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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__
+