1 /*
2 * Snappy decompression algorithm
3 * Copyright (c) 2015 Luca Barbato
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22 #include "libavutil/mem.h"
23
24 #include "bytestream.h"
25 #include "snappy.h"
26
27 enum {
28 SNAPPY_LITERAL,
29 SNAPPY_COPY_1,
30 SNAPPY_COPY_2,
31 SNAPPY_COPY_4,
32 };
33
bytestream2_get_levarint(GetByteContext * gb)34 static int64_t bytestream2_get_levarint(GetByteContext *gb)
35 {
36 uint64_t val = 0;
37 int shift = 0;
38 int tmp;
39
40 do {
41 tmp = bytestream2_get_byte(gb);
42 if (shift > 31 || ((tmp & 127LL) << shift) > INT_MAX)
43 return AVERROR_INVALIDDATA;
44 val |= (tmp & 127) << shift;
45 shift += 7;
46 } while (tmp & 128);
47
48 return val;
49 }
50
snappy_literal(GetByteContext * gb,uint8_t * p,int size,int val)51 static int snappy_literal(GetByteContext *gb, uint8_t *p, int size, int val)
52 {
53 unsigned int len = 1;
54
55 switch (val) {
56 case 63:
57 len += bytestream2_get_le32(gb);
58 break;
59 case 62:
60 len += bytestream2_get_le24(gb);
61 break;
62 case 61:
63 len += bytestream2_get_le16(gb);
64 break;
65 case 60:
66 len += bytestream2_get_byte(gb);
67 break;
68 default: // val < 60
69 len += val;
70 }
71
72 if (size < len)
73 return AVERROR_INVALIDDATA;
74
75 bytestream2_get_buffer(gb, p, len);
76
77 return len;
78 }
79
snappy_copy(uint8_t * start,uint8_t * p,int size,unsigned int off,int len)80 static int snappy_copy(uint8_t *start, uint8_t *p, int size,
81 unsigned int off, int len)
82 {
83 uint8_t *q;
84 int i;
85 if (off > p - start || size < len)
86 return AVERROR_INVALIDDATA;
87
88 q = p - off;
89
90 for (i = 0; i < len; i++)
91 p[i] = q[i];
92
93 return len;
94 }
95
snappy_copy1(GetByteContext * gb,uint8_t * start,uint8_t * p,int size,int val)96 static int snappy_copy1(GetByteContext *gb, uint8_t *start, uint8_t *p,
97 int size, int val)
98 {
99 int len = 4 + (val & 0x7);
100 unsigned int off = bytestream2_get_byte(gb) | (val & 0x38) << 5;
101
102 return snappy_copy(start, p, size, off, len);
103 }
104
snappy_copy2(GetByteContext * gb,uint8_t * start,uint8_t * p,int size,int val)105 static int snappy_copy2(GetByteContext *gb, uint8_t *start, uint8_t *p,
106 int size, int val)
107 {
108 int len = 1 + val;
109 unsigned int off = bytestream2_get_le16(gb);
110
111 return snappy_copy(start, p, size, off, len);
112 }
113
snappy_copy4(GetByteContext * gb,uint8_t * start,uint8_t * p,int size,int val)114 static int snappy_copy4(GetByteContext *gb, uint8_t *start, uint8_t *p,
115 int size, int val)
116 {
117 int len = 1 + val;
118 unsigned int off = bytestream2_get_le32(gb);
119
120 return snappy_copy(start, p, size, off, len);
121 }
122
decode_len(GetByteContext * gb)123 static int64_t decode_len(GetByteContext *gb)
124 {
125 int64_t len = bytestream2_get_levarint(gb);
126
127 if (len < 0 || len > UINT_MAX)
128 return AVERROR_INVALIDDATA;
129
130 return len;
131 }
132
ff_snappy_peek_uncompressed_length(GetByteContext * gb)133 int64_t ff_snappy_peek_uncompressed_length(GetByteContext *gb)
134 {
135 int pos = bytestream2_get_bytes_left(gb);
136 int64_t len = decode_len(gb);
137
138 bytestream2_seek(gb, -pos, SEEK_END);
139
140 return len;
141 }
142
ff_snappy_uncompress(GetByteContext * gb,uint8_t * buf,int64_t * size)143 int ff_snappy_uncompress(GetByteContext *gb, uint8_t *buf, int64_t *size)
144 {
145 int64_t len = decode_len(gb);
146 int ret = 0;
147 uint8_t *p;
148
149 if (len < 0)
150 return len;
151
152 if (len > *size)
153 return AVERROR_BUFFER_TOO_SMALL;
154
155 *size = len;
156 p = buf;
157
158 while (bytestream2_get_bytes_left(gb) > 0) {
159 uint8_t s = bytestream2_get_byte(gb);
160 int val = s >> 2;
161
162 switch (s & 0x03) {
163 case SNAPPY_LITERAL:
164 ret = snappy_literal(gb, p, len, val);
165 break;
166 case SNAPPY_COPY_1:
167 ret = snappy_copy1(gb, buf, p, len, val);
168 break;
169 case SNAPPY_COPY_2:
170 ret = snappy_copy2(gb, buf, p, len, val);
171 break;
172 case SNAPPY_COPY_4:
173 ret = snappy_copy4(gb, buf, p, len, val);
174 break;
175 }
176
177 if (ret < 0)
178 return ret;
179
180 p += ret;
181 len -= ret;
182 }
183
184 return 0;
185 }
186