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-rw-r--r--patch-delta.c88
1 files changed, 88 insertions, 0 deletions
diff --git a/patch-delta.c b/patch-delta.c
new file mode 100644
index 0000000000..a8d75ee1c8
--- /dev/null
+++ b/patch-delta.c
@@ -0,0 +1,88 @@
+/*
+ * patch-delta.c:
+ * recreate a buffer from a source and the delta produced by diff-delta.c
+ *
+ * (C) 2005 Nicolas Pitre <nico@cam.org>
+ *
+ * This code is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include "delta.h"
+
+void *patch_delta(void *src_buf, unsigned long src_size,
+ void *delta_buf, unsigned long delta_size,
+ unsigned long *dst_size)
+{
+ const unsigned char *data, *top;
+ unsigned char *dst_buf, *out, cmd;
+ unsigned long size;
+ int i;
+
+ /* the smallest delta size possible is 6 bytes */
+ if (delta_size < 6)
+ return NULL;
+
+ data = delta_buf;
+ top = delta_buf + delta_size;
+
+ /* make sure the orig file size matches what we expect */
+ size = i = 0;
+ cmd = *data++;
+ while (cmd) {
+ if (cmd & 1)
+ size |= *data++ << i;
+ i += 8;
+ cmd >>= 1;
+ }
+ if (size != src_size)
+ return NULL;
+
+ /* now the result size */
+ size = i = 0;
+ cmd = *data++;
+ while (cmd) {
+ if (cmd & 1)
+ size |= *data++ << i;
+ i += 8;
+ cmd >>= 1;
+ }
+ dst_buf = malloc(size);
+ if (!dst_buf)
+ return NULL;
+
+ out = dst_buf;
+ while (data < top) {
+ cmd = *data++;
+ if (cmd & 0x80) {
+ unsigned long cp_off = 0, cp_size = 0;
+ const unsigned char *buf;
+ if (cmd & 0x01) cp_off = *data++;
+ if (cmd & 0x02) cp_off |= (*data++ << 8);
+ if (cmd & 0x04) cp_off |= (*data++ << 16);
+ if (cmd & 0x08) cp_off |= (*data++ << 24);
+ if (cmd & 0x10) cp_size = *data++;
+ if (cmd & 0x20) cp_size |= (*data++ << 8);
+ if (cp_size == 0) cp_size = 0x10000;
+ buf = (cmd & 0x40) ? dst_buf : src_buf;
+ memcpy(out, buf + cp_off, cp_size);
+ out += cp_size;
+ } else {
+ memcpy(out, data, cmd);
+ out += cmd;
+ data += cmd;
+ }
+ }
+
+ /* sanity check */
+ if (data != top || out - dst_buf != size) {
+ free(dst_buf);
+ return NULL;
+ }
+
+ *dst_size = size;
+ return dst_buf;
+}