openvcdiff | 311c714 | 2008-08-26 19:29:25 +0000 | [diff] [blame] | 1 | // Copyright 2008 Google Inc. |
| 2 | // Author: Lincoln Smith |
| 3 | // |
| 4 | // Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | // you may not use this file except in compliance with the License. |
| 6 | // You may obtain a copy of the License at |
| 7 | // |
| 8 | // http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | // |
| 10 | // Unless required by applicable law or agreed to in writing, software |
| 11 | // distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | // See the License for the specific language governing permissions and |
| 14 | // limitations under the License. |
| 15 | |
| 16 | #ifndef OPEN_VCDIFF_OUTPUT_STRING_H_ |
| 17 | #define OPEN_VCDIFF_OUTPUT_STRING_H_ |
| 18 | |
openvcdiff | 28db807 | 2008-10-10 23:29:11 +0000 | [diff] [blame^] | 19 | #include <stddef.h> // size_t |
openvcdiff | 311c714 | 2008-08-26 19:29:25 +0000 | [diff] [blame] | 20 | |
| 21 | namespace open_vcdiff { |
| 22 | |
| 23 | // This interface allows clients of VCDiff[Streaming]Encoder and |
| 24 | // VCDiff[Streaming]Decoder to use different string types to receive the output |
| 25 | // of those interfaces. |
| 26 | // |
| 27 | // Only the following operations can be performed on an output string, and their |
| 28 | // semantics must be identical to the std::string methods of the same names: |
| 29 | // append() |
| 30 | // clear() |
| 31 | // push_back() |
| 32 | // size() |
| 33 | // |
| 34 | // The versions of these methods that take a std::string argument are not |
| 35 | // supported by OutputStringInterface. |
| 36 | // |
| 37 | // There is one additional operation that can be performed on an output string: |
| 38 | // ReserveAdditionalBytes(). This asks the underlying output type to reserve |
| 39 | // enough capacity for the number of additional bytes requested in addition to |
| 40 | // existing content. The decoder knows the total expected output size in |
| 41 | // advance, so one large ReserveAdditionalBytes() operation precedes many small |
| 42 | // append() operations. For output types that gain no advantage from knowing in |
| 43 | // advance how many bytes will be appended, ReserveAdditionalBytes() can be |
| 44 | // defined to do nothing. |
| 45 | class OutputStringInterface { |
| 46 | public: |
| 47 | virtual ~OutputStringInterface() { } |
| 48 | |
| 49 | virtual OutputStringInterface& append(const char* s, size_t n) = 0; |
| 50 | |
| 51 | virtual void clear() = 0; |
| 52 | |
| 53 | virtual void push_back(char c) = 0; |
| 54 | |
| 55 | virtual void ReserveAdditionalBytes(size_t res_arg) = 0; |
| 56 | |
| 57 | virtual size_t size() const = 0; |
| 58 | }; |
| 59 | |
| 60 | // This template can be used to wrap any class that supports the operations |
| 61 | // needed by OutputStringInterface, including std::string. A class that has |
| 62 | // different names or syntax for these operations will need specialized |
| 63 | // definitions of OutputString methods -- see output_string_types.h for some |
| 64 | // examples of how to do this. |
| 65 | template<class StringClass> |
| 66 | class OutputString : public OutputStringInterface { |
| 67 | public: |
| 68 | explicit OutputString(StringClass* impl) : impl_(impl) { } |
| 69 | |
| 70 | virtual ~OutputString() { } |
| 71 | |
| 72 | virtual OutputString& append(const char* s, size_t n) { |
| 73 | impl_->append(s, n); |
| 74 | return *this; |
| 75 | } |
| 76 | |
| 77 | virtual void clear() { |
| 78 | impl_->clear(); |
| 79 | } |
| 80 | |
| 81 | virtual void push_back(char c) { |
| 82 | impl_->push_back(c); |
| 83 | } |
| 84 | |
| 85 | virtual void ReserveAdditionalBytes(size_t res_arg) { |
| 86 | impl_->reserve(impl_->size() + res_arg); |
| 87 | } |
| 88 | |
| 89 | virtual size_t size() const { |
| 90 | return impl_->size(); |
| 91 | } |
| 92 | |
| 93 | protected: |
| 94 | StringClass* impl_; |
| 95 | |
| 96 | private: |
| 97 | // Making these private avoids implicit copy constructor & assignment operator |
| 98 | OutputString(const OutputString&); |
| 99 | void operator=(const OutputString&); |
| 100 | }; |
| 101 | |
| 102 | // Don't allow the OutputString template to be based upon a pointer to |
| 103 | // OutputStringInterface. Enforce this restriction by defining this class to |
| 104 | // lack any functions expected of an OutputString. |
| 105 | template<> class OutputString<OutputStringInterface> { }; |
| 106 | |
| 107 | } // namespace open_vcdiff |
| 108 | |
| 109 | #endif // OPEN_VCDIFF_OUTPUT_STRING_H_ |