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Diffstat (limited to 'archival/libunarchive/rangecoder.h')
| -rw-r--r-- | archival/libunarchive/rangecoder.h | 158 |
1 files changed, 158 insertions, 0 deletions
diff --git a/archival/libunarchive/rangecoder.h b/archival/libunarchive/rangecoder.h new file mode 100644 index 0000000..bb41591 --- /dev/null +++ b/archival/libunarchive/rangecoder.h @@ -0,0 +1,158 @@ +/* + * Small range coder implementation for lzma. + * Copyright (C) 2006 Aurelien Jacobs <aurel@gnuage.org> + * + * Based on LzmaDecode.c from the LZMA SDK 4.22 (http://www.7-zip.org/) + * Copyright (c) 1999-2005 Igor Pavlov + * + * This program 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. + * + * This program 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 St, Fifth Floor, Boston, MA 02110-1301 USA + */ + +#include <stdint.h> + +#include "libbb.h" + +#ifndef always_inline +# if defined(__GNUC__) && (__GNUC__ > 3 || __GNUC__ == 3 && __GNUC_MINOR__ >0) +# define always_inline __attribute__((always_inline)) inline +# else +# define always_inline inline +# endif +#endif + +#ifdef CONFIG_FEATURE_LZMA_FAST +# define speed_inline always_inline +#else +# define speed_inline +#endif + + +typedef struct { + int fd; + uint8_t *ptr; + uint8_t *buffer; + uint8_t *buffer_end; + int buffer_size; + uint32_t code; + uint32_t range; + uint32_t bound; +} rc_t; + + +#define RC_TOP_BITS 24 +#define RC_MOVE_BITS 5 +#define RC_MODEL_TOTAL_BITS 11 + + +static speed_inline void rc_read(rc_t * rc) +{ + rc->buffer_size = read(rc->fd, rc->buffer, rc->buffer_size); + if (rc->buffer_size <= 0) + bb_error_msg_and_die("unexpected EOF"); + rc->ptr = rc->buffer; + rc->buffer_end = rc->buffer + rc->buffer_size; +} + +static always_inline void rc_init(rc_t * rc, int fd, int buffer_size) +{ + int i; + + rc->fd = fd; + rc->buffer = malloc(buffer_size); + rc->buffer_size = buffer_size; + rc->buffer_end = rc->buffer + rc->buffer_size; + rc->ptr = rc->buffer_end; + + rc->code = 0; + rc->range = 0xFFFFFFFF; + for (i = 0; i < 5; i++) { + if (rc->ptr >= rc->buffer_end) + rc_read(rc); + rc->code = (rc->code << 8) | *rc->ptr++; + } +} + +static always_inline void rc_free(rc_t * rc) +{ + if (ENABLE_FEATURE_CLEAN_UP) + free(rc->buffer); +} + +static always_inline void rc_normalize(rc_t * rc) +{ + if (rc->range < (1 << RC_TOP_BITS)) { + if (rc->ptr >= rc->buffer_end) + rc_read(rc); + rc->range <<= 8; + rc->code = (rc->code << 8) | *rc->ptr++; + } +} + +static speed_inline int rc_is_bit_0(rc_t * rc, uint16_t * p) +{ + rc_normalize(rc); + rc->bound = *p * (rc->range >> RC_MODEL_TOTAL_BITS); + return rc->code < rc->bound; +} + +static speed_inline void rc_update_bit_0(rc_t * rc, uint16_t * p) +{ + rc->range = rc->bound; + *p += ((1 << RC_MODEL_TOTAL_BITS) - *p) >> RC_MOVE_BITS; +} + +static speed_inline void rc_update_bit_1(rc_t * rc, uint16_t * p) +{ + rc->range -= rc->bound; + rc->code -= rc->bound; + *p -= *p >> RC_MOVE_BITS; +} + +static speed_inline int rc_get_bit(rc_t * rc, uint16_t * p, int *symbol) +{ + if (rc_is_bit_0(rc, p)) { + rc_update_bit_0(rc, p); + *symbol *= 2; + return 0; + } else { + rc_update_bit_1(rc, p); + *symbol = *symbol * 2 + 1; + return 1; + } +} + +static always_inline int rc_direct_bit(rc_t * rc) +{ + rc_normalize(rc); + rc->range >>= 1; + if (rc->code >= rc->range) { + rc->code -= rc->range; + return 1; + } + return 0; +} + +static speed_inline void +rc_bit_tree_decode(rc_t * rc, uint16_t * p, int num_levels, int *symbol) +{ + int i = num_levels; + + *symbol = 1; + while (i--) + rc_get_bit(rc, p + *symbol, symbol); + *symbol -= 1 << num_levels; +} + +/* vi:set ts=4: */ |