1 /* Copyright 2016 Google Inc. All Rights Reserved.
2 Author: zip753@gmail.com (Ivan Nikulin)
3
4 Distributed under MIT license.
5 See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
6 */
7
8 /* API for reading distances from *.dist file.
9 The format of *.dist file is as follows: for each backward reference there is
10 a position-distance pair, also a copy length may be specified. Copy length is
11 prefixed with flag byte 0, position-distance pair is prefixed with flag
12 byte 1. Each number is a 32-bit integer. Copy length always comes before
13 position-distance pair. Standalone copy length is allowed, in this case it is
14 ignored. */
15
16 #ifndef BROTLI_RESEARCH_READ_DIST_H_
17 #define BROTLI_RESEARCH_READ_DIST_H_
18
19 #include <cstdio>
20 #include <cstdlib> /* exit, EXIT_FAILURE */
21
22 #if !defined(CHECK)
23 #define CHECK(X) if (!(X)) exit(EXIT_FAILURE);
24 #endif
25
26 /* Reads backwards reference from .dist file. Sets all missing fields to -1.
27 Returns false when EOF is met or input is corrupt. */
ReadBackwardReference(FILE * fin,int * copy,int * pos,int * dist)28 bool ReadBackwardReference(FILE* fin, int* copy, int* pos, int* dist) {
29 int c = getc(fin);
30 if (c == EOF) return false;
31 if (c == 0) {
32 CHECK(fread(copy, sizeof(int), 1, fin) == 1);
33 if ((c = getc(fin)) != 1) {
34 ungetc(c, fin);
35 *pos = *dist = -1;
36 } else {
37 CHECK(fread(pos, sizeof(int), 1, fin) == 1);
38 CHECK(fread(dist, sizeof(int), 1, fin) == 1);
39 }
40 } else if (c != 1) {
41 return false;
42 } else {
43 CHECK(fread(pos, sizeof(int), 1, fin) == 1);
44 CHECK(fread(dist, sizeof(int), 1, fin) == 1);
45 *copy = -1;
46 }
47 return true;
48 }
49
50 #endif /* BROTLI_RESEARCH_READ_DIST_H_ */
51