brotli/research/read_dist.h

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/* Copyright 2016 Google Inc. All Rights Reserved.
Author: zip753@gmail.com (Ivan Nikulin)
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Distributed under MIT license.
See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
*/
/* API for reading distances from *.dist file.
The format of *.dist file is as follows: for each backward reference there is
a position-distance pair, also a copy length may be specified. Copy length is
prefixed with flag byte 0, position-distance pair is prefixed with flag
byte 1. Each number is a 32-bit integer. Copy length always comes before
position-distance pair. Standalone copy length is allowed, in this case it is
ignored. */
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#ifndef BROTLI_RESEARCH_READ_DIST_H_
#define BROTLI_RESEARCH_READ_DIST_H_
#include <cstdio>
#include <cstdlib> /* exit, EXIT_FAILURE */
#if !defined(CHECK)
#define CHECK(X) if (!(X)) exit(EXIT_FAILURE);
#endif
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/* Reads backwards reference from .dist file. Sets all missing fields to -1.
Returns false when EOF is met or input is corrupt. */
bool ReadBackwardReference(FILE* fin, int* copy, int* pos, int* dist) {
int c = getc(fin);
if (c == EOF) return false;
if (c == 0) {
CHECK(fread(copy, sizeof(int), 1, fin) == 1);
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if ((c = getc(fin)) != 1) {
ungetc(c, fin);
*pos = *dist = -1;
} else {
CHECK(fread(pos, sizeof(int), 1, fin) == 1);
CHECK(fread(dist, sizeof(int), 1, fin) == 1);
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}
} else if (c != 1) {
return false;
} else {
CHECK(fread(pos, sizeof(int), 1, fin) == 1);
CHECK(fread(dist, sizeof(int), 1, fin) == 1);
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*copy = -1;
}
return true;
}
#endif /* BROTLI_RESEARCH_READ_DIST_H_ */