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 // Definition of an abstract class that describes the interface between the 17 // encoding engine (which finds the best string matches between the source and 18 // target data) and the code table writer. The code table writer is passed a 19 // series of Add, Copy, and Run instructions and produces an output file in the 20 // desired format. 21 22 #ifndef OPEN_VCDIFF_CODETABLEWRITER_INTERFACE_H_ 23 #define OPEN_VCDIFF_CODETABLEWRITER_INTERFACE_H_ 24 25 #include <stddef.h> // size_t 26 #include "checksum.h" // VCDChecksum 27 #include "google/format_extension_flags.h" // VCDiffFormatExtensionFlags 28 29 namespace open_vcdiff { 30 31 class OutputStringInterface; 32 33 // The method calls after construction should follow this pattern: 34 // {{Add|Copy|Run}* Output}* 35 // 36 // Output() will produce an encoding using the given series of Add, Copy, 37 // and/or Run instructions. One implementation of the interface 38 // (VCDiffCodeTableWriter) produces a VCDIFF delta window, but other 39 // implementations may be used to produce other output formats, or as test 40 // mocks, or to gather encoding statistics. 41 // 42 class CodeTableWriterInterface { 43 public: ~CodeTableWriterInterface()44 virtual ~CodeTableWriterInterface() { } 45 46 // Initializes the constructed object for use. It will return 47 // false if there was an error initializing the object, or true if it 48 // was successful. After the object has been initialized and used, 49 // Init() can be called again to restore the initial state of the object. 50 virtual bool Init(size_t dictionary_size) = 0; 51 52 // Writes the header to the output string. 53 virtual void WriteHeader(OutputStringInterface* out, 54 VCDiffFormatExtensionFlags format_extensions) = 0; 55 56 // Encode an ADD opcode with the "size" bytes starting at data 57 virtual void Add(const char* data, size_t size) = 0; 58 59 // Encode a COPY opcode with args "offset" (into dictionary) and "size" bytes. 60 virtual void Copy(int32_t offset, size_t size) = 0; 61 62 // Encode a RUN opcode for "size" copies of the value "byte". 63 virtual void Run(size_t size, unsigned char byte) = 0; 64 65 // Adds a checksum to the output. 66 virtual void AddChecksum(VCDChecksum checksum) = 0; 67 68 // Appends the encoded delta window to the output 69 // string. The output string is not null-terminated and may contain embedded 70 // '\0' characters. 71 virtual void Output(OutputStringInterface* out) = 0; 72 73 // Finishes encoding. 74 virtual void FinishEncoding(OutputStringInterface* out) = 0; 75 76 // Returns the number of target bytes processed, which is the sum of all the 77 // size arguments passed to Add(), Copy(), and Run(). 78 virtual size_t target_length() const = 0; 79 }; 80 81 } // namespace open_vcdiff 82 83 #endif // OPEN_VCDIFF_CODETABLEWRITER_INTERFACE_H_ 84