X-Git-Url: https://git.octo.it/?a=blobdiff_plain;f=count-delta.c;h=3ee3a0ccf1b92f3f8838ca2e728bde9f60d1b8e8;hb=6d5e6fff52968443018af56e2966cf5866130a4e;hp=e10c832a758f49e9117a3456686d54f8b94ce10b;hpb=8b7d510fb182ca40bd0f905bb2f5543b0d9549de;p=git.git

diff --git a/count-delta.c b/count-delta.c
index e10c832a..3ee3a0cc 100644
--- a/count-delta.c
+++ b/count-delta.c
@@ -3,58 +3,103 @@
  * 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) {
@@ -65,13 +110,10 @@ 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;
+			touch_range(&span, cp_off, cp_off+cp_size);
 			out += cp_size;
 		} else {
 			/* write literal into dst */
@@ -81,15 +123,15 @@ unsigned long count_delta(void *delta_buf, unsigned long delta_size)
 		}
 	}
 
+	*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;
 }