libavutil/lzo.c

   1 /*
   2  * LZO 1x decompression
   3  * Copyright (c) 2006 Reimar Doeffinger
   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 <limits.h>
  23 #include <stdint.h>
  24 #include <string.h>
  25
  26 #include "avassert.h"
  27 #include "intreadwrite.h"
  28 #include "lzo.h"
  29 #include "macros.h"
  30 #include "mem.h"
  31
  32 /// Define if we may write up to 12 bytes beyond the output buffer.
  33 #define OUTBUF_PADDED 1
  34 /// Define if we may read up to 8 bytes beyond the input buffer.
  35 #define INBUF_PADDED 1
  36
  37 typedef struct LZOContext {
  38     const uint8_t *in, *in_end;
  39     uint8_t *out_start, *out, *out_end;
  40     int error;
  41 } LZOContext;
  42
  43 /**
  44  * @brief Reads one byte from the input buffer, avoiding an overrun.
  45  * @return byte read
  46  */
  47 static inline int get_byte(LZOContext *c)
  48 {
  49     if (c->in < c->in_end)
  50         return *c->in++;
  51     c->error |= AV_LZO_INPUT_DEPLETED;
  52     return 1;
  53 }
  54
  55 #ifdef INBUF_PADDED
  56 #define GETB(c) (*(c).in++)
  57 #else
  58 #define GETB(c) get_byte(&(c))
  59 #endif
  60
  61 /**
  62  * @brief Decodes a length value in the coding used by lzo.
  63  * @param x previous byte value
  64  * @param mask bits used from x
  65  * @return decoded length value
  66  */
  67 static inline int get_len(LZOContext *c, int x, int mask)
  68 {
  69     int cnt = x & mask;
  70     if (!cnt) {
  71         while (!(x = get_byte(c))) {
  72             if (cnt >= INT_MAX - 1000) {
  73                 c->error |= AV_LZO_ERROR;
  74                 break;
  75             }
  76             cnt += 255;
  77         }
  78         cnt += mask + x;
  79     }
  80     return cnt;
  81 }
  82
  83 /**
  84  * @brief Copies bytes from input to output buffer with checking.
  85  * @param cnt number of bytes to copy, must be >= 0
  86  */
  87 static inline void copy(LZOContext *c, int cnt)
  88 {
  89     register const uint8_t *src = c->in;
  90     register uint8_t *dst       = c->out;
  91     av_assert0(cnt >= 0);
  92     if (cnt > c->in_end - src) {
  93         cnt       = FFMAX(c->in_end - src, 0);
  94         c->error |= AV_LZO_INPUT_DEPLETED;
  95     }
  96     if (cnt > c->out_end - dst) {
  97         cnt       = FFMAX(c->out_end - dst, 0);
  98         c->error |= AV_LZO_OUTPUT_FULL;
  99     }
 100 #if defined(INBUF_PADDED) && defined(OUTBUF_PADDED)
 101     AV_COPY32U(dst, src);
 102     src += 4;
 103     dst += 4;
 104     cnt -= 4;
 105     if (cnt > 0)
 106 #endif
 107     memcpy(dst, src, cnt);
 108     c->in  = src + cnt;
 109     c->out = dst + cnt;
 110 }
 111
 112 /**
 113  * @brief Copies previously decoded bytes to current position.
 114  * @param back how many bytes back we start, must be > 0
 115  * @param cnt number of bytes to copy, must be > 0
 116  *
 117  * cnt > back is valid, this will copy the bytes we just copied,
 118  * thus creating a repeating pattern with a period length of back.
 119  */
 120 static inline void copy_backptr(LZOContext *c, int back, int cnt)
 121 {
 122     register uint8_t *dst       = c->out;
 123     av_assert0(cnt > 0);
 124     if (dst - c->out_start < back) {
 125         c->error |= AV_LZO_INVALID_BACKPTR;
 126         return;
 127     }
 128     if (cnt > c->out_end - dst) {
 129         cnt       = FFMAX(c->out_end - dst, 0);
 130         c->error |= AV_LZO_OUTPUT_FULL;
 131     }
 132     av_memcpy_backptr(dst, back, cnt);
 133     c->out = dst + cnt;
 134 }
 135
 136 int av_lzo1x_decode(void *out, int *outlen, const void *in, int *inlen)
 137 {
 138     int state = 0;
 139     int x;
 140     LZOContext c;
 141     if (*outlen <= 0 || *inlen <= 0) {
 142         int res = 0;
 143         if (*outlen <= 0)
 144             res |= AV_LZO_OUTPUT_FULL;
 145         if (*inlen <= 0)
 146             res |= AV_LZO_INPUT_DEPLETED;
 147         return res;
 148     }
 149     c.in      = in;
 150     c.in_end  = (const uint8_t *)in + *inlen;
 151     c.out     = c.out_start = out;
 152     c.out_end = (uint8_t *)out + *outlen;
 153     c.error   = 0;
 154     x         = GETB(c);
 155     if (x > 17) {
 156         copy(&c, x - 17);
 157         x = GETB(c);
 158         if (x < 16)
 159             c.error |= AV_LZO_ERROR;
 160     }
 161     if (c.in > c.in_end)
 162         c.error |= AV_LZO_INPUT_DEPLETED;
 163     while (!c.error) {
 164         int cnt, back;
 165         if (x > 15) {
 166             if (x > 63) {
 167                 cnt  = (x >> 5) - 1;
 168                 back = (GETB(c) << 3) + ((x >> 2) & 7) + 1;
 169             } else if (x > 31) {
 170                 cnt  = get_len(&c, x, 31);
 171                 x    = GETB(c);
 172                 back = (GETB(c) << 6) + (x >> 2) + 1;
 173             } else {
 174                 cnt   = get_len(&c, x, 7);
 175                 back  = (1 << 14) + ((x & 8) << 11);
 176                 x     = GETB(c);
 177                 back += (GETB(c) << 6) + (x >> 2);
 178                 if (back == (1 << 14)) {
 179                     if (cnt != 1)
 180                         c.error |= AV_LZO_ERROR;
 181                     break;
 182                 }
 183             }
 184         } else if (!state) {
 185             cnt = get_len(&c, x, 15);
 186             copy(&c, cnt + 3);
 187             x = GETB(c);
 188             if (x > 15)
 189                 continue;
 190             cnt  = 1;
 191             back = (1 << 11) + (GETB(c) << 2) + (x >> 2) + 1;
 192         } else {
 193             cnt  = 0;
 194             back = (GETB(c) << 2) + (x >> 2) + 1;
 195         }
 196         copy_backptr(&c, back, cnt + 2);
 197         state =
 198         cnt   = x & 3;
 199         copy(&c, cnt);
 200         x = GETB(c);
 201     }
 202     *inlen = c.in_end - c.in;
 203     if (c.in > c.in_end)
 204         *inlen = 0;
 205     *outlen = c.out_end - c.out;
 206     return c.error;
 207 }