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gzip: fix compression level bug. Closes 9131

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fix broken logic to get the gzip_level_config value from options -1 to
-9.

This fixes an off-by-one bug that caused gzip -9 output bigger files
than the other compression levels.

It fixes so that compression level 1 to 3 are actually mapped to level 4
as comments say.

It also fixes that levels -4 to -9 is mapped to correct level and avoids
out-of-bounds access.

Signed-off-by: Natanael Copa <ncopa@alpinelinux.org>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Natanael Copa 2016-08-03 16:21:52 +02:00 committed by Denys Vlasenko
parent 7e6f9316a8
commit 71cfbce655
1 changed files with 1 additions and 4 deletions
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5
archival/gzip.c
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@ -2220,10 +2220,7 @@ int gzip_main(int argc UNUSED_PARAM, char **argv)
opt >>= ENABLE_GUNZIP ? 7 : 5; /* drop cfv[dt]qn bits */
if (opt == 0)
opt = 1 << 6; /* default: 6 */
/* Map 1..3 to 4 */
if (opt & 0x7)
opt |= 1 << 4;
opt = ffs(opt >> 3);
opt = ffs(opt >> 4); /* Maps -1..-4 to [0], -5 to [1] ... -9 to [5] */
max_chain_length = 1 << gzip_level_config[opt].chain_shift;
good_match = gzip_level_config[opt].good;
max_lazy_match = gzip_level_config[opt].lazy2 * 2;