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// 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
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
// Definition of an abstract class that describes the interface between the
// encoding engine (which finds the best string matches between the source and
// target data) and the code table writer. The code table writer is passed a
// series of Add, Copy, and Run instructions and produces an output file in the
// desired format.
#include <stddef.h> // size_t
#include "checksum.h" // VCDChecksum
#include "google/format_extension_flags.h" // VCDiffFormatExtensionFlags
namespace open_vcdiff {
class OutputStringInterface;
// The method calls after construction should follow this pattern:
// {{Add|Copy|Run}* Output}*
// Output() will produce an encoding using the given series of Add, Copy,
// and/or Run instructions. One implementation of the interface
// (VCDiffCodeTableWriter) produces a VCDIFF delta window, but other
// implementations may be used to produce other output formats, or as test
// mocks, or to gather encoding statistics.
class CodeTableWriterInterface {
virtual ~CodeTableWriterInterface() { }
// Initializes the constructed object for use. It will return
// false if there was an error initializing the object, or true if it
// was successful. After the object has been initialized and used,
// Init() can be called again to restore the initial state of the object.
virtual bool Init(size_t dictionary_size) = 0;
// Writes the header to the output string.
virtual void WriteHeader(OutputStringInterface* out,
VCDiffFormatExtensionFlags format_extensions) = 0;
// Encode an ADD opcode with the "size" bytes starting at data
virtual void Add(const char* data, size_t size) = 0;
// Encode a COPY opcode with args "offset" (into dictionary) and "size" bytes.
virtual void Copy(int32_t offset, size_t size) = 0;
// Encode a RUN opcode for "size" copies of the value "byte".
virtual void Run(size_t size, unsigned char byte) = 0;
// Adds a checksum to the output.
virtual void AddChecksum(VCDChecksum checksum) = 0;
// Appends the encoded delta window to the output
// string. The output string is not null-terminated and may contain embedded
// '\0' characters.
virtual void Output(OutputStringInterface* out) = 0;
// Finishes encoding.
virtual void FinishEncoding(OutputStringInterface* out) = 0;
// Returns the number of target bytes processed, which is the sum of all the
// size arguments passed to Add(), Copy(), and Run().
virtual size_t target_length() const = 0;
} // namespace open_vcdiff