gzip: add support for compression levels 4-9

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>

1 files changed, 62 insertions, 10 deletions

diff --git a/archival/gzip.c b/archival/gzip.c
index bc1f9c60b..42b2f0b2e 100644
--- a/archival/gzip.c
+++ b/archival/gzip.c
@@ -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");
 }