diffcore-delta: 64-byte-or-EOL ultrafast replacement.

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

diff --git a/diffcore-delta.c b/diffcore-delta.c
index 835d82c9939644faa808bb2f616136549af521db..ceb35c3276579b22b379f0fe1ccaf2a4a76fc61a 100644 (file)
--- a/diffcore-delta.c
+++ b/diffcore-delta.c
@@ -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)
+                                        unsigned long hashval, int cnt)
 {
        int bucket, lim;
        struct spanhash *h;
@@ -110,14 +110,14 @@ static struct spanhash_top *add_spanhash(struct spanhash_top *top,
                h = &(top->data[bucket++]);
                if (!h->cnt) {
                        h->hashval = hashval;
-                       h->cnt = 1;
+                       h->cnt = cnt;
                        top->free--;
                        if (top->free < 0)
                                return spanhash_rehash(top);
                        return top;
                }
                if (h->hashval == hashval) {
-                       h->cnt++;
+                       h->cnt += cnt;
                        return top;
                }
                if (lim <= bucket)
@@ -127,7 +127,7 @@ static struct spanhash_top *add_spanhash(struct spanhash_top *top,
 
 static struct spanhash_top *hash_chars(unsigned char *buf, unsigned long sz)
 {
-       int i;
+       int i, n;
        unsigned long accum1, accum2, hashval;
        struct spanhash_top *hash;
 
@@ -137,19 +137,20 @@ static struct spanhash_top *hash_chars(unsigned char *buf, unsigned long sz)
        hash->free = INITIAL_FREE(i);
        memset(hash->data, 0, sizeof(struct spanhash) * (1<<i));
 
-       /* an 8-byte shift register made of accum1 and accum2.  New
-        * bytes come at LSB of accum2, and shifted up to accum1
-        */
-       for (i = accum1 = accum2 = 0; i < 7; i++, sz--) {
-               accum1 = (accum1 << 8) | (accum2 >> 24);
-               accum2 = (accum2 << 8) | *buf++;
-       }
+       n = 0;
+       accum1 = accum2 = 0;
        while (sz) {
-               accum1 = (accum1 << 8) | (accum2 >> 24);
-               accum2 = (accum2 << 8) | *buf++;
-               hashval = (accum1 + accum2 * 0x61) % HASHBASE;
-               hash = add_spanhash(hash, hashval);
+               unsigned long c = *buf++;
                sz--;
+               accum1 = (accum1 << 7) | (accum2 >> 25);
+               accum2 = (accum2 << 7) | (accum1 >> 25);
+               accum1 += c;
+               if (++n < 64 && c != '\n')
+                       continue;
+               hashval = (accum1 + accum2 * 0x61) % HASHBASE;
+               hash = add_spanhash(hash, hashval, n);
+               n = 0;
+               accum1 = accum2 = 0;
        }
        return hash;
 }
@@ -166,9 +167,6 @@ int diffcore_count_changes(void *src, unsigned long src_size,
        struct spanhash_top *src_count, *dst_count;
        unsigned long sc, la;
 
-       if (src_size < 8 || dst_size < 8)
-               return -1;
-
        src_count = dst_count = NULL;
        if (src_count_p)
                src_count = *src_count_p;