| // Copyright 2008 Google Inc. |
| // Author: Lincoln Smith |
| // |
| // 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. |
| |
| #ifndef OPEN_VCDIFF_OUTPUT_STRING_H_ |
| #define OPEN_VCDIFF_OUTPUT_STRING_H_ |
| |
| #include <cstddef> // size_t |
| |
| namespace open_vcdiff { |
| |
| // This interface allows clients of VCDiff[Streaming]Encoder and |
| // VCDiff[Streaming]Decoder to use different string types to receive the output |
| // of those interfaces. |
| // |
| // Only the following operations can be performed on an output string, and their |
| // semantics must be identical to the std::string methods of the same names: |
| // append() |
| // clear() |
| // push_back() |
| // size() |
| // |
| // The versions of these methods that take a std::string argument are not |
| // supported by OutputStringInterface. |
| // |
| // There is one additional operation that can be performed on an output string: |
| // ReserveAdditionalBytes(). This asks the underlying output type to reserve |
| // enough capacity for the number of additional bytes requested in addition to |
| // existing content. The decoder knows the total expected output size in |
| // advance, so one large ReserveAdditionalBytes() operation precedes many small |
| // append() operations. For output types that gain no advantage from knowing in |
| // advance how many bytes will be appended, ReserveAdditionalBytes() can be |
| // defined to do nothing. |
| class OutputStringInterface { |
| public: |
| virtual ~OutputStringInterface() { } |
| |
| virtual OutputStringInterface& append(const char* s, size_t n) = 0; |
| |
| virtual void clear() = 0; |
| |
| virtual void push_back(char c) = 0; |
| |
| virtual void ReserveAdditionalBytes(size_t res_arg) = 0; |
| |
| virtual size_t size() const = 0; |
| }; |
| |
| // This template can be used to wrap any class that supports the operations |
| // needed by OutputStringInterface, including std::string. A class that has |
| // different names or syntax for these operations will need specialized |
| // definitions of OutputString methods -- see output_string_types.h for some |
| // examples of how to do this. |
| template<class StringClass> |
| class OutputString : public OutputStringInterface { |
| public: |
| explicit OutputString(StringClass* impl) : impl_(impl) { } |
| |
| virtual ~OutputString() { } |
| |
| virtual OutputString& append(const char* s, size_t n) { |
| impl_->append(s, n); |
| return *this; |
| } |
| |
| virtual void clear() { |
| impl_->clear(); |
| } |
| |
| virtual void push_back(char c) { |
| impl_->push_back(c); |
| } |
| |
| virtual void ReserveAdditionalBytes(size_t res_arg) { |
| impl_->reserve(impl_->size() + res_arg); |
| } |
| |
| virtual size_t size() const { |
| return impl_->size(); |
| } |
| |
| protected: |
| StringClass* impl_; |
| |
| private: |
| // Making these private avoids implicit copy constructor & assignment operator |
| OutputString(const OutputString&); |
| void operator=(const OutputString&); |
| }; |
| |
| // Don't allow the OutputString template to be based upon a pointer to |
| // OutputStringInterface. Enforce this restriction by defining this class to |
| // lack any functions expected of an OutputString. |
| template<> class OutputString<OutputStringInterface> { }; |
| |
| } // namespace open_vcdiff |
| |
| #endif // OPEN_VCDIFF_OUTPUT_STRING_H_ |