Merge branch 'ew/rebase'
[git/git.git] / patch-delta.c
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 */
11
12 #include <stdlib.h>
13 #include <string.h>
14 #include "delta.h"
15
16 void *patch_delta(const void *src_buf, unsigned long src_size,
17 const 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;
23
24 if (delta_size < DELTA_SIZE_MIN)
25 return NULL;
26
27 data = delta_buf;
28 top = (const unsigned char *) delta_buf + delta_size;
29
30 /* make sure the orig file size matches what we expect */
31 size = get_delta_hdr_size(&data, top);
32 if (size != src_size)
33 return NULL;
34
35 /* now the result size */
36 size = get_delta_hdr_size(&data, top);
37 dst_buf = malloc(size + 1);
38 if (!dst_buf)
39 return NULL;
40 dst_buf[size] = 0;
41
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 if (cmd & 0x01) cp_off = *data++;
48 if (cmd & 0x02) cp_off |= (*data++ << 8);
49 if (cmd & 0x04) cp_off |= (*data++ << 16);
50 if (cmd & 0x08) cp_off |= (*data++ << 24);
51 if (cmd & 0x10) cp_size = *data++;
52 if (cmd & 0x20) cp_size |= (*data++ << 8);
53 if (cmd & 0x40) cp_size |= (*data++ << 16);
54 if (cp_size == 0) cp_size = 0x10000;
55 if (cp_off + cp_size < cp_size ||
56 cp_off + cp_size > src_size ||
57 cp_size > size)
58 goto bad;
59 memcpy(out, (char *) src_buf + cp_off, cp_size);
60 out += cp_size;
61 size -= cp_size;
62 } else if (cmd) {
63 if (cmd > size)
64 goto bad;
65 memcpy(out, data, cmd);
66 out += cmd;
67 data += cmd;
68 size -= cmd;
69 } else {
70 /*
71 * cmd == 0 is reserved for future encoding
72 * extensions. In the mean time we must fail when
73 * encountering them (might be data corruption).
74 */
75 goto bad;
76 }
77 }
78
79 /* sanity check */
80 if (data != top || size != 0) {
81 bad:
82 free(dst_buf);
83 return NULL;
84 }
85
86 *dst_size = out - dst_buf;
87 return dst_buf;
88 }