1 /*
2 * patch-delta.c:
3 * recreate a buffer from a source and the delta produced by diff-delta.c
4 *
5 * (C) 2005 Nicolas Pitre <nico@cam.org>
6 *
7 * This code is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 */
12 #include <stdlib.h>
13 #include <string.h>
14 #include "delta.h"
16 void *patch_delta(void *src_buf, unsigned long src_size,
17 void *delta_buf, unsigned long delta_size,
18 unsigned long *dst_size)
19 {
20 const unsigned char *data, *top;
21 unsigned char *dst_buf, *out, cmd;
22 unsigned long size;
24 if (delta_size < DELTA_SIZE_MIN)
25 return NULL;
27 data = delta_buf;
28 top = delta_buf + delta_size;
30 /* make sure the orig file size matches what we expect */
31 size = get_delta_hdr_size(&data);
32 if (size != src_size)
33 return NULL;
35 /* now the result size */
36 size = get_delta_hdr_size(&data);
37 dst_buf = malloc(size + 1);
38 if (!dst_buf)
39 return NULL;
40 dst_buf[size] = 0;
42 out = dst_buf;
43 while (data < top) {
44 cmd = *data++;
45 if (cmd & 0x80) {
46 unsigned long cp_off = 0, cp_size = 0;
47 const unsigned char *buf;
48 if (cmd & 0x01) cp_off = *data++;
49 if (cmd & 0x02) cp_off |= (*data++ << 8);
50 if (cmd & 0x04) cp_off |= (*data++ << 16);
51 if (cmd & 0x08) cp_off |= (*data++ << 24);
52 if (cmd & 0x10) cp_size = *data++;
53 if (cmd & 0x20) cp_size |= (*data++ << 8);
54 if (cp_size == 0) cp_size = 0x10000;
55 buf = (cmd & 0x40) ? dst_buf : src_buf;
56 memcpy(out, buf + cp_off, cp_size);
57 out += cp_size;
58 } else {
59 memcpy(out, data, cmd);
60 out += cmd;
61 data += cmd;
62 }
63 }
65 /* sanity check */
66 if (data != top || out - dst_buf != size) {
67 free(dst_buf);
68 return NULL;
69 }
71 *dst_size = size;
72 return dst_buf;
73 }