diffcore-delta: 64-byte-or-EOL ultrafast replacement (hash fix).

The rotating 64-bit number was not really rotating, and worse
yet ulong was longer than 64-bit on 64-bit architectures X-<.

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

diff --git a/diffcore-delta.c b/diffcore-delta.c
index ceb35c3..7338a40 100644 (file)
--- a/diffcore-delta.c
+++ b/diffcore-delta.c
@@ -40,8 +40,8 @@
 #define HASHBASE 107927
 
 struct spanhash {
-       unsigned long hashval;
-       unsigned long cnt;
+       unsigned int hashval;
+       unsigned int cnt;
 };
 struct spanhash_top {
        int alloc_log2;
@@ -50,7 +50,7 @@ struct spanhash_top {
 };
 
 static struct spanhash *spanhash_find(struct spanhash_top *top,
-                                     unsigned long hashval)
+                                     unsigned int hashval)
 {
        int sz = 1 << top->alloc_log2;
        int bucket = hashval & (sz - 1);
@@ -99,7 +99,7 @@ static struct spanhash_top *spanhash_rehash(struct spanhash_top *orig)
 }
 
 static struct spanhash_top *add_spanhash(struct spanhash_top *top,
-                                        unsigned long hashval, int cnt)
+                                        unsigned int hashval, int cnt)
 {
        int bucket, lim;
        struct spanhash *h;
@@ -125,10 +125,10 @@ static struct spanhash_top *add_spanhash(struct spanhash_top *top,
        }
 }
 
-static struct spanhash_top *hash_chars(unsigned char *buf, unsigned long sz)
+static struct spanhash_top *hash_chars(unsigned char *buf, unsigned int sz)
 {
        int i, n;
-       unsigned long accum1, accum2, hashval;
+       unsigned int accum1, accum2, hashval;
        struct spanhash_top *hash;
 
        i = INITIAL_HASH_SIZE;
@@ -140,10 +140,11 @@ static struct spanhash_top *hash_chars(unsigned char *buf, unsigned long sz)
        n = 0;
        accum1 = accum2 = 0;
        while (sz) {
-               unsigned long c = *buf++;
+               unsigned int c = *buf++;
+               unsigned int old_1 = accum1;
                sz--;
-               accum1 = (accum1 << 7) | (accum2 >> 25);
-               accum2 = (accum2 << 7) | (accum1 >> 25);
+               accum1 = (accum1 << 7) ^ (accum2 >> 25);
+               accum2 = (accum2 << 7) ^ (old_1 >> 25);
                accum1 += c;
                if (++n < 64 && c != '\n')
                        continue;