Add support for compression levels 4-9.
function old new delta
gzip_main 191 306 +115
usage_messages 40461 40504 +43
pack_gzip 1924 1907 -17
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/1 up/down: 158/-17) Total: 141 bytes
The rationale for this feature is that the current hardcoded 9 level
is painfully slow with big files. Below are some examples when
compressing a rootfs tarball (368.9M uncompressed) with different levels
(gzip 1.6 compression time for comparison in parenthesis):
compression time compressed size
Without the patch: 1m22.534s 152.0M
With the patch, 9: 1m15.351s (1m7.419s) 152.0M (old bb default level)
8: 0m46.763s (0m43.335s) 152.1M
7: 0m28.519s (0m27.076s) 152.4M
6: 0m22.960s (0m21.879s) 152.8M (gzip default level)
5: 0m16.058s (0m14.740s) 153.9M
4: 0m12.484s (0m11.167s) 156.4M
If the compression level support is enabled, we make 6 the default
as with gzip 1.6.
Signed-off-by: Aaro Koskinen <[email protected]>
---
archival/gzip.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 55 insertions(+), 1 deletion(-)
diff --git a/archival/gzip.c b/archival/gzip.c
index bc1f9c6..e6161e2 100644
--- a/archival/gzip.c
+++ b/archival/gzip.c
@@ -62,14 +62,26 @@ 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 y
+//config: depends on GZIP
+//config: help
+//config: Enable support for compression levels 4-9. The default level
+//config: is 6 (without this option 9). If levels 1-3 are specified, 4
+//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 +264,8 @@ 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 +297,23 @@ 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 /* ENABLE_FEATURE_GZIP_LEVELS */
+
lng block_start;
/* window position at the beginning of the current output block. Gets
@@ -2161,6 +2187,22 @@ int gzip_main(int argc UNUSED_PARAM, char **argv)
#endif
{
unsigned opt;
+#ifdef ENABLE_FEATURE_GZIP_LEVELS
+ unsigned level;
+ const struct {
+ unsigned char good;
+ unsigned char chain_shift;
+ unsigned short lazy;
+ unsigned short nice;
+ } gzip_level_config[6] = {
+ {4, 4, 4, 16}, /* Level 4 */
+ {8, 5, 16, 32}, /* Level 5 */
+ {8, 7, 16, 128}, /* Level 6 */
+ {8, 8, 32, 128}, /* Level 7 */
+ {32, 10, 128, 258}, /* Level 8 */
+ {32, 12, 258, 258}, /* Level 9 */
+ };
+#endif /* ENABLE_FEATURE_GZIP_LEVELS */
#if ENABLE_FEATURE_GZIP_LONG_OPTIONS
applet_long_options = gzip_longopts;
@@ -2171,6 +2213,11 @@ int gzip_main(int argc UNUSED_PARAM, char **argv)
if (opt & 0x18) // -d and/or -t
return gunzip_main(argc, argv);
#endif
+#ifdef ENABLE_FEATURE_GZIP_LEVELS
+ /* Map 1..3 to 4 and make 6 a default. */
+ level = ffs(opt >> (4 + IF_GUNZIP(2)) & 0x1ff);
+ level = !level ? 6 : MAX(4, level);
+#endif /* ENABLE_FEATURE_GZIP_LEVELS */
option_mask32 &= 0x7; /* ignore -q, -0..9 */
//if (opt & 0x1) // -c
//if (opt & 0x2) // -f
@@ -2180,6 +2227,13 @@ int gzip_main(int argc UNUSED_PARAM, char **argv)
SET_PTR_TO_GLOBALS((char *)xzalloc(sizeof(struct globals)+sizeof(struct
globals2))
+ sizeof(struct globals));
+#ifdef ENABLE_FEATURE_GZIP_LEVELS
+ max_chain_length = 1 << gzip_level_config[level - 4].chain_shift;
+ good_match = gzip_level_config[level - 4].good;
+ max_lazy_match = gzip_level_config[level - 4].lazy;
+ nice_match = gzip_level_config[level - 4].nice;
+#endif /* ENABLE_FEATURE_GZIP_LEVELS */
+
/* Allocate all global buffers (for DYN_ALLOC option) */
ALLOC(uch, G1.l_buf, INBUFSIZ);
ALLOC(uch, G1.outbuf, OUTBUFSIZ);
--
2.3.3
_______________________________________________
busybox mailing list
[email protected]
http://lists.busybox.net/mailman/listinfo/busybox
