gzip: code shrink

Use one memset to clear part of G1, and all of G2.

function                                             old     new   delta
pack_gzip                                            838     828     -10

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

1 files changed, 56 insertions, 52 deletions

diff --git a/archival/gzip.c b/archival/gzip.c
index d52167f84..9dc31e30b 100644
--- a/archival/gzip.c
+++ b/archival/gzip.c
@@ -300,6 +300,50 @@ enum {
 
 
 struct globals {
+/* =========================================================================== */
+/* global buffers, allocated once */
+
+#define DECLARE(type, array, size) \
+        type * array
+#define ALLOC(type, array, size) \
+        array = xzalloc((size_t)(((size)+1L)/2) * 2*sizeof(type))
+#define FREE(array) \
+        do { free(array); array = NULL; } while (0)
+
+        /* buffer for literals or lengths */
+        /* DECLARE(uch, l_buf, LIT_BUFSIZE); */
+        DECLARE(uch, l_buf, INBUFSIZ);
+
+        DECLARE(ush, d_buf, DIST_BUFSIZE);
+        DECLARE(uch, outbuf, OUTBUFSIZ);
+
+/* Sliding window. Input bytes are read into the second half of the window,
+ * and move to the first half later to keep a dictionary of at least WSIZE
+ * bytes. With this organization, matches are limited to a distance of
+ * WSIZE-MAX_MATCH bytes, but this ensures that IO is always
+ * performed with a length multiple of the block size. Also, it limits
+ * the window size to 64K, which is quite useful on MSDOS.
+ * To do: limit the window size to WSIZE+BSZ if SMALL_MEM (the code would
+ * be less efficient).
+ */
+        DECLARE(uch, window, 2L * WSIZE);
+
+/* Link to older string with same hash index. To limit the size of this
+ * array to 64K, this link is maintained only for the last 32K strings.
+ * An index in this array is thus a window index modulo 32K.
+ */
+        /* DECLARE(Pos, prev, WSIZE); */
+        DECLARE(ush, prev, 1L << BITS);
+
+/* Heads of the hash chains or 0. */
+        /* DECLARE(Pos, head, 1<<HASH_BITS); */
+#define head (G1.prev + WSIZE) /* hash head (see deflate.c) */
+
+/* =========================================================================== */
+/* all members below are zeroed out in pack_gzip() for each next file */
+
+        uint32_t crc;   /* shift register contents */
+        /*uint32_t *crc_32_tab;*/
 
 #if ENABLE_FEATURE_GZIP_LEVELS
         unsigned max_chain_length;
@@ -368,49 +412,6 @@ struct globals {
 #ifdef DEBUG
         ulg bits_sent;  /* bit length of the compressed data */
 #endif
-
-        /*uint32_t *crc_32_tab;*/
-        uint32_t crc;   /* shift register contents */
-
-/* ===========================================================================
- */
-#define DECLARE(type, array, size) \
-        type * array
-#define ALLOC(type, array, size) \
-        array = xzalloc((size_t)(((size)+1L)/2) * 2*sizeof(type))
-#define FREE(array) \
-        do { free(array); array = NULL; } while (0)
-
-        /* global buffers */
-
-        /* buffer for literals or lengths */
-        /* DECLARE(uch, l_buf, LIT_BUFSIZE); */
-        DECLARE(uch, l_buf, INBUFSIZ);
-
-        DECLARE(ush, d_buf, DIST_BUFSIZE);
-        DECLARE(uch, outbuf, OUTBUFSIZ);
-
-/* Sliding window. Input bytes are read into the second half of the window,
- * and move to the first half later to keep a dictionary of at least WSIZE
- * bytes. With this organization, matches are limited to a distance of
- * WSIZE-MAX_MATCH bytes, but this ensures that IO is always
- * performed with a length multiple of the block size. Also, it limits
- * the window size to 64K, which is quite useful on MSDOS.
- * To do: limit the window size to WSIZE+BSZ if SMALL_MEM (the code would
- * be less efficient).
- */
-        DECLARE(uch, window, 2L * WSIZE);
-
-/* Link to older string with same hash index. To limit the size of this
- * array to 64K, this link is maintained only for the last 32K strings.
- * An index in this array is thus a window index modulo 32K.
- */
-        /* DECLARE(Pos, prev, WSIZE); */
-        DECLARE(ush, prev, 1L << BITS);
-
-/* Heads of the hash chains or 0. */
-        /* DECLARE(Pos, head, 1<<HASH_BITS); */
-#define head (G1.prev + WSIZE) /* hash head (see deflate.c) */
 };
 
