gzip: code shrink and speedup

function                                             old     new   delta
pack_gzip                                            908     861     -47

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 17 insertions, 12 deletions

diff --git a/archival/gzip.c b/archival/gzip.c
index 5812f4b27..fa7a79b04 100644
--- a/archival/gzip.c
+++ b/archival/gzip.c
@@ -478,15 +478,14 @@ static void put_16bit(ush w)
         put_8bit(w);
 }
 
+#define OPTIMIZED_PUT_32BIT (CONFIG_GZIP_FAST > 0 && BB_UNALIGNED_MEMACCESS_OK && BB_LITTLE_ENDIAN)
 static void put_32bit(ulg n)
 {
-#if CONFIG_GZIP_FAST > 0 \
- && BB_UNALIGNED_MEMACCESS_OK && BB_LITTLE_ENDIAN
+#if OPTIMIZED_PUT_32BIT
         unsigned outcnt = G1.outcnt;
         if (outcnt < OUTBUFSIZ-4) {
                 /* Common case */
-                uch *dst = &G1.outbuf[outcnt];
-                ulg *dst32 = (void*) dst;
+                ulg *dst32 = (void*) &G1.outbuf[outcnt];
                 *dst32 = n; /* unaligned LSB 32-bit store */
                 G1.outcnt = outcnt + 4;
                 return;
@@ -1951,7 +1950,7 @@ static void bi_init(void)
 /* ===========================================================================
  * Initialize the "longest match" routines for a new file
  */
-static void lm_init(ush * flagsp)
+static void lm_init(unsigned *flags16p)
 {
         unsigned j;
 
@@ -1960,7 +1959,7 @@ static void lm_init(ush * flagsp)
         /* prev will be initialized on the fly */
 
         /* speed options for the general purpose bit flag */
-        *flagsp |= 2;   /* FAST 4, SLOW 2 */
+        *flags16p |= 2; /* FAST 4, SLOW 2 */
         /* ??? reduce max_chain_length for binary files */
 
         //G1.strstart = 0; // globals are zeroed in pack_gzip()
@@ -2044,9 +2043,8 @@ static void ct_init(void)
         Assert(dist == 256, "ct_init: 256+dist != 512");
 
         /* Construct the codes of the static literal tree */
-        /* already zeroed - it's in bss
-        for (n = 0; n <= MAX_BITS; n++)
-                G2.bl_count[n] = 0; */
+        //for (n = 0; n <= MAX_BITS; n++) // globals are zeroed in pack_gzip()
+        //      G2.bl_count[n] = 0;
 
         n = 0;
         while (n <= 143) {
@@ -2088,7 +2086,7 @@ static void ct_init(void)
  */
 static void zip(void)
 {
-        ush deflate_flags = 0;  /* pkzip -es, -en or -ex equivalent */
+        unsigned deflate_flags;
 
         //G1.outcnt = 0; // globals are zeroed in pack_gzip()
 
@@ -2104,10 +2102,17 @@ static void zip(void)
 
         bi_init();
         ct_init();
+        deflate_flags = 0;  /* pkzip -es, -en or -ex equivalent */
         lm_init(&deflate_flags);
 
-        put_8bit(deflate_flags);        /* extra flags */
-        put_8bit(3);    /* OS identifier = 3 (Unix) */
+        put_16bit(deflate_flags | 0x300); /* extra flags. OS id = 3 (Unix) */
+
+#if OPTIMIZED_PUT_32BIT
+        /* put_32bit() performs 32bit stores. If we use it in send_bits()... */
+        if (BUF_SIZE > 16)
+                /* then all stores are misaligned, unless we flush the buffer now */
+                flush_outbuf();
+#endif
 
         deflate();