archival/libunarchive/decompress_unlzma.c - codeaurora/busybox - Gitiles

 /*
  * Small lzma deflate implementation.
  * 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 <unistd.h>
 #include <stdio.h>
 #include <byteswap.h>

 #include "libbb.h"

 #include "unarchive.h"

 #include "rangecoder.h"


 typedef struct {
 	uint8_t pos;
 	uint32_t dict_size;
 	uint64_t dst_size;
 } __attribute__ ((packed)) lzma_header_t;


 #define LZMA_BASE_SIZE 1846
 #define LZMA_LIT_SIZE 768

 #define LZMA_NUM_POS_BITS_MAX 4

 #define LZMA_LEN_NUM_LOW_BITS 3
 #define LZMA_LEN_NUM_MID_BITS 3
 #define LZMA_LEN_NUM_HIGH_BITS 8

 #define LZMA_LEN_CHOICE 0
 #define LZMA_LEN_CHOICE_2 (LZMA_LEN_CHOICE + 1)
 #define LZMA_LEN_LOW (LZMA_LEN_CHOICE_2 + 1)
 #define LZMA_LEN_MID (LZMA_LEN_LOW \
 		      + (1 << (LZMA_NUM_POS_BITS_MAX + LZMA_LEN_NUM_LOW_BITS)))
 #define LZMA_LEN_HIGH (LZMA_LEN_MID \
 		       +(1 << (LZMA_NUM_POS_BITS_MAX + LZMA_LEN_NUM_MID_BITS)))
 #define LZMA_NUM_LEN_PROBS (LZMA_LEN_HIGH + (1 << LZMA_LEN_NUM_HIGH_BITS))

 #define LZMA_NUM_STATES 12
 #define LZMA_NUM_LIT_STATES 7

 #define LZMA_START_POS_MODEL_INDEX 4
 #define LZMA_END_POS_MODEL_INDEX 14
 #define LZMA_NUM_FULL_DISTANCES (1 << (LZMA_END_POS_MODEL_INDEX >> 1))

 #define LZMA_NUM_POS_SLOT_BITS 6
 #define LZMA_NUM_LEN_TO_POS_STATES 4

 #define LZMA_NUM_ALIGN_BITS 4

 #define LZMA_MATCH_MIN_LEN 2

 #define LZMA_IS_MATCH 0
 #define LZMA_IS_REP (LZMA_IS_MATCH + (LZMA_NUM_STATES <<LZMA_NUM_POS_BITS_MAX))
 #define LZMA_IS_REP_G0 (LZMA_IS_REP + LZMA_NUM_STATES)
 #define LZMA_IS_REP_G1 (LZMA_IS_REP_G0 + LZMA_NUM_STATES)
 #define LZMA_IS_REP_G2 (LZMA_IS_REP_G1 + LZMA_NUM_STATES)
 #define LZMA_IS_REP_0_LONG (LZMA_IS_REP_G2 + LZMA_NUM_STATES)
 #define LZMA_POS_SLOT (LZMA_IS_REP_0_LONG \
 		       + (LZMA_NUM_STATES << LZMA_NUM_POS_BITS_MAX))
 #define LZMA_SPEC_POS (LZMA_POS_SLOT \
 		       +(LZMA_NUM_LEN_TO_POS_STATES << LZMA_NUM_POS_SLOT_BITS))
 #define LZMA_ALIGN (LZMA_SPEC_POS \
 		    + LZMA_NUM_FULL_DISTANCES - LZMA_END_POS_MODEL_INDEX)
 #define LZMA_LEN_CODER (LZMA_ALIGN + (1 << LZMA_NUM_ALIGN_BITS))
 #define LZMA_REP_LEN_CODER (LZMA_LEN_CODER + LZMA_NUM_LEN_PROBS)
 #define LZMA_LITERAL (LZMA_REP_LEN_CODER + LZMA_NUM_LEN_PROBS)


 int unlzma(int src_fd, int dst_fd)
 {
 	lzma_header_t header;
 	int lc, pb, lp;
 	uint32_t pos_state_mask;
 	uint32_t literal_pos_mask;
 	uint32_t pos;
 	uint16_t *p;
 	uint16_t *prob;
 	uint16_t *prob_lit;
 	int num_bits;
 	int num_probs;
 	rc_t rc;
 	int i, mi;
 	uint8_t *buffer;
 	uint8_t previous_byte = 0;
 	size_t buffer_pos = 0, global_pos = 0;
 	int len = 0;
 	int state = 0;
 	uint32_t rep0 = 1, rep1 = 1, rep2 = 1, rep3 = 1;

