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/libavutil/lzo.c

http://github.com/FFmpeg/FFmpeg
C | 205 lines | 151 code | 10 blank | 44 comment | 32 complexity | d789bc0e256350a4ebf1e5355c27d1bb MD5 | raw file
  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 <string.h>
 23
 24#include "avutil.h"
 25#include "avassert.h"
 26#include "common.h"
 27#include "intreadwrite.h"
 28#include "lzo.h"
 29
 30/// Define if we may write up to 12 bytes beyond the output buffer.
 31#define OUTBUF_PADDED 1
 32/// Define if we may read up to 8 bytes beyond the input buffer.
 33#define INBUF_PADDED 1
 34
 35typedef struct LZOContext {
 36    const uint8_t *in, *in_end;
 37    uint8_t *out_start, *out, *out_end;
 38    int error;
 39} LZOContext;
 40
 41/**
 42 * @brief Reads one byte from the input buffer, avoiding an overrun.
 43 * @return byte read
 44 */
 45static inline int get_byte(LZOContext *c)
 46{
 47    if (c->in < c->in_end)
 48        return *c->in++;
 49    c->error |= AV_LZO_INPUT_DEPLETED;
 50    return 1;
 51}
 52
 53#ifdef INBUF_PADDED
 54#define GETB(c) (*(c).in++)
 55#else
 56#define GETB(c) get_byte(&(c))
 57#endif
 58
 59/**
 60 * @brief Decodes a length value in the coding used by lzo.
 61 * @param x previous byte value
 62 * @param mask bits used from x
 63 * @return decoded length value
 64 */
 65static inline int get_len(LZOContext *c, int x, int mask)
 66{
 67    int cnt = x & mask;
 68    if (!cnt) {
 69        while (!(x = get_byte(c))) {
 70            if (cnt >= INT_MAX - 1000) {
 71                c->error |= AV_LZO_ERROR;
 72                break;
 73            }
 74            cnt += 255;
 75        }
 76        cnt += mask + x;
 77    }
 78    return cnt;
 79}
 80
 81/**
 82 * @brief Copies bytes from input to output buffer with checking.
 83 * @param cnt number of bytes to copy, must be >= 0
 84 */
 85static inline void copy(LZOContext *c, int cnt)
 86{
 87    register const uint8_t *src = c->in;
 88    register uint8_t *dst       = c->out;
 89    av_assert0(cnt >= 0);
 90    if (cnt > c->in_end - src) {
 91        cnt       = FFMAX(c->in_end - src, 0);
 92        c->error |= AV_LZO_INPUT_DEPLETED;
 93    }
 94    if (cnt > c->out_end - dst) {
 95        cnt       = FFMAX(c->out_end - dst, 0);
 96        c->error |= AV_LZO_OUTPUT_FULL;
 97    }
 98#if defined(INBUF_PADDED) && defined(OUTBUF_PADDED)
 99    AV_COPY32U(dst, src);
100    src += 4;
101    dst += 4;
102    cnt -= 4;
103    if (cnt > 0)
104#endif
105    memcpy(dst, src, cnt);
106    c->in  = src + cnt;
107    c->out = dst + cnt;
108}
109
110/**
111 * @brief Copies previously decoded bytes to current position.
112 * @param back how many bytes back we start, must be > 0
113 * @param cnt number of bytes to copy, must be > 0
114 *
115 * cnt > back is valid, this will copy the bytes we just copied,
116 * thus creating a repeating pattern with a period length of back.
117 */
118static inline void copy_backptr(LZOContext *c, int back, int cnt)
119{
120    register uint8_t *dst       = c->out;
121    av_assert0(cnt > 0);
122    if (dst - c->out_start < back) {
123        c->error |= AV_LZO_INVALID_BACKPTR;
124        return;
125    }
126    if (cnt > c->out_end - dst) {
127        cnt       = FFMAX(c->out_end - dst, 0);
128        c->error |= AV_LZO_OUTPUT_FULL;
129    }
130    av_memcpy_backptr(dst, back, cnt);
131    c->out = dst + cnt;
132}
133
134int av_lzo1x_decode(void *out, int *outlen, const void *in, int *inlen)
135{
136    int state = 0;
137    int x;
138    LZOContext c;
139    if (*outlen <= 0 || *inlen <= 0) {
140        int res = 0;
141        if (*outlen <= 0)
142            res |= AV_LZO_OUTPUT_FULL;
143        if (*inlen <= 0)
144            res |= AV_LZO_INPUT_DEPLETED;
145        return res;
146    }
147    c.in      = in;
148    c.in_end  = (const uint8_t *)in + *inlen;
149    c.out     = c.out_start = out;
150    c.out_end = (uint8_t *)out + *outlen;
151    c.error   = 0;
152    x         = GETB(c);
153    if (x > 17) {
154        copy(&c, x - 17);
155        x = GETB(c);
156        if (x < 16)
157            c.error |= AV_LZO_ERROR;
158    }
159    if (c.in > c.in_end)
160        c.error |= AV_LZO_INPUT_DEPLETED;
161    while (!c.error) {
162        int cnt, back;
163        if (x > 15) {
164            if (x > 63) {
165                cnt  = (x >> 5) - 1;
166                back = (GETB(c) << 3) + ((x >> 2) & 7) + 1;
167            } else if (x > 31) {
168                cnt  = get_len(&c, x, 31);
169                x    = GETB(c);
170                back = (GETB(c) << 6) + (x >> 2) + 1;
171            } else {
172                cnt   = get_len(&c, x, 7);
173                back  = (1 << 14) + ((x & 8) << 11);
174                x     = GETB(c);
175                back += (GETB(c) << 6) + (x >> 2);
176                if (back == (1 << 14)) {
177                    if (cnt != 1)
178                        c.error |= AV_LZO_ERROR;
179                    break;
180                }
181            }
182        } else if (!state) {
183            cnt = get_len(&c, x, 15);
184            copy(&c, cnt + 3);
185            x = GETB(c);
186            if (x > 15)
187                continue;
188            cnt  = 1;
189            back = (1 << 11) + (GETB(c) << 2) + (x >> 2) + 1;
190        } else {
191            cnt  = 0;
192            back = (GETB(c) << 2) + (x >> 2) + 1;
193        }
194        copy_backptr(&c, back, cnt + 2);
195        state =
196        cnt   = x & 3;
197        copy(&c, cnt);
198        x = GETB(c);
199    }
200    *inlen = c.in_end - c.in;
201    if (c.in > c.in_end)
202        *inlen = 0;
203    *outlen = c.out_end - c.out;
204    return c.error;
205}