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[git/git.git] / patch-delta.c
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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 *
03aa8ff3 5 * (C) 2005 Nicolas Pitre <nico@fluxnic.net>
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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
57b73150 12#include "git-compat-util.h"
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13#include "delta.h"
14
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15void *patch_delta(const void *src_buf, unsigned long src_size,
16 const void *delta_buf, unsigned long delta_size,
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17 unsigned long *dst_size)
18{
19 const unsigned char *data, *top;
20 unsigned char *dst_buf, *out, cmd;
21 unsigned long size;
a310d434 22
dcde55bc 23 if (delta_size < DELTA_SIZE_MIN)
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24 return NULL;
25
26 data = delta_buf;
1d7f171c 27 top = (const unsigned char *) delta_buf + delta_size;
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28
29 /* make sure the orig file size matches what we expect */
8960844a 30 size = get_delta_hdr_size(&data, top);
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31 if (size != src_size)
32 return NULL;
33
34 /* now the result size */
8960844a 35 size = get_delta_hdr_size(&data, top);
57b73150 36 dst_buf = xmalloc(size + 1);
ce726ec8 37 dst_buf[size] = 0;
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38
39 out = dst_buf;
40 while (data < top) {
41 cmd = *data++;
42 if (cmd & 0x80) {
43 unsigned long cp_off = 0, cp_size = 0;
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44 if (cmd & 0x01) cp_off = *data++;
45 if (cmd & 0x02) cp_off |= (*data++ << 8);
46 if (cmd & 0x04) cp_off |= (*data++ << 16);
48fb7deb 47 if (cmd & 0x08) cp_off |= ((unsigned) *data++ << 24);
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48 if (cmd & 0x10) cp_size = *data++;
49 if (cmd & 0x20) cp_size |= (*data++ << 8);
d60fc1c8 50 if (cmd & 0x40) cp_size |= (*data++ << 16);
a310d434 51 if (cp_size == 0) cp_size = 0x10000;
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52 if (cp_off + cp_size < cp_size ||
53 cp_off + cp_size > src_size ||
54 cp_size > size)
57b73150 55 break;
1d7f171c 56 memcpy(out, (char *) src_buf + cp_off, cp_size);
a310d434 57 out += cp_size;
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58 size -= cp_size;
59 } else if (cmd) {
60 if (cmd > size)
57b73150 61 break;
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62 memcpy(out, data, cmd);
63 out += cmd;
64 data += cmd;
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65 size -= cmd;
66 } else {
67 /*
68 * cmd == 0 is reserved for future encoding
69 * extensions. In the mean time we must fail when
70 * encountering them (might be data corruption).
71 */
57b73150 72 error("unexpected delta opcode 0");
8960844a 73 goto bad;
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74 }
75 }
76
77 /* sanity check */
8960844a 78 if (data != top || size != 0) {
57b73150 79 error("delta replay has gone wild");
8960844a 80 bad:
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81 free(dst_buf);
82 return NULL;
83 }
84
8960844a 85 *dst_size = out - dst_buf;
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86 return dst_buf;
87}