


 // Reflection-based methods ----------------------------------------
 // These methods are pure-virtual in MessageLite, but Message provides
 // reflection-based default implementations.

 virtual string GetTypeName() const;
 virtual void Clear();
 virtual bool IsInitialized() const;
 virtual void CheckTypeAndMergeFrom(const MessageLite& other);
 virtual bool MergePartialFromCodedStream(io::CodedInputStream* input);
 virtual int ByteSize() const;
 virtual void SerializeWithCachedSizes(io::CodedOutputStream* output) const;

 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 ---------------------------------------------------

 // Typedef for backwards-compatibility.
 typedef google::protobuf::Reflection Reflection;

 // Get a Descriptor for this message's type. This describes what
 // fields the message contains, the types of those fields, etc.
 const Descriptor* GetDescriptor() const { return GetMetadata().descriptor; }

 // 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.
 //
 // This method remains virtual in case a subclass does not implement
 // reflection and wants to override the default behavior.
 virtual const Reflection* GetReflection() const {
 return GetMetadata().reflection;
 }

 protected:
 // Get a struct containing the metadata for the Message. Most subclasses only
 // need to implement this method, rather than the GetDescriptor() and
 // GetReflection() wrappers.
 virtual Metadata GetMetadata() const = 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), and all Messages of a particular class
// should share the same Reflection object (though you should not rely on
// the latter fact).
//
// 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.
// - The Message object passed to any method is not of the right type for
// this Reflection object (i.e. message.GetReflection() != reflection).
//
// 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 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 Message& message) 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(Message* message) const = 0;

 // Estimate the amount of memory used by the message object.
 virtual int SpaceUsed(const Message& message) const = 0;

 // Check if the given non-repeated field is set.
 virtual bool HasField(const Message& message,
 const FieldDescriptor* field) const = 0;

 // Get the number of elements of a repeated field.
 virtual int FieldSize(const Message& message,
 const FieldDescriptor* field) const = 0;

 // Clear the value of a field, so that HasField() returns false or
 // FieldSize() returns zero.
 virtual void ClearField(Message* message,
 const FieldDescriptor* field) const = 0;

 // Check if the oneof is set. Returns ture if any field in oneof
 // is set, false otherwise.
 // TODO(jieluo) - make it pure virtual after updating all
 // the subclasses.
 virtual bool HasOneof(const Message& /*message*/,
 const OneofDescriptor* /*oneof_descriptor*/) const {
 return false;
 }

 virtual void ClearOneof(Message* /*message*/,
 const OneofDescriptor* /*oneof_descriptor*/) const {}

 // Returns the field descriptor if the oneof is set. NULL otherwise.
 // TODO(jieluo) - make it pure virtual.
 virtual const FieldDescriptor* GetOneofFieldDescriptor(
 const Message& /*message*/,
 const OneofDescriptor* /*oneof_descriptor*/) const {
 return NULL;
 }

 // Removes the last element of a repeated field.
 // We don't provide a way to remove any element other than the last
 // because it invites inefficient use, such as O(n^2) filtering loops
 // that should have been O(n). If you want to remove an element other
 // than the last, the best way to do it is to re-arrange the elements
 // (using Swap()) so that the one you want removed is at the end, then
 // call RemoveLast().
 virtual void RemoveLast(Message* message,
 const FieldDescriptor* field) const = 0;
 // Removes the last element of a repeated message field, and returns the
 // pointer to the caller. Caller takes ownership of the returned pointer.
 virtual Message* ReleaseLast(Message* message,
 const FieldDescriptor* field) const = 0;

 // Swap the complete contents of two messages.
 virtual void Swap(Message* message1, Message* message2) const = 0;

 // Swap fields listed in fields vector of two messages.
 virtual void SwapFields(Message* message1,
 Message* message2,
 const vector<const FieldDescriptor*>& fields)
 const = 0;

 // Swap two elements of a repeated field.
 virtual void SwapElements(Message* message,
 const FieldDescriptor* field,
 int index1,
 int index2) const = 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(const Message& message,
 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 Message& message,
 const FieldDescriptor* field) const = 0;
 virtual int64 GetInt64 (const Message& message,
 const FieldDescriptor* field) const = 0;
 virtual uint32 GetUInt32(const Message& message,
 const FieldDescriptor* field) const = 0;
 virtual uint64 GetUInt64(const Message& message,
 const FieldDescriptor* field) const = 0;
 virtual float GetFloat (const Message& message,
 const FieldDescriptor* field) const = 0;
 virtual double GetDouble(const Message& message,
 const FieldDescriptor* field) const = 0;
 virtual bool GetBool (const Message& message,
 const FieldDescriptor* field) const = 0;
 virtual string GetString(const Message& message,
 const FieldDescriptor* field) const = 0;
 virtual const EnumValueDescriptor* GetEnum(
 const Message& message, const FieldDescriptor* field) const = 0;
 // See MutableMessage() for the meaning of the "factory" parameter.
 virtual const Message& GetMessage(const Message& message,
 const FieldDescriptor* field,
 MessageFactory* factory = NULL) 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 Message& message,
 const FieldDescriptor* field,
 string* scratch) const = 0;


