1// Protocol Buffers - Google's data interchange format 2// Copyright 2008 Google Inc. All rights reserved. 3// http://code.google.com/p/protobuf/ 4// 5// Redistribution and use in source and binary forms, with or without 6// modification, are permitted provided that the following conditions are 7// met: 8// 9// * Redistributions of source code must retain the above copyright 10// notice, this list of conditions and the following disclaimer. 11// * Redistributions in binary form must reproduce the above 12// copyright notice, this list of conditions and the following disclaimer 13// in the documentation and/or other materials provided with the 14// distribution. 15// * Neither the name of Google Inc. nor the names of its 16// contributors may be used to endorse or promote products derived from 17// this software without specific prior written permission. 18// 19// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 20// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 21// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 22// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 23// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 24// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 25// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 26// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 27// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 28// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 29// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 31// Author: kenton@google.com (Kenton Varda) 32// Based on original Protocol Buffers design by 33// Sanjay Ghemawat, Jeff Dean, and others. 34// 35// Defines an implementation of Message which can emulate types which are not 36// known at compile-time. 37 38#ifndef GOOGLE_PROTOBUF_DYNAMIC_MESSAGE_H__ 39#define GOOGLE_PROTOBUF_DYNAMIC_MESSAGE_H__ 40 41#include <google/protobuf/message.h> 42#include <google/protobuf/stubs/common.h> 43 44namespace google { 45namespace protobuf { 46 47// Defined in other files. 48class Descriptor; // descriptor.h 49class DescriptorPool; // descriptor.h 50 51// Constructs implementations of Message which can emulate types which are not 52// known at compile-time. 53// 54// Sometimes you want to be able to manipulate protocol types that you don't 55// know about at compile time. It would be nice to be able to construct 56// a Message object which implements the message type given by any arbitrary 57// Descriptor. DynamicMessage provides this. 58// 59// As it turns out, a DynamicMessage needs to construct extra 60// information about its type in order to operate. Most of this information 61// can be shared between all DynamicMessages of the same type. But, caching 62// this information in some sort of global map would be a bad idea, since 63// the cached information for a particular descriptor could outlive the 64// descriptor itself. To avoid this problem, DynamicMessageFactory 65// encapsulates this "cache". All DynamicMessages of the same type created 66// from the same factory will share the same support data. Any Descriptors 67// used with a particular factory must outlive the factory. 68class LIBPROTOBUF_EXPORT DynamicMessageFactory : public MessageFactory { 69 public: 70 // Construct a DynamicMessageFactory that will search for extensions in 71 // the DescriptorPool in which the exendee is defined. 72 DynamicMessageFactory(); 73 74 // Construct a DynamicMessageFactory that will search for extensions in 75 // the given DescriptorPool. 76 // 77 // DEPRECATED: Use CodedInputStream::SetExtensionRegistry() to tell the 78 // parser to look for extensions in an alternate pool. However, note that 79 // this is almost never what you want to do. Almost all users should use 80 // the zero-arg constructor. 81 DynamicMessageFactory(const DescriptorPool* pool); 82 83 ~DynamicMessageFactory(); 84 85 // Call this to tell the DynamicMessageFactory that if it is given a 86 // Descriptor d for which: 87 // d->file()->pool() == DescriptorPool::generated_pool(), 88 // then it should delegate to MessageFactory::generated_factory() instead 89 // of constructing a dynamic implementation of the message. In theory there 90 // is no down side to doing this, so it may become the default in the future. 91 void SetDelegateToGeneratedFactory(bool enable) { 92 delegate_to_generated_factory_ = enable; 93 } 94 95 // implements MessageFactory --------------------------------------- 96 97 // Given a Descriptor, constructs the default (prototype) Message of that 98 // type. You can then call that message's New() method to construct a 99 // mutable message of that type. 100 // 101 // Calling this method twice with the same Descriptor returns the same 102 // object. The returned object remains property of the factory and will 103 // be destroyed when the factory is destroyed. Also, any objects created 104 // by calling the prototype's New() method share some data with the 105 // prototype, so these must be destoyed before the DynamicMessageFactory 106 // is destroyed. 107 // 108 // The given descriptor must outlive the returned message, and hence must 109 // outlive the DynamicMessageFactory. 110 // 111 // The method is thread-safe. 112 const Message* GetPrototype(const Descriptor* type); 113 114 private: 115 const DescriptorPool* pool_; 116 bool delegate_to_generated_factory_; 117 118 // This struct just contains a hash_map. We can't #include <google/protobuf/stubs/hash.h> from 119 // this header due to hacks needed for hash_map portability in the open source 120 // release. Namely, stubs/hash.h, which defines hash_map portably, is not a 121 // public header (for good reason), but dynamic_message.h is, and public 122 // headers may only #include other public headers. 123 struct PrototypeMap; 124 scoped_ptr<PrototypeMap> prototypes_; 125 mutable Mutex prototypes_mutex_; 126 127 friend class DynamicMessage; 128 const Message* GetPrototypeNoLock(const Descriptor* type); 129 130 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(DynamicMessageFactory); 131}; 132 133} // namespace protobuf 134 135} // namespace google 136#endif // GOOGLE_PROTOBUF_DYNAMIC_MESSAGE_H__ 137