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 "bytestream.h"
23 #include "snappy.h"
24
25 enum {
26 SNAPPY_LITERAL,
27 SNAPPY_COPY_1,
28 SNAPPY_COPY_2,
29 SNAPPY_COPY_4,
30 };
31
bytestream2_get_levarint(GetByteContext * gb)32 static int64_t bytestream2_get_levarint(GetByteContext *gb)
33 {
34 uint64_t val = 0;
35 int shift = 0;
36 int tmp;
37
38 do {
39 tmp = bytestream2_get_byte(gb);
40 if (shift > 31 || ((tmp & 127LL) << shift) > INT_MAX)
41 return AVERROR_INVALIDDATA;
42 val |= (tmp & 127) << shift;
43 shift += 7;
44 } while (tmp & 128);
45
46 return val;
47 }
48
snappy_literal(GetByteContext * gb,uint8_t * p,int size,int val)49 static int snappy_literal(GetByteContext *gb, uint8_t *p, int size, int val)
50 {
51 unsigned int len = 1;
52
53 switch (val) {
54 case 63:
55 len += bytestream2_get_le32(gb);
56 break;
57 case 62:
58 len += bytestream2_get_le24(gb);
59 break;
60 case 61:
61 len += bytestream2_get_le16(gb);
62 break;
63 case 60:
64 len += bytestream2_get_byte(gb);
65 break;
66 default: // val < 60
67 len += val;
68 }
69
70 if (size < len)
71 return AVERROR_INVALIDDATA;
72
73 bytestream2_get_buffer(gb, p, len);
74
75 return len;
76 }
77
snappy_copy(uint8_t * start,uint8_t * p,int size,unsigned int off,int len)78 static int snappy_copy(uint8_t *start, uint8_t *p, int size,
79 unsigned int off, int len)
80 {
81 uint8_t *q;
82 int i;
83 if (off > p - start || size < len)
84 return AVERROR_INVALIDDATA;
85
86 q = p - off;
87
88 for (i = 0; i < len; i++)
89 p[i] = q[i];
90
91 return len;
92 }
93
snappy_copy1(GetByteContext * gb,uint8_t * start,uint8_t * p,int size,int val)94 static int snappy_copy1(GetByteContext *gb, uint8_t *start, uint8_t *p,
95 int size, int val)
96 {
97 int len = 4 + (val & 0x7);
98 unsigned int off = bytestream2_get_byte(gb) | (val & 0x38) << 5;
99
100 return snappy_copy(start, p, size, off, len);
101 }
102
snappy_copy2(GetByteContext * gb,uint8_t * start,uint8_t * p,int size,int val)103 static int snappy_copy2(GetByteContext *gb, uint8_t *start, uint8_t *p,
104 int size, int val)
105 {
106 int len = 1 + val;
107 unsigned int off = bytestream2_get_le16(gb);
108
109 return snappy_copy(start, p, size, off, len);
110 }
111
snappy_copy4(GetByteContext * gb,uint8_t * start,uint8_t * p,int size,int val)112 static int snappy_copy4(GetByteContext *gb, uint8_t *start, uint8_t *p,
113 int size, int val)
114 {
115 int len = 1 + val;
116 unsigned int off = bytestream2_get_le32(gb);
117
118 return snappy_copy(start, p, size, off, len);
119 }
120
decode_len(GetByteContext * gb)121 static int64_t decode_len(GetByteContext *gb)
122 {
123 int64_t len = bytestream2_get_levarint(gb);
124
125 if (len < 0 || len > UINT_MAX)
126 return AVERROR_INVALIDDATA;
127
128 return len;
129 }
130
ff_snappy_peek_uncompressed_length(GetByteContext * gb)131 int64_t ff_snappy_peek_uncompressed_length(GetByteContext *gb)
132 {
133 int pos = bytestream2_get_bytes_left(gb);
134 int64_t len = decode_len(gb);
135
136 bytestream2_seek(gb, -pos, SEEK_END);
137
138 return len;
139 }
140
ff_snappy_uncompress(GetByteContext * gb,uint8_t * buf,int64_t * size)141 int ff_snappy_uncompress(GetByteContext *gb, uint8_t *buf, int64_t *size)
142 {
143 int64_t len = decode_len(gb);
144 int ret = 0;
145 uint8_t *p;
146
147 if (len < 0)
148 return len;
149
150 if (len > *size)
151 return AVERROR_BUFFER_TOO_SMALL;
152
153 *size = len;
154 p = buf;
155
156 while (bytestream2_get_bytes_left(gb) > 0) {
157 uint8_t s = bytestream2_get_byte(gb);
158 int val = s >> 2;
159
160 switch (s & 0x03) {
161 case SNAPPY_LITERAL:
162 ret = snappy_literal(gb, p, len, val);
163 break;
164 case SNAPPY_COPY_1:
165 ret = snappy_copy1(gb, buf, p, len, val);
166 break;
167 case SNAPPY_COPY_2:
168 ret = snappy_copy2(gb, buf, p, len, val);
169 break;
170 case SNAPPY_COPY_4:
171 ret = snappy_copy4(gb, buf, p, len, val);
172 break;
173 }
174
175 if (ret < 0)
176 return ret;
177
178 p += ret;
179 len -= ret;
180 }
181
182 return 0;
183 }
184