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
29namespace open_vcdiff {
30
31class 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//
42class CodeTableWriterInterface {
43 public:
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