137 lines
6.0 KiB
C++
137 lines
6.0 KiB
C++
// Protocol Buffers - Google's data interchange format
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// Copyright 2008 Google Inc. All rights reserved.
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// http://code.google.com/p/protobuf/
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following disclaimer
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// in the documentation and/or other materials provided with the
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// distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived from
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// this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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// Author: kenton@google.com (Kenton Varda)
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// Based on original Protocol Buffers design by
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// Sanjay Ghemawat, Jeff Dean, and others.
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//
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// Defines an implementation of Message which can emulate types which are not
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// known at compile-time.
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#ifndef GOOGLE_PROTOBUF_DYNAMIC_MESSAGE_H__
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#define GOOGLE_PROTOBUF_DYNAMIC_MESSAGE_H__
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#include <google/protobuf/message.h>
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#include <google/protobuf/stubs/common.h>
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namespace google {
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namespace protobuf {
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// Defined in other files.
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class Descriptor; // descriptor.h
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class DescriptorPool; // descriptor.h
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// Constructs implementations of Message which can emulate types which are not
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// known at compile-time.
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//
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// Sometimes you want to be able to manipulate protocol types that you don't
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// know about at compile time. It would be nice to be able to construct
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// a Message object which implements the message type given by any arbitrary
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// Descriptor. DynamicMessage provides this.
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//
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// As it turns out, a DynamicMessage needs to construct extra
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// information about its type in order to operate. Most of this information
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// can be shared between all DynamicMessages of the same type. But, caching
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// this information in some sort of global map would be a bad idea, since
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// the cached information for a particular descriptor could outlive the
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// descriptor itself. To avoid this problem, DynamicMessageFactory
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// encapsulates this "cache". All DynamicMessages of the same type created
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// from the same factory will share the same support data. Any Descriptors
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// used with a particular factory must outlive the factory.
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class LIBPROTOBUF_EXPORT DynamicMessageFactory : public MessageFactory {
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public:
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// Construct a DynamicMessageFactory that will search for extensions in
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// the DescriptorPool in which the exendee is defined.
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DynamicMessageFactory();
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// Construct a DynamicMessageFactory that will search for extensions in
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// the given DescriptorPool.
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//
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// DEPRECATED: Use CodedInputStream::SetExtensionRegistry() to tell the
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// parser to look for extensions in an alternate pool. However, note that
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// this is almost never what you want to do. Almost all users should use
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// the zero-arg constructor.
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DynamicMessageFactory(const DescriptorPool* pool);
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~DynamicMessageFactory();
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// Call this to tell the DynamicMessageFactory that if it is given a
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// Descriptor d for which:
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// d->file()->pool() == DescriptorPool::generated_pool(),
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// then it should delegate to MessageFactory::generated_factory() instead
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// of constructing a dynamic implementation of the message. In theory there
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// is no down side to doing this, so it may become the default in the future.
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void SetDelegateToGeneratedFactory(bool enable) {
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delegate_to_generated_factory_ = enable;
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}
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// implements MessageFactory ---------------------------------------
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// Given a Descriptor, constructs the default (prototype) Message of that
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// type. You can then call that message's New() method to construct a
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// mutable message of that type.
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//
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// Calling this method twice with the same Descriptor returns the same
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// object. The returned object remains property of the factory and will
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// be destroyed when the factory is destroyed. Also, any objects created
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// by calling the prototype's New() method share some data with the
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// prototype, so these must be destoyed before the DynamicMessageFactory
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// is destroyed.
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//
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// The given descriptor must outlive the returned message, and hence must
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// outlive the DynamicMessageFactory.
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//
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// The method is thread-safe.
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const Message* GetPrototype(const Descriptor* type);
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private:
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const DescriptorPool* pool_;
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bool delegate_to_generated_factory_;
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// This struct just contains a hash_map. We can't #include <google/protobuf/stubs/hash.h> from
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// this header due to hacks needed for hash_map portability in the open source
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// release. Namely, stubs/hash.h, which defines hash_map portably, is not a
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// public header (for good reason), but dynamic_message.h is, and public
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// headers may only #include other public headers.
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struct PrototypeMap;
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scoped_ptr<PrototypeMap> prototypes_;
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mutable Mutex prototypes_mutex_;
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friend class DynamicMessage;
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const Message* GetPrototypeNoLock(const Descriptor* type);
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GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(DynamicMessageFactory);
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};
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} // namespace protobuf
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} // namespace google
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#endif // GOOGLE_PROTOBUF_DYNAMIC_MESSAGE_H__
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