an optimization that tries to make rsync choose adjacent matches if

multiple matching blocks are available. This make the run-length
coding of the output more efficient.

diff --git a/match.c b/match.c
index 29b5251..38e8aa0 100644 (file)
--- a/match.c
+++ b/match.c
@@ -130,12 +130,16 @@ static void hash_search(int f,struct sum_struct *s,
                        struct map_struct *buf,OFF_T len)
 {
        OFF_T offset;
-       int j,k;
+       int j,k, last_i;
        int end;
        char sum2[SUM_LENGTH];
        uint32 s1, s2, sum; 
        schar *map;
 
+       /* last_i is used to encourage adjacent matches, allowing the RLL coding of the
+          output to work more efficiently */
+       last_i = -1;
+
        if (verbose > 2)
                rprintf(FINFO,"hash search b=%d len=%d\n",s->n,(int)len);
 
@@ -191,6 +195,22 @@ static void hash_search(int f,struct sum_struct *s,
                                false_alarms++;
                                continue;
                        }
+
+                       /* we've found a match, but now check to see
+                           if last_i can hint at a better match */
+                       for (j++; j<s->count && targets[j].t == t; j++) {
+                               int i2 = targets[j].t;
+                               if (i2 == last_i + 1) {
+                                       if (sum != s->sums[i2].sum1) break;
+                                       if (memcmp(sum2,s->sums[i2].sum2,csum_length) != 0) break;
+                                       /* we've found an adjacent match - the RLL coder 
+                                          will be happy */
+                                       i = i2;
+                                       break;
+                               }
+                       }
+
+                       last_i = i;
                        
                        matched(f,s,buf,offset,i);
                        offset += s->sums[i].len - 1;