 	if (read(src_fd, &header, sizeof(header)) != sizeof(header))
 		bb_error_msg_and_die("can't read header");

 	if (header.pos >= (9 * 5 * 5))
 		bb_error_msg_and_die("bad header");
 	mi = header.pos / 9;
 	lc = header.pos % 9;
 	pb = mi / 5;
 	lp = mi % 5;
 	pos_state_mask = (1 << pb) - 1;
 	literal_pos_mask = (1 << lp) - 1;

 	header.dict_size = SWAP_LE32(header.dict_size);
 	header.dst_size = SWAP_LE64(header.dst_size);

 	if (header.dict_size == 0)
 		header.dict_size = 1;

 	buffer = xmalloc(MIN(header.dst_size, header.dict_size));

 	num_probs = LZMA_BASE_SIZE + (LZMA_LIT_SIZE << (lc + lp));
 	p = xmalloc(num_probs * sizeof(*p));
 	num_probs = LZMA_LITERAL + (LZMA_LIT_SIZE << (lc + lp));
 	for (i = 0; i < num_probs; i++)
 		p[i] = (1 << RC_MODEL_TOTAL_BITS) >> 1;

 	rc_init(&rc, src_fd, 0x10000);

 	while (global_pos + buffer_pos < header.dst_size) {
 		int pos_state = (buffer_pos + global_pos) & pos_state_mask;

 		prob =
 			p + LZMA_IS_MATCH + (state << LZMA_NUM_POS_BITS_MAX) + pos_state;
 		if (rc_is_bit_0(&rc, prob)) {
 			mi = 1;
 			rc_update_bit_0(&rc, prob);
 			prob = (p + LZMA_LITERAL + (LZMA_LIT_SIZE
 					* ((((buffer_pos + global_pos) & literal_pos_mask) << lc)
 					+ (previous_byte >> (8 - lc)))));

 			if (state >= LZMA_NUM_LIT_STATES) {
 				int match_byte;

 				pos = buffer_pos - rep0;
 				while (pos >= header.dict_size)
 					pos += header.dict_size;
 				match_byte = buffer[pos];
 				do {
 					int bit;

 					match_byte <<= 1;
 					bit = match_byte & 0x100;
 					prob_lit = prob + 0x100 + bit + mi;
 					if (rc_get_bit(&rc, prob_lit, &mi)) {
 						if (!bit)
 							break;
 					} else {
 						if (bit)
 							break;
 					}
 				} while (mi < 0x100);
 			}
 			while (mi < 0x100) {
 				prob_lit = prob + mi;
 				rc_get_bit(&rc, prob_lit, &mi);
 			}
 			previous_byte = (uint8_t) mi;

 			buffer[buffer_pos++] = previous_byte;
 			if (buffer_pos == header.dict_size) {
 				buffer_pos = 0;
 				global_pos += header.dict_size;
 				write(dst_fd, buffer, header.dict_size);
 			}
 			if (state < 4)
 				state = 0;
 			else if (state < 10)
 				state -= 3;
 			else
 				state -= 6;
 		} else {
 			int offset;
 			uint16_t *prob_len;

 			rc_update_bit_1(&rc, prob);
 			prob = p + LZMA_IS_REP + state;
 			if (rc_is_bit_0(&rc, prob)) {
 				rc_update_bit_0(&rc, prob);
 				rep3 = rep2;
 				rep2 = rep1;
 				rep1 = rep0;
 				state = state < LZMA_NUM_LIT_STATES ? 0 : 3;
 				prob = p + LZMA_LEN_CODER;
 			} else {
 				rc_update_bit_1(&rc, prob);
 				prob = p + LZMA_IS_REP_G0 + state;
 				if (rc_is_bit_0(&rc, prob)) {
 					rc_update_bit_0(&rc, prob);
 					prob = (p + LZMA_IS_REP_0_LONG
 							+ (state << LZMA_NUM_POS_BITS_MAX) + pos_state);
 					if (rc_is_bit_0(&rc, prob)) {
 						rc_update_bit_0(&rc, prob);

