* The delta-parsing part is almost straight copy of patch-delta.c
* which is (C) 2005 Nicolas Pitre <nico@cam.org>.
*/
+#include "cache.h"
+#include "delta.h"
+#include "count-delta.h"
#include <stdlib.h>
#include <string.h>
#include <limits.h>
-#include "count-delta.h"
-static unsigned long get_hdr_size(const unsigned char **datap)
+struct span {
+ struct span *next;
+ unsigned long ofs;
+ unsigned long end;
+};
+
+static void touch_range(struct span **span,
+ unsigned long ofs, unsigned long end)
{
- 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;
+ struct span *e = *span;
+ struct span *p = NULL;
+
+ while (e && e->ofs <= ofs) {
+ again:
+ if (ofs < e->end) {
+ while (e->end < end) {
+ if (e->next && e->next->ofs <= end) {
+ e->end = e->next->ofs;
+ e = e->next;
+ }
+ else {
+ e->end = end;
+ return;
+ }
+ }
+ return;
+ }
+ p = e;
+ e = e->next;
+ }
+ if (e && e->ofs <= end) {
+ e->ofs = ofs;
+ goto again;
+ }
+ else {
+ e = xmalloc(sizeof(*e));
+ e->ofs = ofs;
+ e->end = end;
+ if (p) {
+ e->next = p->next;
+ p->next = e;
+ }
+ else {
+ e->next = *span;
+ *span = e;
+ }
}
- *datap = data;
- return size;
+}
+
+static unsigned long count_range(struct span *s)
+{
+ struct span *t;
+ unsigned long sz = 0;
+ while (s) {
+ t = s;
+ sz += s->end - s->ofs;
+ s = s->next;
+ free(t);
+ }
+ return sz;
}
/*
* 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;
+ unsigned long added_literal;
const unsigned char *data, *top;
unsigned char cmd;
unsigned long src_size, dst_size, out;
+ struct span *span = NULL;
- /* 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;
+ added_literal = out = 0;
while (data < top) {
cmd = *data++;
if (cmd & 0x80) {
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;
+ touch_range(&span, cp_off, cp_off+cp_size);
out += cp_size;
} else {
/* write literal into dst */
}
}
+ *src_copied = count_range(span);
+
/* 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;
+ *literal_added = added_literal;
+ return 0;
}