[PATCH] Tweak count-delta interface

Make it return copied source and insertion separately, so that
later implementation of heuristics can use them more flexibly.

This does not change the heuristics implemented in
diffcore-rename nor diffcore-break in any way.

Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 16 insertions, 14 deletions

diff --git a/count-delta.c b/count-delta.c
index e10c832a7..c7f376788 100644
--- a/count-delta.c
+++ b/count-delta.c
@@ -29,15 +29,18 @@ static unsigned long get_hdr_size(const unsigned char **datap)
 /*
  * 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.  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.
  */
-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;
@@ -46,7 +49,7 @@ unsigned long count_delta(void *delta_buf, unsigned long delta_size)
 
 	/* the smallest delta size possible is 6 bytes */
 	if (delta_size < 6)
-		return UINT_MAX;
+		return -1;
 
 	data = delta_buf;
 	top = delta_buf + delta_size;
@@ -83,13 +86,12 @@ 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;
 }