xref: /third_party/ffmpeg/libavcodec/snappy.c (revision cabdff1a) 
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
25enum {
26    SNAPPY_LITERAL,
27    SNAPPY_COPY_1,
28    SNAPPY_COPY_2,
29    SNAPPY_COPY_4,
30};
31
32static 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
49static 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
78static 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
94static 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
103static 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
112static 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
121static 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
131int64_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
141int 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