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// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc. All rights reserved.
// http://code.google.com/p/protobuf/
//
// 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.
// Author: kenton@google.com (Kenton Varda)
// Based on original Protocol Buffers design by
// Sanjay Ghemawat, Jeff Dean, and others.
//
// Defines an implementation of Message which can emulate types which are not
// known at compile-time.
#ifndef GOOGLE_PROTOBUF_DYNAMIC_MESSAGE_H__
#define GOOGLE_PROTOBUF_DYNAMIC_MESSAGE_H__
#include <google/protobuf/message.h>
#include <google/protobuf/stubs/common.h>
namespace google {
namespace protobuf {
// Defined in other files.
class Descriptor; // descriptor.h
class DescriptorPool; // descriptor.h
// Constructs implementations of Message which can emulate types which are not
// known at compile-time.
//
// Sometimes you want to be able to manipulate protocol types that you don't
// know about at compile time. It would be nice to be able to construct
// a Message object which implements the message type given by any arbitrary
// Descriptor. DynamicMessage provides this.
//
// As it turns out, a DynamicMessage needs to construct extra
// information about its type in order to operate. Most of this information
// can be shared between all DynamicMessages of the same type. But, caching
// this information in some sort of global map would be a bad idea, since
// the cached information for a particular descriptor could outlive the
// descriptor itself. To avoid this problem, DynamicMessageFactory
// encapsulates this "cache". All DynamicMessages of the same type created
// from the same factory will share the same support data. Any Descriptors
// used with a particular factory must outlive the factory.
class LIBPROTOBUF_EXPORT DynamicMessageFactory : public MessageFactory {
public:
// Construct a DynamicMessageFactory that will search for extensions in
// the DescriptorPool in which the exendee is defined.
DynamicMessageFactory();
// Construct a DynamicMessageFactory that will search for extensions in
// the given DescriptorPool.
DynamicMessageFactory(const DescriptorPool* pool);
~DynamicMessageFactory();
// implements MessageFactory ---------------------------------------
// Given a Descriptor, 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 and will
// be destroyed when the factory is destroyed. Also, any objects created
// by calling the prototype's New() method share some data with the
// prototype, so these must be destoyed before the DynamicMessageFactory
// is destroyed.
//
// The given descriptor must outlive the returned message, and hence must
// outlive the DynamicMessageFactory.
//
// Note that while GetPrototype() is idempotent, it is not const. This
// implies that it is not thread-safe to call GetPrototype() on the same
// DynamicMessageFactory in two different threads simultaneously. However,
// the returned objects are just as thread-safe as any other Message.
const Message* GetPrototype(const Descriptor* type);
private:
const DescriptorPool* pool_;
// This struct just contains a hash_map. We can't #include <google/protobuf/stubs/hash.h> from
// this header due to hacks needed for hash_map portability in the open source
// release. Namely, stubs/hash.h, which defines hash_map portably, is not a
// public header (for good reason), but dynamic_message.h is, and public
// headers may only #include other public headers.
struct PrototypeMap;
scoped_ptr<PrototypeMap> prototypes_;
GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(DynamicMessageFactory);
};
} // namespace protobuf
} // namespace google
#endif // GOOGLE_PROTOBUF_DYNAMIC_MESSAGE_H__
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