diff options
| author | Daniel Edgecumbe <git@esotericnonsense.com> | 2019-09-02 22:05:26 +0100 |
|---|---|---|
| committer | Denys Vlasenko <vda.linux@googlemail.com> | 2019-09-05 13:26:58 +0200 |
| commit | ca5d86d52c979cef05a614fb725870c10be9b265 (patch) | |
| tree | 0af03859c7ddd974d6b71834dd0fee10665a74cc /archival | |
| parent | de82f0b764de4720fed3378f2e5f938a3f4b9d18 (diff) | |
gzip: set compression flags correctly as per standard
With this change and CONFIG_GZIP_FAST=2, CONFIG_FEATURE_GZIP_LEVELS=y,
GNU gzip and BusyBox gzip now produce identical output at each compression
level (excluding 1..3, as BusyBox does not implement these levels).
Signed-off-by: Daniel Edgecumbe <git@esotericnonsense.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Diffstat (limited to 'archival')
| -rw-r--r-- | archival/gzip.c | 26 |
1 files changed, 18 insertions, 8 deletions
diff --git a/archival/gzip.c b/archival/gzip.c index 37db347b8..a543d8c36 100644 --- a/archival/gzip.c +++ b/archival/gzip.c @@ -259,6 +259,7 @@ enum { #if !ENABLE_FEATURE_GZIP_LEVELS + comp_level = 9, 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. @@ -334,14 +335,16 @@ struct globals { #define head (G1.prev + WSIZE) /* hash head (see deflate.c) */ #if ENABLE_FEATURE_GZIP_LEVELS + unsigned comp_level; unsigned max_chain_length; unsigned max_lazy_match; unsigned good_match; unsigned nice_match; +#define comp_level (G1.comp_level) #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) +#define good_match (G1.good_match) +#define nice_match (G1.nice_match) #endif /* =========================================================================== */ @@ -1919,7 +1922,7 @@ static void bi_init(void) /* =========================================================================== * Initialize the "longest match" routines for a new file */ -static void lm_init(unsigned *flags16p) +static void lm_init(void) { unsigned j; @@ -1927,8 +1930,6 @@ static void lm_init(unsigned *flags16p) memset(head, 0, HASH_SIZE * sizeof(*head)); /* prev will be initialized on the fly */ - /* speed options for the general purpose bit flag */ - *flags16p |= 2; /* FAST 4, SLOW 2 */ /* ??? reduce max_chain_length for binary files */ //G1.strstart = 0; // globals are zeroed in pack_gzip() @@ -2076,10 +2077,16 @@ static void zip(void) bi_init(); ct_init(); - deflate_flags = 0; /* pkzip -es, -en or -ex equivalent */ - lm_init(&deflate_flags); + lm_init(); - put_16bit(deflate_flags | 0x300); /* extra flags. OS id = 3 (Unix) */ + deflate_flags = 0x300; /* extra flags. OS id = 3 (Unix) */ +#if ENABLE_FEATURE_GZIP_LEVELS + /* Note that comp_level < 4 do not exist in this version of gzip */ + if (comp_level == 9) { + deflate_flags |= 0x02; /* SLOW flag */ + } +#endif + put_16bit(deflate_flags); /* The above 32-bit misaligns outbuf (10 bytes are stored), flush it */ flush_outbuf_if_32bit_optimized(); @@ -2224,6 +2231,9 @@ int gzip_main(int argc UNUSED_PARAM, char **argv) if (opt == 0) opt = 1 << 5; /* default: 6 */ opt = ffs(opt >> 4); /* Maps -1..-4 to [0], -5 to [1] ... -9 to [5] */ + + comp_level = opt + 4; + 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; |