 // Singular field mutators -----------------------------------------
 // These mutate the value of a non-repeated field.

 virtual void SetInt32 (Message* message,
 const FieldDescriptor* field, int32 value) const = 0;
 virtual void SetInt64 (Message* message,
 const FieldDescriptor* field, int64 value) const = 0;
 virtual void SetUInt32(Message* message,
 const FieldDescriptor* field, uint32 value) const = 0;
 virtual void SetUInt64(Message* message,
 const FieldDescriptor* field, uint64 value) const = 0;
 virtual void SetFloat (Message* message,
 const FieldDescriptor* field, float value) const = 0;
 virtual void SetDouble(Message* message,
 const FieldDescriptor* field, double value) const = 0;
 virtual void SetBool (Message* message,
 const FieldDescriptor* field, bool value) const = 0;
 virtual void SetString(Message* message,
 const FieldDescriptor* field,
 const string& value) const = 0;
 virtual void SetEnum (Message* message,
 const FieldDescriptor* field,
 const EnumValueDescriptor* value) const = 0;
 // Get a mutable pointer to a field with a message type. If a MessageFactory
 // is provided, it will be used to construct instances of the sub-message;
 // otherwise, the default factory is used. If the field is an extension that
 // does not live in the same pool as the containing message's descriptor (e.g.
 // it lives in an overlay pool), then a MessageFactory must be provided.
 // If you have no idea what that meant, then you probably don't need to worry
 // about it (don't provide a MessageFactory). WARNING: If the
 // FieldDescriptor is for a compiled-in extension, then
 // factory->GetPrototype(field->message_type() MUST return an instance of the
 // compiled-in class for this type, NOT DynamicMessage.
 virtual Message* MutableMessage(Message* message,
 const FieldDescriptor* field,
 MessageFactory* factory = NULL) const = 0;
 // Replaces the message specified by 'field' with the already-allocated object
 // sub_message, passing ownership to the message. If the field contained a
 // message, that message is deleted. If sub_message is NULL, the field is
 // cleared.
 virtual void SetAllocatedMessage(Message* message,
 Message* sub_message,
 const FieldDescriptor* field) const = 0;
 // Releases the message specified by 'field' and returns the pointer,
 // ReleaseMessage() will return the message the message object if it exists.
 // Otherwise, it may or may not return NULL. In any case, if the return value
 // is non-NULL, the caller takes ownership of the pointer.
 // If the field existed (HasField() is true), then the returned pointer will
 // be the same as the pointer returned by MutableMessage().
 // This function has the same effect as ClearField().
 virtual Message* ReleaseMessage(Message* message,
 const FieldDescriptor* field,
 MessageFactory* factory = NULL) const = 0;


 // Repeated field getters ------------------------------------------
 // These get the value of one element of a repeated field.

 virtual int32 GetRepeatedInt32 (const Message& message,
 const FieldDescriptor* field,
 int index) const = 0;
 virtual int64 GetRepeatedInt64 (const Message& message,
 const FieldDescriptor* field,
 int index) const = 0;
 virtual uint32 GetRepeatedUInt32(const Message& message,
 const FieldDescriptor* field,
 int index) const = 0;
 virtual uint64 GetRepeatedUInt64(const Message& message,
 const FieldDescriptor* field,
 int index) const = 0;
 virtual float GetRepeatedFloat (const Message& message,
 const FieldDescriptor* field,
 int index) const = 0;
 virtual double GetRepeatedDouble(const Message& message,
 const FieldDescriptor* field,
 int index) const = 0;
 virtual bool GetRepeatedBool (const Message& message,
 const FieldDescriptor* field,
 int index) const = 0;
 virtual string GetRepeatedString(const Message& message,
 const FieldDescriptor* field,
 int index) const = 0;
 virtual const EnumValueDescriptor* GetRepeatedEnum(
 const Message& message,
 const FieldDescriptor* field, int index) const = 0;
 virtual const Message& GetRepeatedMessage(
 const Message& message,
 const FieldDescriptor* field, int index) const = 0;

