X-Git-Url: https://git.octo.it/?a=blobdiff_plain;f=count-delta.c;h=058a2aadb1475801ea7573837867fa79bf1766c1;hb=bdaa085f8c33e75cf477ff6b4292f35c9c5f4c22;hp=3bcc205f5131a168ac71d9b011d11920e25736f8;hpb=844e6e4d58d3e52eee7fb490bfaeadaa5ea2d59c;p=git.git

diff --git a/count-delta.c b/count-delta.c
index 3bcc205f..058a2aad 100644
--- 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 */
@@ -83,10 +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.
 	 */
-	return (src_size - copied_from_source) + added_literal;
+	*src_copied = copied_from_source;
+	*literal_added = added_literal;
+	return 0;
 }