t7610-mergetool: use test_cmp instead of test $(cat file) = $txt
[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@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 #define PARSE_CP_PARAM(bit, var, shift) do { \
44                         if (cmd & (bit)) { \
45                                 if (data >= top) \
46                                         goto bad_length; \
47                                 var |= ((unsigned) *data++ << (shift)); \
48                         } } while (0)
49                         PARSE_CP_PARAM(0x01, cp_off, 0);
50                         PARSE_CP_PARAM(0x02, cp_off, 8);
51                         PARSE_CP_PARAM(0x04, cp_off, 16);
52                         PARSE_CP_PARAM(0x08, cp_off, 24);
53                         PARSE_CP_PARAM(0x10, cp_size, 0);
54                         PARSE_CP_PARAM(0x20, cp_size, 8);
55                         PARSE_CP_PARAM(0x40, cp_size, 16);
56 #undef PARSE_CP_PARAM
57                         if (cp_size == 0) cp_size = 0x10000;
58                         if (unsigned_add_overflows(cp_off, cp_size) ||
59                             cp_off + cp_size > src_size ||
60                             cp_size > size)
61                                 goto bad_length;
62                         memcpy(out, (char *) src_buf + cp_off, cp_size);
63                         out += cp_size;
64                         size -= cp_size;
65                 } else if (cmd) {
66                         if (cmd > size || cmd > top - data)
67                                 goto bad_length;
68                         memcpy(out, data, cmd);
69                         out += cmd;
70                         data += cmd;
71                         size -= cmd;
72                 } else {
73                         /*
74                          * cmd == 0 is reserved for future encoding
75                          * extensions. In the mean time we must fail when
76                          * encountering them (might be data corruption).
77                          */
78                         error("unexpected delta opcode 0");
79                         goto bad;
80                 }
81         }
82
83         /* sanity check */
84         if (data != top || size != 0) {
85                 bad_length:
86                 error("delta replay has gone wild");
87                 bad:
88                 free(dst_buf);
89                 return NULL;
90         }
91
92         *dst_size = out - dst_buf;
93         return dst_buf;
94 }