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Fix a bug in ZLIB_DEBUG compiles in check_match().

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This avoids trying to compare a match starting one byte before the
current window. Thanks to @zmodem (Hans) for discovering this.
This commit is contained in:
Mark Adler 2024-01-19 12:19:53 -08:00
parent 7b632b486a
commit 7af6320ad7
1 changed files with 14 additions and 6 deletions
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20
deflate.c
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@ -1556,13 +1556,21 @@ local uInt longest_match(deflate_state *s, IPos cur_match) {
*/
local void check_match(deflate_state *s, IPos start, IPos match, int length) {
/* check that the match is indeed a match */
if (zmemcmp(s->window + match,
s->window + start, length) != EQUAL) {
fprintf(stderr, " start %u, match %u, length %d\n",
start, match, length);
Bytef *back = s->window + (int)match, *here = s->window + start;
IPos len = length;
if (match == (IPos)-1) {
/* match starts one byte before the current window -- just compare the
subsequent length-1 bytes */
back++;
here++;
len--;
}
if (zmemcmp(back, here, len) != EQUAL) {
fprintf(stderr, " start %u, match %d, length %d\n",
start, (int)match, length);
do {
fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);
} while (--length != 0);
fprintf(stderr, "(%02x %02x)", *back++, *here++);
} while (--len != 0);
z_error("invalid match");
}
if (z_verbose > 1) {