1 // Protocol Buffers - Google's data interchange format 2 // Copyright 2008 Google Inc. All rights reserved. 3 // https://developers.google.com/protocol-buffers/ 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 <memory> 42 43 #include <google/protobuf/message.h> 44 #include <google/protobuf/stubs/common.h> 45 46 namespace google { 47 namespace protobuf { 48 49 // Defined in other files. 50 class Descriptor; // descriptor.h 51 class DescriptorPool; // descriptor.h 52 53 // Constructs implementations of Message which can emulate types which are not 54 // known at compile-time. 55 // 56 // Sometimes you want to be able to manipulate protocol types that you don't 57 // know about at compile time. It would be nice to be able to construct 58 // a Message object which implements the message type given by any arbitrary 59 // Descriptor. DynamicMessage provides this. 60 // 61 // As it turns out, a DynamicMessage needs to construct extra 62 // information about its type in order to operate. Most of this information 63 // can be shared between all DynamicMessages of the same type. But, caching 64 // this information in some sort of global map would be a bad idea, since 65 // the cached information for a particular descriptor could outlive the 66 // descriptor itself. To avoid this problem, DynamicMessageFactory 67 // encapsulates this "cache". All DynamicMessages of the same type created 68 // from the same factory will share the same support data. Any Descriptors 69 // used with a particular factory must outlive the factory. 70 class LIBPROTOBUF_EXPORT DynamicMessageFactory : public MessageFactory { 71 public: 72 // Construct a DynamicMessageFactory that will search for extensions in 73 // the DescriptorPool in which the extendee is defined. 74 DynamicMessageFactory(); 75 76 // Construct a DynamicMessageFactory that will search for extensions in 77 // the given DescriptorPool. 78 // 79 // DEPRECATED: Use CodedInputStream::SetExtensionRegistry() to tell the 80 // parser to look for extensions in an alternate pool. However, note that 81 // this is almost never what you want to do. Almost all users should use 82 // the zero-arg constructor. 83 DynamicMessageFactory(const DescriptorPool* pool); 84 85 ~DynamicMessageFactory(); 86 87 // Call this to tell the DynamicMessageFactory that if it is given a 88 // Descriptor d for which: 89 // d->file()->pool() == DescriptorPool::generated_pool(), 90 // then it should delegate to MessageFactory::generated_factory() instead 91 // of constructing a dynamic implementation of the message. In theory there 92 // is no down side to doing this, so it may become the default in the future. SetDelegateToGeneratedFactory(bool enable)93 void SetDelegateToGeneratedFactory(bool enable) { 94 delegate_to_generated_factory_ = enable; 95 } 96 97 // implements MessageFactory --------------------------------------- 98 99 // Given a Descriptor, constructs the default (prototype) Message of that 100 // type. You can then call that message's New() method to construct a 101 // mutable message of that type. 102 // 103 // Calling this method twice with the same Descriptor returns the same 104 // object. The returned object remains property of the factory and will 105 // be destroyed when the factory is destroyed. Also, any objects created 106 // by calling the prototype's New() method share some data with the 107 // prototype, so these must be destroyed before the DynamicMessageFactory 108 // is destroyed. 109 // 110 // The given descriptor must outlive the returned message, and hence must 111 // outlive the DynamicMessageFactory. 112 // 113 // The method is thread-safe. 114 const Message* GetPrototype(const Descriptor* type); 115 116 private: 117 const DescriptorPool* pool_; 118 bool delegate_to_generated_factory_; 119 120 // This struct just contains a hash_map. We can't #include <google/protobuf/stubs/hash.h> from 121 // this header due to hacks needed for hash_map portability in the open source 122 // release. Namely, stubs/hash.h, which defines hash_map portably, is not a 123 // public header (for good reason), but dynamic_message.h is, and public 124 // headers may only #include other public headers. 125 struct PrototypeMap; 126 scoped_ptr<PrototypeMap> prototypes_; 127 mutable Mutex prototypes_mutex_; 128 129 friend class DynamicMessage; 130 const Message* GetPrototypeNoLock(const Descriptor* type); 131 132 // Construct default oneof instance for reflection usage if oneof 133 // is defined. 134 static void ConstructDefaultOneofInstance(const Descriptor* type, 135 const int offsets[], 136 void* default_oneof_instance); 137 // Delete default oneof instance. Called by ~DynamicMessageFactory. 138 static void DeleteDefaultOneofInstance(const Descriptor* type, 139 const int offsets[], 140 void* default_oneof_instance); 141 142 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(DynamicMessageFactory); 143 }; 144 145 } // namespace protobuf 146 147 } // namespace google 148 #endif // GOOGLE_PROTOBUF_DYNAMIC_MESSAGE_H__ 149