pack-objects: reuse data from existing packs.

diff --git a/count-delta.c b/count-delta.c
index e10c832a758f49e9117a3456686d54f8b94ce10b..058a2aadb1475801ea7573837867fa79bf1766c1 100644 (file)
--- a/count-delta.c
+++ b/count-delta.c
@@ -6,53 +6,34 @@
 #include <stdlib.h>
 #include <string.h>
 #include <limits.h>
+#include "delta.h"
 #include "count-delta.h"
 
-static unsigned long get_hdr_size(const unsigned char **datap)
-{
-       const unsigned char *data = *datap;
-       unsigned long size;
-       unsigned char cmd;
-       int i;
-       size = i = 0;
-       cmd = *data++;
-       while (cmd) {
-               if (cmd & 1)
-                       size |= *data++ << i;
-               i += 8;
-               cmd >>= 1;
-       }
-       *datap = data;
-       return size;
-}
-
 /*
  * NOTE.  We do not _interpret_ delta fully.  As an approximation, we
  * just count the number of bytes that are copied from the source, and
- * the number of literal data bytes that are inserted.  Number of
- * bytes that are _not_ copied from the source is deletion, and number
- * of inserted literal bytes are addition, so sum of them is what we
- * return.  xdelta can express an edit that copies data inside of the
- * destination which originally came from the source.  We do not count
- * that in the following routine, so we are undercounting the source
- * material that remains in the final output that way.
+ * the number of literal data bytes that are inserted.
+ *
+ * Number of bytes that are _not_ copied from the source is deletion,
+ * and number of inserted literal bytes are addition, so sum of them
+ * is the extent of damage.
  */
-unsigned long count_delta(void *delta_buf, unsigned long delta_size)
+int count_delta(void *delta_buf, unsigned long delta_size,
+               unsigned long *src_copied, unsigned long *literal_added)
 {
        unsigned long copied_from_source, added_literal;
        const unsigned char *data, *top;
        unsigned char cmd;
        unsigned long src_size, dst_size, out;
 
-       /* the smallest delta size possible is 6 bytes */
-       if (delta_size < 6)
-               return UINT_MAX;
+       if (delta_size < DELTA_SIZE_MIN)
+               return -1;
 
        data = delta_buf;
        top = delta_buf + delta_size;
 
-       src_size = get_hdr_size(&data);
-       dst_size = get_hdr_size(&data);
+       src_size = get_delta_hdr_size(&data);
+       dst_size = get_delta_hdr_size(&data);
 
        added_literal = copied_from_source = out = 0;
        while (data < top) {
@@ -65,13 +46,10 @@ unsigned long count_delta(void *delta_buf, unsigned long delta_size)
                        if (cmd & 0x08) cp_off |= (*data++ << 24);
                        if (cmd & 0x10) cp_size = *data++;
                        if (cmd & 0x20) cp_size |= (*data++ << 8);
+                       if (cmd & 0x40) cp_size |= (*data++ << 16);
                        if (cp_size == 0) cp_size = 0x10000;
 
-                       if (cmd & 0x40)
-                               /* copy from dst */
-                               ;
-                       else
-                               copied_from_source += cp_size;
+                       copied_from_source += cp_size;
                        out += cp_size;
                } else {
                        /* write literal into dst */
@@ -83,13 +61,12 @@ unsigned long count_delta(void *delta_buf, unsigned long delta_size)
 
        /* sanity check */
        if (data != top || out != dst_size)
-               return UINT_MAX;
+               return -1;
 
        /* delete size is what was _not_ copied from source.
         * edit size is that and literal additions.
         */
-       if (src_size + added_literal < copied_from_source)
-               /* we ended up overcounting and underflowed */
-               return 0;
-       return (src_size - copied_from_source) + added_literal;
+       *src_copied = copied_from_source;
+       *literal_added = added_literal;
+       return 0;
 }