get_sha1_hex() micro-optimization

The function appeared high on a gprof output for a rev-list run of
a non-trivial size, and it was an obvious low-hanging fruit.

The code is from Linus.

Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/sha1_file.c b/sha1_file.c
index 428d791ba8e2f62e3c30627a8f9463236c77cc60..b64b92de4e7a6c59edfb3e60ff1440a98cacdeea 100644 (file)
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -26,15 +26,43 @@ const unsigned char null_sha1[20];
 
 static unsigned int sha1_file_open_flag = O_NOATIME;
 
-static unsigned hexval(char c)
-{
-       if (c >= '0' && c <= '9')
-               return c - '0';
-       if (c >= 'a' && c <= 'f')
-               return c - 'a' + 10;
-       if (c >= 'A' && c <= 'F')
-               return c - 'A' + 10;
-       return ~0;
+static inline unsigned int hexval(unsigned int c)
+{
+       static signed char val[256] = {
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* 00-07 */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* 08-0f */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* 10-17 */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* 18-1f */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* 20-27 */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* 28-2f */
+                 0,  1,  2,  3,  4,  5,  6,  7,                /* 30-37 */
+                 8,  9, -1, -1, -1, -1, -1, -1,                /* 38-3f */
+                -1, 10, 11, 12, 13, 14, 15, -1,                /* 40-47 */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* 48-4f */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* 50-57 */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* 58-5f */
+                -1, 10, 11, 12, 13, 14, 15, -1,                /* 60-67 */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* 68-67 */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* 70-77 */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* 78-7f */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* 80-87 */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* 88-8f */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* 90-97 */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* 98-9f */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* a0-a7 */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* a8-af */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* b0-b7 */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* b8-bf */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* c0-c7 */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* c8-cf */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* d0-d7 */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* d8-df */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* e0-e7 */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* e8-ef */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* f0-f7 */
+                -1, -1, -1, -1, -1, -1, -1, -1,                /* f8-ff */
+       };
+       return val[c];
 }
 
 int get_sha1_hex(const char *hex, unsigned char *sha1)