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gzip: add support for compression levels 4-9

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function                                             old     new   delta
gzip_main                                            192     282     +90
static.gzip_level_config                               -      24     +24
packed_usage                                       30439   30459     +20
fill_window                                          216     220      +4
pack_gzip                                           1789    1729     -60
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 3/1 up/down: 138/-60)            Total: 78 bytes

Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Aaro Koskinen 2015-04-26 14:22:05 +02:00 committed by Denys Vlasenko
parent 93b98ff572
commit bbd53216f8
1 changed files with 62 additions and 10 deletions
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72
archival/gzip.c
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@ -62,14 +62,27 @@ aa: 85.1% -- replaced with aa.gz
//config: 1: larger buffers, larger hash-tables
//config: 2: larger buffers, largest hash-tables
//config: Larger models may give slightly better compression
//config:
//config:config FEATURE_GZIP_LEVELS
//config: bool "Enable compression levels"
//config: default n
//config: depends on GZIP
//config: help
//config: Enable support for compression levels 4-9. The default level
//config: is 6. If levels 1-3 are specified, 4 is used.
//config: If this option is not selected, -N options are ignored and -9
//config: is used.
//applet:IF_GZIP(APPLET(gzip, BB_DIR_BIN, BB_SUID_DROP))
//kbuild:lib-$(CONFIG_GZIP) += gzip.o
//usage:#define gzip_trivial_usage
//usage: "[-cfd] [FILE]..."
//usage: "[-cfd" IF_FEATURE_GZIP_LEVELS("123456789") "] [FILE]..."
//usage:#define gzip_full_usage "\n\n"
//usage: "Compress FILEs (or stdin)\n"
//usage: IF_FEATURE_GZIP_LEVELS(
//usage: "\n -1..9 Compression level"
//usage: )
//usage: "\n -d Decompress"
//usage: "\n -c Write to stdout"
//usage: "\n -f Force"
@ -252,6 +265,8 @@ enum {
* input file length plus MIN_LOOKAHEAD.
*/
#ifndef ENABLE_FEATURE_GZIP_LEVELS
max_chain_length = 4096,
/* To speed up deflation, hash chains are never searched beyond this length.
* A higher limit improves compression ratio but degrades the speed.
@ -283,11 +298,23 @@ enum {
* For deflate_fast() (levels <= 3) good is ignored and lazy has a different
* meaning.
*/
#endif /* ENABLE_FEATURE_GZIP_LEVELS */
};
struct globals {
#ifdef ENABLE_FEATURE_GZIP_LEVELS
unsigned max_chain_length;
unsigned max_lazy_match;
unsigned good_match;
unsigned nice_match;
#define max_chain_length (G1.max_chain_length)
#define max_lazy_match (G1.max_lazy_match)
#define good_match (G1.good_match)
#define nice_match (G1.nice_match)
#endif
lng block_start;
/* window position at the beginning of the current output block. Gets
@ -2161,24 +2188,48 @@ int gzip_main(int argc UNUSED_PARAM, char **argv)
#endif
{
unsigned opt;
#ifdef ENABLE_FEATURE_GZIP_LEVELS
static const struct {
uint8_t good;
uint8_t chain_shift;
uint8_t lazy2;
uint8_t nice2;
} gzip_level_config[6] = {
{4, 4, 4/2, 16/2}, /* Level 4 */
{8, 5, 16/2, 32/2}, /* Level 5 */
{8, 7, 16/2, 128/2}, /* Level 6 */
{8, 8, 32/2, 128/2}, /* Level 7 */
{32, 10, 128/2, 258/2}, /* Level 8 */
{32, 12, 258/2, 258/2}, /* Level 9 */
};
#endif
SET_PTR_TO_GLOBALS((char *)xzalloc(sizeof(struct globals)+sizeof(struct globals2))
+ sizeof(struct globals));
#if ENABLE_FEATURE_GZIP_LONG_OPTIONS
applet_long_options = gzip_longopts;
#endif
/* Must match bbunzip's constants OPT_STDOUT, OPT_FORCE! */
opt = getopt32(argv, "cfv" IF_GUNZIP("dt") "q123456789n");
opt = getopt32(argv, "cfv" IF_GUNZIP("dt") "qn123456789");
#if ENABLE_GUNZIP /* gunzip_main may not be visible... */
if (opt & 0x18) // -d and/or -t
return gunzip_main(argc, argv);
#endif
option_mask32 &= 0x7; /* ignore -q, -0..9 */
//if (opt & 0x1) // -c
//if (opt & 0x2) // -f
//if (opt & 0x4) // -v
argv += optind;
SET_PTR_TO_GLOBALS((char *)xzalloc(sizeof(struct globals)+sizeof(struct globals2))
+ sizeof(struct globals));
#ifdef ENABLE_FEATURE_GZIP_LEVELS
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);
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;
nice_match = gzip_level_config[opt].nice2 * 2;
#endif
option_mask32 &= 0x7; /* retain only -cfv */
/* Allocate all global buffers (for DYN_ALLOC option) */
ALLOC(uch, G1.l_buf, INBUFSIZ);
@ -2190,5 +2241,6 @@ int gzip_main(int argc UNUSED_PARAM, char **argv)
/* Initialize the CRC32 table */
global_crc32_table = crc32_filltable(NULL, 0);
argv += optind;
return bbunpack(argv, pack_gzip, append_ext, "gz");
}