1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
|
/*
* Copyright (C) the libgit2 contributors. All rights reserved.
*
* This file is part of libgit2, distributed under the GNU GPL v2 with
* a Linking Exception. For full terms see the included COPYING file.
*/
#include "common.h"
#include "git2/odb.h"
#include "delta-apply.h"
/*
* This file was heavily cribbed from BinaryDelta.java in JGit, which
* itself was heavily cribbed from <code>patch-delta.c</code> in the
* GIT project. The original delta patching code was written by
* Nicolas Pitre <nico@cam.org>.
*/
static int hdr_sz(
size_t *size,
const unsigned char **delta,
const unsigned char *end)
{
const unsigned char *d = *delta;
size_t r = 0;
unsigned int c, shift = 0;
do {
if (d == end)
return -1;
c = *d++;
r |= (c & 0x7f) << shift;
shift += 7;
} while (c & 0x80);
*delta = d;
*size = r;
return 0;
}
int git__delta_read_header(
const unsigned char *delta,
size_t delta_len,
size_t *base_sz,
size_t *res_sz)
{
const unsigned char *delta_end = delta + delta_len;
if ((hdr_sz(base_sz, &delta, delta_end) < 0) ||
(hdr_sz(res_sz, &delta, delta_end) < 0))
return -1;
return 0;
}
int git__delta_apply(
git_rawobj *out,
const unsigned char *base,
size_t base_len,
const unsigned char *delta,
size_t delta_len)
{
const unsigned char *delta_end = delta + delta_len;
size_t base_sz, res_sz, alloc_sz;
unsigned char *res_dp;
/* Check that the base size matches the data we were given;
* if not we would underflow while accessing data from the
* base object, resulting in data corruption or segfault.
*/
if ((hdr_sz(&base_sz, &delta, delta_end) < 0) || (base_sz != base_len)) {
giterr_set(GITERR_INVALID, "Failed to apply delta. Base size does not match given data");
return -1;
}
if (hdr_sz(&res_sz, &delta, delta_end) < 0) {
giterr_set(GITERR_INVALID, "Failed to apply delta. Base size does not match given data");
return -1;
}
GITERR_CHECK_ALLOC_ADD(&alloc_sz, res_sz, 1);
res_dp = git__malloc(alloc_sz);
GITERR_CHECK_ALLOC(res_dp);
res_dp[res_sz] = '\0';
out->data = res_dp;
out->len = res_sz;
while (delta < delta_end) {
unsigned char cmd = *delta++;
if (cmd & 0x80) {
/* cmd is a copy instruction; copy from the base.
*/
size_t off = 0, len = 0;
if (cmd & 0x01) off = *delta++;
if (cmd & 0x02) off |= *delta++ << 8;
if (cmd & 0x04) off |= *delta++ << 16;
if (cmd & 0x08) off |= *delta++ << 24;
if (cmd & 0x10) len = *delta++;
if (cmd & 0x20) len |= *delta++ << 8;
if (cmd & 0x40) len |= *delta++ << 16;
if (!len) len = 0x10000;
if (base_len < off + len || res_sz < len)
goto fail;
memcpy(res_dp, base + off, len);
res_dp += len;
res_sz -= len;
} else if (cmd) {
/* cmd is a literal insert instruction; copy from
* the delta stream itself.
*/
if (delta_end - delta < cmd || res_sz < cmd)
goto fail;
memcpy(res_dp, delta, cmd);
delta += cmd;
res_dp += cmd;
res_sz -= cmd;
} else {
/* cmd == 0 is reserved for future encodings.
*/
goto fail;
}
}
if (delta != delta_end || res_sz)
goto fail;
return 0;
fail:
git__free(out->data);
out->data = NULL;
giterr_set(GITERR_INVALID, "Failed to apply delta");
return -1;
}
|