 						state = state < LZMA_NUM_LIT_STATES ? 9 : 11;
 						pos = buffer_pos - rep0;
 						while (pos >= header.dict_size)
 							pos += header.dict_size;
 						previous_byte = buffer[pos];
 						buffer[buffer_pos++] = previous_byte;
 						if (buffer_pos == header.dict_size) {
 							buffer_pos = 0;
 							global_pos += header.dict_size;
 							write(dst_fd, buffer, header.dict_size);
 						}
 						continue;
 					} else {
 						rc_update_bit_1(&rc, prob);
 					}
 				} else {
 					uint32_t distance;

 					rc_update_bit_1(&rc, prob);
 					prob = p + LZMA_IS_REP_G1 + state;
 					if (rc_is_bit_0(&rc, prob)) {
 						rc_update_bit_0(&rc, prob);
 						distance = rep1;
 					} else {
 						rc_update_bit_1(&rc, prob);
 						prob = p + LZMA_IS_REP_G2 + state;
 						if (rc_is_bit_0(&rc, prob)) {
 							rc_update_bit_0(&rc, prob);
 							distance = rep2;
 						} else {
 							rc_update_bit_1(&rc, prob);
 							distance = rep3;
 							rep3 = rep2;
 						}
 						rep2 = rep1;
 					}
 					rep1 = rep0;
 					rep0 = distance;
 				}
 				state = state < LZMA_NUM_LIT_STATES ? 8 : 11;
 				prob = p + LZMA_REP_LEN_CODER;
 			}

 			prob_len = prob + LZMA_LEN_CHOICE;
 			if (rc_is_bit_0(&rc, prob_len)) {
 				rc_update_bit_0(&rc, prob_len);
 				prob_len = (prob + LZMA_LEN_LOW
 							+ (pos_state << LZMA_LEN_NUM_LOW_BITS));
 				offset = 0;
 				num_bits = LZMA_LEN_NUM_LOW_BITS;
 			} else {
 				rc_update_bit_1(&rc, prob_len);
 				prob_len = prob + LZMA_LEN_CHOICE_2;
 				if (rc_is_bit_0(&rc, prob_len)) {
 					rc_update_bit_0(&rc, prob_len);
 					prob_len = (prob + LZMA_LEN_MID
 								+ (pos_state << LZMA_LEN_NUM_MID_BITS));
 					offset = 1 << LZMA_LEN_NUM_LOW_BITS;
 					num_bits = LZMA_LEN_NUM_MID_BITS;
 				} else {
 					rc_update_bit_1(&rc, prob_len);
 					prob_len = prob + LZMA_LEN_HIGH;
 					offset = ((1 << LZMA_LEN_NUM_LOW_BITS)
 							  + (1 << LZMA_LEN_NUM_MID_BITS));
 					num_bits = LZMA_LEN_NUM_HIGH_BITS;
 				}
 			}
 			rc_bit_tree_decode(&rc, prob_len, num_bits, &len);
 			len += offset;

 			if (state < 4) {
 				int pos_slot;

 				state += LZMA_NUM_LIT_STATES;
 				prob =
 					p + LZMA_POS_SLOT +
 					((len <
 					  LZMA_NUM_LEN_TO_POS_STATES ? len :
 					  LZMA_NUM_LEN_TO_POS_STATES - 1)
 					 << LZMA_NUM_POS_SLOT_BITS);
 				rc_bit_tree_decode(&rc, prob, LZMA_NUM_POS_SLOT_BITS,
 								   &pos_slot);
 				if (pos_slot >= LZMA_START_POS_MODEL_INDEX) {
 					num_bits = (pos_slot >> 1) - 1;
 					rep0 = 2 | (pos_slot & 1);
 					if (pos_slot < LZMA_END_POS_MODEL_INDEX) {
 						rep0 <<= num_bits;
 						prob = p + LZMA_SPEC_POS + rep0 - pos_slot - 1;
 					} else {
 						num_bits -= LZMA_NUM_ALIGN_BITS;
 						while (num_bits--)
 							rep0 = (rep0 << 1) | rc_direct_bit(&rc);
 						prob = p + LZMA_ALIGN;
 						rep0 <<= LZMA_NUM_ALIGN_BITS;
 						num_bits = LZMA_NUM_ALIGN_BITS;
 					}
 					i = 1;
 					mi = 1;
 					while (num_bits--) {
 						if (rc_get_bit(&rc, prob + mi, &mi))
 							rep0 |= i;
 						i <<= 1;
 					}
 				} else
 					rep0 = pos_slot;
 				if (++rep0 == 0)
 					break;
 			}

 			len += LZMA_MATCH_MIN_LEN;

