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a310d434 NP |
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(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; | |
23 | int i; | |
24 | ||
25 | /* the smallest delta size possible is 6 bytes */ | |
26 | if (delta_size < 6) | |
27 | return NULL; | |
28 | ||
29 | data = delta_buf; | |
30 | top = delta_buf + delta_size; | |
31 | ||
32 | /* make sure the orig file size matches what we expect */ | |
33 | size = i = 0; | |
34 | cmd = *data++; | |
35 | while (cmd) { | |
36 | if (cmd & 1) | |
37 | size |= *data++ << i; | |
38 | i += 8; | |
39 | cmd >>= 1; | |
40 | } | |
41 | if (size != src_size) | |
42 | return NULL; | |
43 | ||
44 | /* now the result size */ | |
45 | size = i = 0; | |
46 | cmd = *data++; | |
47 | while (cmd) { | |
48 | if (cmd & 1) | |
49 | size |= *data++ << i; | |
50 | i += 8; | |
51 | cmd >>= 1; | |
52 | } | |
53 | dst_buf = malloc(size); | |
54 | if (!dst_buf) | |
55 | return NULL; | |
56 | ||
57 | out = dst_buf; | |
58 | while (data < top) { | |
59 | cmd = *data++; | |
60 | if (cmd & 0x80) { | |
61 | unsigned long cp_off = 0, cp_size = 0; | |
62 | const unsigned char *buf; | |
63 | if (cmd & 0x01) cp_off = *data++; | |
64 | if (cmd & 0x02) cp_off |= (*data++ << 8); | |
65 | if (cmd & 0x04) cp_off |= (*data++ << 16); | |
66 | if (cmd & 0x08) cp_off |= (*data++ << 24); | |
67 | if (cmd & 0x10) cp_size = *data++; | |
68 | if (cmd & 0x20) cp_size |= (*data++ << 8); | |
69 | if (cp_size == 0) cp_size = 0x10000; | |
70 | buf = (cmd & 0x40) ? dst_buf : src_buf; | |
71 | memcpy(out, buf + cp_off, cp_size); | |
72 | out += cp_size; | |
73 | } else { | |
74 | memcpy(out, data, cmd); | |
75 | out += cmd; | |
76 | data += cmd; | |
77 | } | |
78 | } | |
79 | ||
80 | /* sanity check */ | |
81 | if (data != top || out - dst_buf != size) { | |
82 | free(dst_buf); | |
83 | return NULL; | |
84 | } | |
85 | ||
86 | *dst_size = size; | |
87 | return dst_buf; | |
88 | } |