 #define G1 (*(ptr_to_globals - 1))
@@ -460,6 +461,7 @@ static void put_16bit(ush w)
         }
         *dst = (uch)w;
         w >>= 8;
+        G1.outcnt = ++outcnt;
 #else
         *dst = (uch)w;
         w >>= 8;
@@ -469,13 +471,13 @@ static void put_16bit(ush w)
                 G1.outcnt = outcnt + 2;
                 return;
         }
+        G1.outcnt = ++outcnt;
 #endif
 
         /* Slowpath: we will need to do flush_outbuf() */
-        G1.outcnt = ++outcnt;
         if (outcnt == OUTBUFSIZ)
-                flush_outbuf();
-        put_8bit(w);
+                flush_outbuf(); /* here */
+        put_8bit(w); /* or here */
 }
 
 #define OPTIMIZED_PUT_32BIT (CONFIG_GZIP_FAST > 0 && BB_UNALIGNED_MEMACCESS_OK && BB_LITTLE_ENDIAN)
@@ -2056,17 +2058,20 @@ static void ct_init(void)
                 G2.static_ltree[n++].Len = 9;
                 //G2.bl_count[9]++;
         }
-        G2.bl_count[9] = 255 - 143;
+        //G2.bl_count[9] = 255 - 143;
         while (n <= 279) {
                 G2.static_ltree[n++].Len = 7;
                 //G2.bl_count[7]++;
         }
-        G2.bl_count[7] = 279 - 255;
+        //G2.bl_count[7] = 279 - 255;
         while (n <= 287) {
                 G2.static_ltree[n++].Len = 8;
                 //G2.bl_count[8]++;
         }
-        G2.bl_count[8] = 287 - 279 + (143 + 1);
+        //G2.bl_count[8] += 287 - 279;
+        G2.bl_count[7] = 279 - 255;
+        G2.bl_count[8] = (143 + 1) + (287 - 279);
+        G2.bl_count[9] = 255 - 143;
         /* Codes 286 and 287 do not exist, but we must include them in the
          * tree construction to get a canonical Huffman tree (longest code
          * all ones)
@@ -2132,8 +2137,8 @@ static void zip(void)
 static
 IF_DESKTOP(long long) int FAST_FUNC pack_gzip(transformer_state_t *xstate UNUSED_PARAM)
 {
-        /* Reinit G1.xxx except pointers to allocated buffers */
-        memset(&G1, 0, offsetof(struct globals, l_buf));
+        /* Reinit G1.xxx except pointers to allocated buffers, and entire G2 */
+        memset(&G1.crc, 0, (sizeof(G1) - offsetof(struct globals, crc)) + sizeof(G2));
 
         /* Clear input and output buffers */
         //G1.outcnt = 0;
@@ -2143,7 +2148,6 @@ IF_DESKTOP(long long) int FAST_FUNC pack_gzip(transformer_state_t *xstate UNUSED
         //G1.isize = 0;
 
         /* Reinit G2.xxx */
-        memset(&G2, 0, sizeof(G2));
         G2.l_desc.dyn_tree     = G2.dyn_ltree;
         G2.l_desc.static_tree  = G2.static_ltree;
         G2.l_desc.extra_bits   = extra_lbits;