#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) {
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 */
/* 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;
}