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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@fluxnic.net> | |
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 "git-compat-util.h" | |
13 | #include "delta.h" | |
14 | ||
15 | void *patch_delta(const void *src_buf, unsigned long src_size, | |
16 | const void *delta_buf, unsigned long delta_size, | |
17 | unsigned long *dst_size) | |
18 | { | |
19 | const unsigned char *data, *top; | |
20 | unsigned char *dst_buf, *out, cmd; | |
21 | unsigned long size; | |
22 | ||
23 | if (delta_size < DELTA_SIZE_MIN) | |
24 | return NULL; | |
25 | ||
26 | data = delta_buf; | |
27 | top = (const unsigned char *) delta_buf + delta_size; | |
28 | ||
29 | /* make sure the orig file size matches what we expect */ | |
30 | size = get_delta_hdr_size(&data, top); | |
31 | if (size != src_size) | |
32 | return NULL; | |
33 | ||
34 | /* now the result size */ | |
35 | size = get_delta_hdr_size(&data, top); | |
36 | dst_buf = xmallocz(size); | |
37 | ||
38 | out = dst_buf; | |
39 | while (data < top) { | |
40 | cmd = *data++; | |
41 | if (cmd & 0x80) { | |
42 | unsigned long cp_off = 0, cp_size = 0; | |
43 | if (cmd & 0x01) cp_off = *data++; | |
44 | if (cmd & 0x02) cp_off |= (*data++ << 8); | |
45 | if (cmd & 0x04) cp_off |= (*data++ << 16); | |
46 | if (cmd & 0x08) cp_off |= ((unsigned) *data++ << 24); | |
47 | if (cmd & 0x10) cp_size = *data++; | |
48 | if (cmd & 0x20) cp_size |= (*data++ << 8); | |
49 | if (cmd & 0x40) cp_size |= (*data++ << 16); | |
50 | if (cp_size == 0) cp_size = 0x10000; | |
51 | if (unsigned_add_overflows(cp_off, cp_size) || | |
52 | cp_off + cp_size > src_size || | |
53 | cp_size > size) | |
54 | break; | |
55 | memcpy(out, (char *) src_buf + cp_off, cp_size); | |
56 | out += cp_size; | |
57 | size -= cp_size; | |
58 | } else if (cmd) { | |
59 | if (cmd > size) | |
60 | break; | |
61 | memcpy(out, data, cmd); | |
62 | out += cmd; | |
63 | data += cmd; | |
64 | size -= cmd; | |
65 | } else { | |
66 | /* | |
67 | * cmd == 0 is reserved for future encoding | |
68 | * extensions. In the mean time we must fail when | |
69 | * encountering them (might be data corruption). | |
70 | */ | |
71 | error("unexpected delta opcode 0"); | |
72 | goto bad; | |
73 | } | |
74 | } | |
75 | ||
76 | /* sanity check */ | |
77 | if (data != top || size != 0) { | |
78 | error("delta replay has gone wild"); | |
79 | bad: | |
80 | free(dst_buf); | |
81 | return NULL; | |
82 | } | |
83 | ||
84 | *dst_size = out - dst_buf; | |
85 | return dst_buf; | |
86 | } |