libavcodec/snappy.c

   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
  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
  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
  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
  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
 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
 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
 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
 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
 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 }