/* * LZO 1x decompression * Copyright (c) 2006 Reimar Doeffinger * * This file is part of FFmpeg. * * FFmpeg is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * FFmpeg is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with FFmpeg; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ #include "common.h" //! avoid e.g. MPlayers fast_memcpy, it slows things down here #undef memcpy #include <string.h> #include "lzo.h" //! define if we may write up to 12 bytes beyond the output buffer #define OUTBUF_PADDED 1 //! define if we may read up to 4 bytes beyond the input buffer #define INBUF_PADDED 1 typedef struct LZOContext { uint8_t *in, *in_end; uint8_t *out_start, *out, *out_end; int error; } LZOContext; /** * \brief read one byte from input buffer, avoiding overrun * \return byte read */ static inline int get_byte(LZOContext *c) { if (c->in < c->in_end) return *c->in++; c->error |= LZO_INPUT_DEPLETED; return 1; } /** * \brief decode a length value in the coding used by lzo * \param x previous byte value * \param mask bits used from x * \return decoded length value */ static inline int get_len(LZOContext *c, int x, int mask) { int cnt = x & mask; if (!cnt) { while (!(x = get_byte(c))) cnt += 255; cnt += mask + x; } return cnt; } /** * \brief copy bytes from input to output buffer with checking * \param cnt number of bytes to copy, must be > 0 */ static inline void copy(LZOContext *c, int cnt) { register uint8_t *src = c->in; register uint8_t *dst = c->out; if (src + cnt > c->in_end) { cnt = c->in_end - src; c->error |= LZO_INPUT_DEPLETED; } if (dst + cnt > c->out_end) { cnt = c->out_end - dst; c->error |= LZO_OUTPUT_FULL; } #if defined(INBUF_PADDED) && defined(OUTBUF_PADDED) dst[0] = src[0]; dst[1] = src[1]; dst[2] = src[2]; dst[3] = src[3]; src += 4; dst += 4; cnt -= 4; if (cnt > 0) #endif memcpy(dst, src, cnt); c->in = src + cnt; c->out = dst + cnt; } /** * \brief copy previously decoded bytes to current position * \param back how many bytes back we start * \param cnt number of bytes to copy, must be > 0 * * cnt > back is valid, this will copy the bytes we just copied, * thus creating a repeating pattern with a period length of back. */ static inline void copy_backptr(LZOContext *c, int back, int cnt) { register uint8_t *src = &c->out[-back]; register uint8_t *dst = c->out; if (src < c->out_start) { c->error |= LZO_INVALID_BACKPTR; return; } if (dst + cnt > c->out_end) { cnt = c->out_end - dst; c->error |= LZO_OUTPUT_FULL; } if (back == 1) { memset(dst, *src, cnt); dst += cnt; } else { #ifdef OUTBUF_PADDED dst[0] = src[0]; dst[1] = src[1]; dst[2] = src[2]; dst[3] = src[3]; src += 4; dst += 4; cnt -= 4; if (cnt > 0) { dst[0] = src[0]; dst[1] = src[1]; dst[2] = src[2]; dst[3] = src[3]; dst[4] = src[4]; dst[5] = src[5]; dst[6] = src[6]; dst[7] = src[7]; src += 8; dst += 8; cnt -= 8; } #endif if (cnt > 0) { int blocklen = back; while (cnt > blocklen) { memcpy(dst, src, blocklen); dst += blocklen; cnt -= blocklen; blocklen <<= 1; } memcpy(dst, src, cnt); } dst += cnt; } c->out = dst; } /** * \brief decode LZO 1x compressed data * \param out output buffer * \param outlen size of output buffer, number of bytes left are returned here * \param in input buffer * \param inlen size of input buffer, number of bytes left are returned here * \return 0 on success, otherwise error flags, see lzo.h * * make sure all buffers are appropriately padded, in must provide * LZO_INPUT_PADDING, out must provide LZO_OUTPUT_PADDING additional bytes */ int lzo1x_decode(void *out, int *outlen, void *in, int *inlen) { enum {COPY, BACKPTR} state = COPY; int x; LZOContext c; c.in = in; c.in_end = (uint8_t *)in + *inlen; c.out = c.out_start = out; c.out_end = (uint8_t *)out + * outlen; c.error = 0; x = get_byte(&c); if (x > 17) { copy(&c, x - 17); x = get_byte(&c); if (x < 16) c.error |= LZO_ERROR; } while (!c.error) { int cnt, back; if (x >> 4) { if (x >> 6) { cnt = (x >> 5) - 1; back = (get_byte(&c) << 3) + ((x >> 2) & 7) + 1; } else if (x >> 5) { cnt = get_len(&c, x, 31); x = get_byte(&c); back = (get_byte(&c) << 6) + (x >> 2) + 1; } else { cnt = get_len(&c, x, 7); back = (1 << 14) + ((x & 8) << 11); x = get_byte(&c); back += (get_byte(&c) << 6) + (x >> 2); if (back == (1 << 14)) { if (cnt != 1) c.error |= LZO_ERROR; break; } } } else switch (state) { case COPY: cnt = get_len(&c, x, 15); copy(&c, cnt + 3); x = get_byte(&c); if (x >> 4) continue; cnt = 1; back = (1 << 11) + (get_byte(&c) << 2) + (x >> 2) + 1; break; case BACKPTR: cnt = 0; back = (get_byte(&c) << 2) + (x >> 2) + 1; break; } copy_backptr(&c, back, cnt + 2); cnt = x & 3; state = cnt ? BACKPTR : COPY; if (cnt) copy(&c, cnt); x = get_byte(&c); } *inlen = c.in_end - c.in; *outlen = c.out_end - c.out; return c.error; }