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[git.git] / count-delta.c

diff --git a/count-delta.c b/count-delta.c
index 978a60c..3ee3a0c 100644 (file)
--- a/count-delta.c
+++ b/count-delta.c
@@ -3,11 +3,74 @@
  * 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 "delta.h"
-#include "count-delta.h"
+
+struct span {
+       struct span *next;
+       unsigned long ofs;
+       unsigned long end;
+};
+
+static void touch_range(struct span **span,
+                       unsigned long ofs, unsigned long end)
+{
+       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;
+               }
+       }
+}
+
+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
@@ -16,19 +79,16 @@
  *
  * 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.
+ * is the extent of damage.
  */
 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;
 
        if (delta_size < DELTA_SIZE_MIN)
                return -1;
@@ -39,7 +99,7 @@ int count_delta(void *delta_buf, unsigned long delta_size,
        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) {
@@ -53,7 +113,7 @@ int count_delta(void *delta_buf, unsigned long delta_size,
                        if (cmd & 0x40) cp_size |= (*data++ << 16);
                        if (cp_size == 0) cp_size = 0x10000;
 
-                       copied_from_source += cp_size;
+                       touch_range(&span, cp_off, cp_off+cp_size);
                        out += cp_size;
                } else {
                        /* write literal into dst */
@@ -63,6 +123,8 @@ int count_delta(void *delta_buf, unsigned long delta_size,
                }
        }
 
+       *src_copied = count_range(span);
+
        /* sanity check */
        if (data != top || out != dst_size)
                return -1;
@@ -70,7 +132,6 @@ int count_delta(void *delta_buf, unsigned long delta_size,
        /* delete size is what was _not_ copied from source.
         * edit size is that and literal additions.
         */
-       *src_copied = copied_from_source;
        *literal_added = added_literal;
        return 0;
 }