bbd53216f
Aaro Koskinen
2015-04-26
Subject
gzip: add support for compression levels 4-9
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Commit Diff GitHub →
archival/gzip.c+62 -10
| @@ -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"); | |
| } | |