/* * LZO 1x decompression * Copyright (c) 2006 Reimar Doeffinger * * This file is part of Libav. * * Libav 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. * * Libav 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 Libav; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ #include <string.h> #include "avutil.h" #include "common.h" #include "intreadwrite.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 8 bytes beyond the input buffer. #define INBUF_PADDED 1 typedef struct LZOContext { const uint8_t *in, *in_end; uint8_t *out_start, *out, *out_end; int error; } LZOContext; /** * @brief Reads one byte from the input buffer, avoiding an overrun. * @return byte read */ static inline int get_byte(LZOContext *c) { if (c->in < c->in_end) return *c->in++; c->error |= AV_LZO_INPUT_DEPLETED; return 1; } #ifdef INBUF_PADDED #define GETB(c) (*(c).in++) #else #define GETB(c) get_byte(&(c)) #endif /** * @brief Decodes 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 Copies 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 const uint8_t *src = c->in; register uint8_t *dst = c->out; if (cnt > c->in_end - src) { cnt = FFMAX(c->in_end - src, 0); c->error |= AV_LZO_INPUT_DEPLETED; } if (cnt > c->out_end - dst) { cnt = FFMAX(c->out_end - dst, 0); c->error |= AV_LZO_OUTPUT_FULL; } #if defined(INBUF_PADDED) && defined(OUTBUF_PADDED) AV_COPY32U(dst, src); src += 4; dst += 4; cnt -= 4; if (cnt > 0) #endif memcpy(dst, src, cnt); c->in = src + cnt; c->out = dst + cnt; } /** * @brief Copies 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 *dst = c->out; if (dst - c->out_start < back) { c->error |= AV_LZO_INVALID_BACKPTR; return; } if (cnt > c->out_end - dst) { cnt = FFMAX(c->out_end - dst, 0); c->error |= AV_LZO_OUTPUT_FULL; } av_memcpy_backptr(dst, back, cnt); c->out = dst + cnt; } int av_lzo1x_decode(void *out, int *outlen, const void *in, int *inlen) { int state = 0; int x; LZOContext c; if (!*outlen || !*inlen) { int res = 0; if (!*outlen) res |= AV_LZO_OUTPUT_FULL; if (!*inlen) res |= AV_LZO_INPUT_DEPLETED; return res; } c.in = in; c.in_end = (const uint8_t *)in + *inlen; c.out = c.out_start = out; c.out_end = (uint8_t *)out + *outlen; c.error = 0; x = GETB(c); if (x > 17) { copy(&c, x - 17); x = GETB(c); if (x < 16) c.error |= AV_LZO_ERROR; } if (c.in > c.in_end) c.error |= AV_LZO_INPUT_DEPLETED; while (!c.error) { int cnt, back; if (x > 15) { if (x > 63) { cnt = (x >> 5) - 1; back = (GETB(c) << 3) + ((x >> 2) & 7) + 1; } else if (x > 31) { cnt = get_len(&c, x, 31); x = GETB(c); back = (GETB(c) << 6) + (x >> 2) + 1; } else { cnt = get_len(&c, x, 7); back = (1 << 14) + ((x & 8) << 11); x = GETB(c); back += (GETB(c) << 6) + (x >> 2); if (back == (1 << 14)) { if (cnt != 1) c.error |= AV_LZO_ERROR; break; } } } else if (!state) { cnt = get_len(&c, x, 15); copy(&c, cnt + 3); x = GETB(c); if (x > 15) continue; cnt = 1; back = (1 << 11) + (GETB(c) << 2) + (x >> 2) + 1; } else { cnt = 0; back = (GETB(c) << 2) + (x >> 2) + 1; } copy_backptr(&c, back, cnt + 2); state = cnt = x & 3; copy(&c, cnt); x = GETB(c); } *inlen = c.in_end - c.in; if (c.in > c.in_end) *inlen = 0; *outlen = c.out_end - c.out; return c.error; }