 			do {
 				pos = buffer_pos - rep0;
 				while (pos >= header.dict_size)
 					pos += header.dict_size;
 				previous_byte = buffer[pos];
 				buffer[buffer_pos++] = previous_byte;
 				if (buffer_pos == header.dict_size) {
 					buffer_pos = 0;
 					global_pos += header.dict_size;
 					write(dst_fd, buffer, header.dict_size);
 				}
 				len--;
 			} while (len != 0 && buffer_pos < header.dst_size);
 		}
 	}

 	write(dst_fd, buffer, buffer_pos);
 	rc_free(&rc);
 	return 0;
 }

 /* vi:set ts=4: */
	/*
	* Small lzma deflate implementation.
	* 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 <unistd.h>
	#include <stdio.h>
	#include <byteswap.h>

	#include "libbb.h"

	#include "unarchive.h"

	#include "rangecoder.h"


	typedef struct {
	uint8_t pos;
	uint32_t dict_size;
	uint64_t dst_size;
	} __attribute__ ((packed)) lzma_header_t;


	#define LZMA_BASE_SIZE 1846
	#define LZMA_LIT_SIZE 768

	#define LZMA_NUM_POS_BITS_MAX 4

	#define LZMA_LEN_NUM_LOW_BITS 3
	#define LZMA_LEN_NUM_MID_BITS 3
	#define LZMA_LEN_NUM_HIGH_BITS 8

	#define LZMA_LEN_CHOICE 0
	#define LZMA_LEN_CHOICE_2 (LZMA_LEN_CHOICE + 1)
	#define LZMA_LEN_LOW (LZMA_LEN_CHOICE_2 + 1)
	#define LZMA_LEN_MID (LZMA_LEN_LOW \
	+ (1 << (LZMA_NUM_POS_BITS_MAX + LZMA_LEN_NUM_LOW_BITS)))
	#define LZMA_LEN_HIGH (LZMA_LEN_MID \
	+(1 << (LZMA_NUM_POS_BITS_MAX + LZMA_LEN_NUM_MID_BITS)))
	#define LZMA_NUM_LEN_PROBS (LZMA_LEN_HIGH + (1 << LZMA_LEN_NUM_HIGH_BITS))

	#define LZMA_NUM_STATES 12
	#define LZMA_NUM_LIT_STATES 7

	#define LZMA_START_POS_MODEL_INDEX 4
	#define LZMA_END_POS_MODEL_INDEX 14
	#define LZMA_NUM_FULL_DISTANCES (1 << (LZMA_END_POS_MODEL_INDEX >> 1))

	#define LZMA_NUM_POS_SLOT_BITS 6
	#define LZMA_NUM_LEN_TO_POS_STATES 4

	#define LZMA_NUM_ALIGN_BITS 4

	#define LZMA_MATCH_MIN_LEN 2

	#define LZMA_IS_MATCH 0
	#define LZMA_IS_REP (LZMA_IS_MATCH + (LZMA_NUM_STATES <<LZMA_NUM_POS_BITS_MAX))
	#define LZMA_IS_REP_G0 (LZMA_IS_REP + LZMA_NUM_STATES)
	#define LZMA_IS_REP_G1 (LZMA_IS_REP_G0 + LZMA_NUM_STATES)
	#define LZMA_IS_REP_G2 (LZMA_IS_REP_G1 + LZMA_NUM_STATES)
	#define LZMA_IS_REP_0_LONG (LZMA_IS_REP_G2 + LZMA_NUM_STATES)
	#define LZMA_POS_SLOT (LZMA_IS_REP_0_LONG \
	+ (LZMA_NUM_STATES << LZMA_NUM_POS_BITS_MAX))
	#define LZMA_SPEC_POS (LZMA_POS_SLOT \
	+(LZMA_NUM_LEN_TO_POS_STATES << LZMA_NUM_POS_SLOT_BITS))
	#define LZMA_ALIGN (LZMA_SPEC_POS \
	+ LZMA_NUM_FULL_DISTANCES - LZMA_END_POS_MODEL_INDEX)
	#define LZMA_LEN_CODER (LZMA_ALIGN + (1 << LZMA_NUM_ALIGN_BITS))
	#define LZMA_REP_LEN_CODER (LZMA_LEN_CODER + LZMA_NUM_LEN_PROBS)
	#define LZMA_LITERAL (LZMA_REP_LEN_CODER + LZMA_NUM_LEN_PROBS)