 // See GetStringReference(), above.
 virtual const string& GetRepeatedStringReference(
 const Message& message, 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 (Message* message,
 const FieldDescriptor* field,
 int index, int32 value) const = 0;
 virtual void SetRepeatedInt64 (Message* message,
 const FieldDescriptor* field,
 int index, int64 value) const = 0;
 virtual void SetRepeatedUInt32(Message* message,
 const FieldDescriptor* field,
 int index, uint32 value) const = 0;
 virtual void SetRepeatedUInt64(Message* message,
 const FieldDescriptor* field,
 int index, uint64 value) const = 0;
 virtual void SetRepeatedFloat (Message* message,
 const FieldDescriptor* field,
 int index, float value) const = 0;
 virtual void SetRepeatedDouble(Message* message,
 const FieldDescriptor* field,
 int index, double value) const = 0;
 virtual void SetRepeatedBool (Message* message,
 const FieldDescriptor* field,
 int index, bool value) const = 0;
 virtual void SetRepeatedString(Message* message,
 const FieldDescriptor* field,
 int index, const string& value) const = 0;
 virtual void SetRepeatedEnum(Message* message,
 const FieldDescriptor* field, int index,
 const EnumValueDescriptor* value) const = 0;
 // Get a mutable pointer to an element of a repeated field with a message
 // type.
 virtual Message* MutableRepeatedMessage(
 Message* message, const FieldDescriptor* field, int index) const = 0;


 // Repeated field adders -------------------------------------------
 // These add an element to a repeated field.

 virtual void AddInt32 (Message* message,
 const FieldDescriptor* field, int32 value) const = 0;
 virtual void AddInt64 (Message* message,
 const FieldDescriptor* field, int64 value) const = 0;
 virtual void AddUInt32(Message* message,
 const FieldDescriptor* field, uint32 value) const = 0;
 virtual void AddUInt64(Message* message,
 const FieldDescriptor* field, uint64 value) const = 0;
 virtual void AddFloat (Message* message,
 const FieldDescriptor* field, float value) const = 0;
 virtual void AddDouble(Message* message,
 const FieldDescriptor* field, double value) const = 0;
 virtual void AddBool (Message* message,
 const FieldDescriptor* field, bool value) const = 0;
 virtual void AddString(Message* message,
 const FieldDescriptor* field,
 const string& value) const = 0;
 virtual void AddEnum (Message* message,
 const FieldDescriptor* field,
 const EnumValueDescriptor* value) const = 0;
 // See MutableMessage() for comments on the "factory" parameter.
 virtual Message* AddMessage(Message* message,
 const FieldDescriptor* field,
 MessageFactory* factory = NULL) const = 0;


 // Repeated field accessors -------------------------------------------------
 // The methods above, e.g. GetRepeatedInt32(msg, fd, index), provide singular
 // access to the data in a RepeatedField. The methods below provide aggregate
 // access by exposing the RepeatedField object itself with the Message.
 // Applying these templates to inappropriate types will lead to an undefined
 // reference at link time (e.g. GetRepeatedField<***double>), or possibly a
 // template matching error at compile time (e.g. GetRepeatedPtrField<File>).
 //
 // Usage example: my_doubs = refl->GetRepeatedField<double>(msg, fd);

 // for T = Cord and all protobuf scalar types except enums.
 template<typename T>
 const RepeatedField<T>& GetRepeatedField(
 const Message&, const FieldDescriptor*) const;

 // for T = Cord and all protobuf scalar types except enums.
 template<typename T>
 RepeatedField<T>* MutableRepeatedField(
 Message*, const FieldDescriptor*) const;

 // for T = string, google::protobuf::internal::StringPieceField
 // google::protobuf::Message & descendants.
 template<typename T>
 const RepeatedPtrField<T>& GetRepeatedPtrField(
 const Message&, const FieldDescriptor*) const;

 // for T = string, google::protobuf::internal::StringPieceField
 // google::protobuf::Message & descendants.
 template<typename T>
 RepeatedPtrField<T>* MutableRepeatedPtrField(
 Message*, const FieldDescriptor*) const;

 // 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;

 // ---------------------------------------------------------------------------

 protected:
 // Obtain a pointer to a Repeated Field Structure and do some type checking:
 // on field->cpp_type(),
 // on field->field_option().ctype() (if ctype >= 0)
 // of field->message_type() (if message_type != NULL).
 // We use 1 routine rather than 4 (const vs mutable) x (scalar vs pointer).
 virtual void* MutableRawRepeatedField(
 Message* message, const FieldDescriptor* field, FieldDescriptor::CppType,
 int ctype, const Descriptor* message_type) const = 0;

 private:
 // Special version for specialized implementations of string. We can't call
 // MutableRawRepeatedField directly here because we don't have access to
 // FieldOptions::* which are defined in descriptor.pb.h. Including that
 // file here is not possible because it would cause a circular include cycle.
 void* MutableRawRepeatedString(
 Message* message, const FieldDescriptor* field, bool is_string) const;

