diff options
Diffstat (limited to 'libavcodec/lzo.c')
| -rw-r--r-- | libavcodec/lzo.c | 167 |
1 files changed, 167 insertions, 0 deletions
diff --git a/libavcodec/lzo.c b/libavcodec/lzo.c new file mode 100644 index 0000000000..a123abb497 --- /dev/null +++ b/libavcodec/lzo.c @@ -0,0 +1,167 @@ +/* + * LZO 1x decompression + * Copyright (c) 2006 Reimar Doeffinger + * + * This library 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 of the License, or (at your option) any later version. + * + * This library 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 this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ +#include "common.h" +#include "lzo.h" + +typedef struct LZOContext { + uint8_t *in, *in_end; + uint8_t *out, *out_end; + int out_size; + 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) { + if (c->in + cnt > c->in_end) { + cnt = c->in_end - c->in; + c->error |= LZO_INPUT_DEPLETED; + } + if (c->out + cnt > c->out_end) { + cnt = c->out_end - c->out; + c->error |= LZO_OUTPUT_FULL; + } + do { + *c->out++ = *c->in++; + } while (--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. + */ +static inline void copy_backptr(LZOContext *c, int back, int cnt) { + if (c->out - back < c->out_end - c->out_size) { + c->error |= LZO_INVALID_BACKPTR; + return; + } + if (c->out + cnt > c->out_end) { + cnt = c->out_end - c->out; + c->error |= LZO_OUTPUT_FULL; + } + do { + *c->out++ = c->out[-back]; + } while (--cnt); +} + +/** + * \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 + */ +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 = in + *inlen; + c.out = out; + c.out_end = out + * outlen; + c.out_size = *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) { + state = BACKPTR; + 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; + if (cnt) + copy(&c, cnt); + else + state = (state == COPY) ? BACKPTR : COPY; + x = get_byte(&c); + } + *inlen = c.in_end - c.in; + *outlen = c.out_end - c.out; + return c.error; +} |