| // Protocol Buffers - Google's data interchange format |
| // Copyright 2008 Google Inc. |
| // http://code.google.com/p/protobuf/ |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| // 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__ |
| |