	int unlzma(int src_fd, int dst_fd)
	{
	lzma_header_t header;
	int lc, pb, lp;
	uint32_t pos_state_mask;
	uint32_t literal_pos_mask;
	uint32_t pos;
	uint16_t *p;
	uint16_t *prob;
	uint16_t *prob_lit;
	int num_bits;
	int num_probs;
	rc_t rc;
	int i, mi;
	uint8_t *buffer;
	uint8_t previous_byte = 0;
	size_t buffer_pos = 0, global_pos = 0;
	int len = 0;
	int state = 0;
	uint32_t rep0 = 1, rep1 = 1, rep2 = 1, rep3 = 1;

	if (read(src_fd, &header, sizeof(header)) != sizeof(header))
	bb_error_msg_and_die("can't read header");

	if (header.pos >= (9 * 5 * 5))
	bb_error_msg_and_die("bad header");
	mi = header.pos / 9;
	lc = header.pos % 9;
	pb = mi / 5;
	lp = mi % 5;
	pos_state_mask = (1 << pb) - 1;
	literal_pos_mask = (1 << lp) - 1;

	header.dict_size = SWAP_LE32(header.dict_size);
	header.dst_size = SWAP_LE64(header.dst_size);

	if (header.dict_size == 0)
	header.dict_size = 1;

	buffer = xmalloc(MIN(header.dst_size, header.dict_size));

	num_probs = LZMA_BASE_SIZE + (LZMA_LIT_SIZE << (lc + lp));
	p = xmalloc(num_probs * sizeof(*p));
	num_probs = LZMA_LITERAL + (LZMA_LIT_SIZE << (lc + lp));
	for (i = 0; i < num_probs; i++)
	p[i] = (1 << RC_MODEL_TOTAL_BITS) >> 1;

	rc_init(&rc, src_fd, 0x10000);

	while (global_pos + buffer_pos < header.dst_size) {
	int pos_state = (buffer_pos + global_pos) & pos_state_mask;

	prob =
	p + LZMA_IS_MATCH + (state << LZMA_NUM_POS_BITS_MAX) + pos_state;
	if (rc_is_bit_0(&rc, prob)) {
	mi = 1;
	rc_update_bit_0(&rc, prob);
	prob = (p + LZMA_LITERAL + (LZMA_LIT_SIZE
	* ((((buffer_pos + global_pos) & literal_pos_mask) << lc)
	+ (previous_byte >> (8 - lc)))));

	if (state >= LZMA_NUM_LIT_STATES) {
	int match_byte;

	pos = buffer_pos - rep0;
	while (pos >= header.dict_size)
	pos += header.dict_size;
	match_byte = buffer[pos];
	do {
	int bit;

	match_byte <<= 1;
	bit = match_byte & 0x100;
	prob_lit = prob + 0x100 + bit + mi;
	if (rc_get_bit(&rc, prob_lit, &mi)) {
	if (!bit)
	break;
	} else {
	if (bit)
	break;
	}
	} while (mi < 0x100);
	}
	while (mi < 0x100) {
	prob_lit = prob + mi;
	rc_get_bit(&rc, prob_lit, &mi);
	}
	previous_byte = (uint8_t) mi;

	buffer[buffer_pos++] = previous_byte;
	if (buffer_pos == header.dict_size) {
	buffer_pos = 0;
	global_pos += header.dict_size;
	write(dst_fd, buffer, header.dict_size);
	}
	if (state < 4)
	state = 0;
	else if (state < 10)
	state -= 3;
	else
	state -= 6;
	} else {
	int offset;
	uint16_t *prob_len;

	rc_update_bit_1(&rc, prob);
	prob = p + LZMA_IS_REP + state;
	if (rc_is_bit_0(&rc, prob)) {
	rc_update_bit_0(&rc, prob);
	rep3 = rep2;
	rep2 = rep1;
	rep1 = rep0;
	state = state < LZMA_NUM_LIT_STATES ? 0 : 3;
	prob = p + LZMA_LEN_CODER;
	} else {
	rc_update_bit_1(&rc, prob);
	prob = p + LZMA_IS_REP_G0 + state;
	if (rc_is_bit_0(&rc, prob)) {
	rc_update_bit_0(&rc, prob);
	prob = (p + LZMA_IS_REP_0_LONG
	+ (state << LZMA_NUM_POS_BITS_MAX) + pos_state);
	if (rc_is_bit_0(&rc, prob)) {
	rc_update_bit_0(&rc, prob);

