linux-kernel - [PATCH] zlib_deflate/deftree: Remove bi

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Date:	Tue, 11 Aug 2015 13:32:10 +0800
From:	yalin wang <yalin.wang2010@...il.com>
To:	open list <linux-kernel@...r.kernel.org>
Subject: [PATCH] zlib_deflate/deftree: Remove bi_reverse()

This change remove bi_reverse() and use generic bitrev32() instead,
have better performance on some platforms.

Signed-off-by: yalin wang <yalin.wang2010@...il.com>
---
 lib/zlib_deflate/deftree.c |  6 +++---
 lib/zlib_deflate/defutil.h | 16 ----------------
 2 files changed, 3 insertions(+), 19 deletions(-)

diff --git a/lib/zlib_deflate/deftree.c b/lib/zlib_deflate/deftree.c
index ddf3482..9b1756b 100644
--- a/lib/zlib_deflate/deftree.c
+++ b/lib/zlib_deflate/deftree.c
@@ -35,6 +35,7 @@
 /* #include "deflate.h" */
 
 #include <linux/zutil.h>
+#include <linux/bitrev.h>
 #include "defutil.h"
 
 #ifdef DEBUG_ZLIB
@@ -146,7 +147,6 @@ static void send_all_trees (deflate_state *s, int lcodes, int dcodes,
 static void compress_block (deflate_state *s, ct_data *ltree,
                            ct_data *dtree);
 static void set_data_type  (deflate_state *s);
-static unsigned bi_reverse (unsigned value, int length);
 static void bi_windup      (deflate_state *s);
 static void bi_flush       (deflate_state *s);
 static void copy_block     (deflate_state *s, char *buf, unsigned len,
@@ -284,7 +284,7 @@ static void tr_static_init(void)
     /* The static distance tree is trivial: */
     for (n = 0; n < D_CODES; n++) {
         static_dtree[n].Len = 5;
-        static_dtree[n].Code = bi_reverse((unsigned)n, 5);
+        static_dtree[n].Code = bitrev32((u32)n) >> (32 - 5);
     }
     static_init_done = 1;
 }
@@ -520,7 +520,7 @@ static void gen_codes(
         int len = tree[n].Len;
         if (len == 0) continue;
         /* Now reverse the bits */
-        tree[n].Code = bi_reverse(next_code[len]++, len);
+        tree[n].Code = bitrev32((u32)(next_code[len]++)) >> (32 - len);
 
         Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
              n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
diff --git a/lib/zlib_deflate/defutil.h b/lib/zlib_deflate/defutil.h
index b640b64..a8c3708 100644
--- a/lib/zlib_deflate/defutil.h
+++ b/lib/zlib_deflate/defutil.h
@@ -293,22 +293,6 @@ void zlib_tr_stored_type_only (deflate_state *);
 }
 
 /* ===========================================================================
- * Reverse the first len bits of a code, using straightforward code (a faster
- * method would use a table)
- * IN assertion: 1 <= len <= 15
- */
-static inline unsigned bi_reverse(unsigned code, /* the value to invert */
-				  int len)       /* its bit length */
-{
-    register unsigned res = 0;
-    do {
-        res |= code & 1;
-        code >>= 1, res <<= 1;
-    } while (--len > 0);
-    return res >> 1;
-}
-
-/* ===========================================================================
  * Flush the bit buffer, keeping at most 7 bits in it.
  */
 static inline void bi_flush(deflate_state *s)
-- 
1.9.1

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