 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 destroyed 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 .proto file at static initialization
 // time, to be placed in generated_factory. The first time GetPrototype()
 // is called with a descriptor from this file, |register_messages| will be
 // called, with the file name as the parameter. It must call
 // InternalRegisterGeneratedMessage() (below) to register each message type
 // in the file. This strange mechanism is necessary because descriptors are
 // built lazily, so we can't register types by their descriptor until we
 // know that the descriptor exists. |filename| must be a permanent string.
 static void InternalRegisterGeneratedFile(
 const char* filename, void (*register_messages)(const string&));

 // For internal use only: Registers a message type. Called only by the
 // functions which are registered with InternalRegisterGeneratedFile(),
 // above.
 static void InternalRegisterGeneratedMessage(const Descriptor* descriptor,
 const Message* prototype);


 private:
 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MessageFactory);
};

#define DECLARE_GET_REPEATED_FIELD(TYPE) \
template<> \
LIBPROTOBUF_EXPORT \
const RepeatedField<TYPE>& Reflection::GetRepeatedField<TYPE>( \
 const Message& message, const FieldDescriptor* field) const; \
 \
template<> \
RepeatedField<TYPE>* Reflection::MutableRepeatedField<TYPE>( \
 Message* message, const FieldDescriptor* field) const;

DECLARE_GET_REPEATED_FIELD(int32)
DECLARE_GET_REPEATED_FIELD(int64)
DECLARE_GET_REPEATED_FIELD(uint32)
DECLARE_GET_REPEATED_FIELD(uint64)
DECLARE_GET_REPEATED_FIELD(float)
DECLARE_GET_REPEATED_FIELD(double)
DECLARE_GET_REPEATED_FIELD(bool)

#undef DECLARE_GET_REPEATED_FIELD

// =============================================================================
// Implementation details for {Get,Mutable}RawRepeatedPtrField. We provide
// specializations for <string>, <StringPieceField> and <Message> and handle
// everything else with the default template which will match any type having
// a method with signature "static const google::protobuf::Descriptor* descriptor()".
// Such a type presumably is a descendant of google::protobuf::Message.

template<>
inline const RepeatedPtrField<string>& Reflection::GetRepeatedPtrField<string>(
 const Message& message, const FieldDescriptor* field) const {
 return *static_cast<RepeatedPtrField<string>* >(
 MutableRawRepeatedString(const_cast<Message*>(&message), field, true));
}

template<>
inline RepeatedPtrField<string>* Reflection::MutableRepeatedPtrField<string>(
 Message* message, const FieldDescriptor* field) const {
 return static_cast<RepeatedPtrField<string>* >(
 MutableRawRepeatedString(message, field, true));
}


// -----

template<>
inline const RepeatedPtrField<Message>& Reflection::GetRepeatedPtrField(
 const Message& message, const FieldDescriptor* field) const {
 return *static_cast<RepeatedPtrField<Message>* >(
 MutableRawRepeatedField(const_cast<Message*>(&message), field,
 FieldDescriptor::CPPTYPE_MESSAGE, -1,
 NULL));
}

template<>
inline RepeatedPtrField<Message>* Reflection::MutableRepeatedPtrField(
 Message* message, const FieldDescriptor* field) const {
 return static_cast<RepeatedPtrField<Message>* >(
 MutableRawRepeatedField(message, field,
 FieldDescriptor::CPPTYPE_MESSAGE, -1,
 NULL));
}

template<typename PB>
inline const RepeatedPtrField<PB>& Reflection::GetRepeatedPtrField(
 const Message& message, const FieldDescriptor* field) const {
 return *static_cast<RepeatedPtrField<PB>* >(
 MutableRawRepeatedField(const_cast<Message*>(&message), field,
 FieldDescriptor::CPPTYPE_MESSAGE, -1,
 PB::default_instance().GetDescriptor()));
}

template<typename PB>
inline RepeatedPtrField<PB>* Reflection::MutableRepeatedPtrField(
 Message* message, const FieldDescriptor* field) const {
 return static_cast<RepeatedPtrField<PB>* >(
 MutableRawRepeatedField(message, field,
 FieldDescriptor::CPPTYPE_MESSAGE, -1,
 PB::default_instance().GetDescriptor()));
}

} // namespace protobuf

} // namespace google
#endif // GOOGLE_PROTOBUF_MESSAGE_H__