	state = state < LZMA_NUM_LIT_STATES ? 9 : 11;
	pos = buffer_pos - rep0;
	while (pos >= header.dict_size)
	pos += header.dict_size;
	previous_byte = buffer[pos];
	buffer[buffer_pos++] = previous_byte;
	if (buffer_pos == header.dict_size) {
	buffer_pos = 0;
	global_pos += header.dict_size;
	write(dst_fd, buffer, header.dict_size);
	}
	continue;
	} else {
	rc_update_bit_1(&rc, prob);
	}
	} else {
	uint32_t distance;

	rc_update_bit_1(&rc, prob);
	prob = p + LZMA_IS_REP_G1 + state;
	if (rc_is_bit_0(&rc, prob)) {
	rc_update_bit_0(&rc, prob);
	distance = rep1;
	} else {
	rc_update_bit_1(&rc, prob);
	prob = p + LZMA_IS_REP_G2 + state;
	if (rc_is_bit_0(&rc, prob)) {
	rc_update_bit_0(&rc, prob);
	distance = rep2;
	} else {
	rc_update_bit_1(&rc, prob);
	distance = rep3;
	rep3 = rep2;
	}
	rep2 = rep1;
	}
	rep1 = rep0;
	rep0 = distance;
	}
	state = state < LZMA_NUM_LIT_STATES ? 8 : 11;
	prob = p + LZMA_REP_LEN_CODER;
	}

	prob_len = prob + LZMA_LEN_CHOICE;
	if (rc_is_bit_0(&rc, prob_len)) {
	rc_update_bit_0(&rc, prob_len);
	prob_len = (prob + LZMA_LEN_LOW
	+ (pos_state << LZMA_LEN_NUM_LOW_BITS));
	offset = 0;
	num_bits = LZMA_LEN_NUM_LOW_BITS;
	} else {
	rc_update_bit_1(&rc, prob_len);
	prob_len = prob + LZMA_LEN_CHOICE_2;
	if (rc_is_bit_0(&rc, prob_len)) {
	rc_update_bit_0(&rc, prob_len);
	prob_len = (prob + LZMA_LEN_MID
	+ (pos_state << LZMA_LEN_NUM_MID_BITS));
	offset = 1 << LZMA_LEN_NUM_LOW_BITS;
	num_bits = LZMA_LEN_NUM_MID_BITS;
	} else {
	rc_update_bit_1(&rc, prob_len);
	prob_len = prob + LZMA_LEN_HIGH;
	offset = ((1 << LZMA_LEN_NUM_LOW_BITS)
	+ (1 << LZMA_LEN_NUM_MID_BITS));
	num_bits = LZMA_LEN_NUM_HIGH_BITS;
	}
	}
	rc_bit_tree_decode(&rc, prob_len, num_bits, &len);
	len += offset;

	if (state < 4) {
	int pos_slot;

	state += LZMA_NUM_LIT_STATES;
	prob =
	p + LZMA_POS_SLOT +
	((len <
	LZMA_NUM_LEN_TO_POS_STATES ? len :
	LZMA_NUM_LEN_TO_POS_STATES - 1)
	<< LZMA_NUM_POS_SLOT_BITS);
	rc_bit_tree_decode(&rc, prob, LZMA_NUM_POS_SLOT_BITS,
	&pos_slot);
	if (pos_slot >= LZMA_START_POS_MODEL_INDEX) {
	num_bits = (pos_slot >> 1) - 1;
	rep0 = 2 \| (pos_slot & 1);
	if (pos_slot < LZMA_END_POS_MODEL_INDEX) {
	rep0 <<= num_bits;
	prob = p + LZMA_SPEC_POS + rep0 - pos_slot - 1;
	} else {
	num_bits -= LZMA_NUM_ALIGN_BITS;
	while (num_bits--)
	rep0 = (rep0 << 1) \| rc_direct_bit(&rc);
	prob = p + LZMA_ALIGN;
	rep0 <<= LZMA_NUM_ALIGN_BITS;
	num_bits = LZMA_NUM_ALIGN_BITS;
	}
	i = 1;
	mi = 1;
	while (num_bits--) {
	if (rc_get_bit(&rc, prob + mi, &mi))
	rep0 \|= i;
	i <<= 1;
	}
	} else
	rep0 = pos_slot;
	if (++rep0 == 0)
	break;
	}

	len += LZMA_MATCH_MIN_LEN;

	do {
	pos = buffer_pos - rep0;
	while (pos >= header.dict_size)
	pos += header.dict_size;
	previous_byte = buffer[pos];
	buffer[buffer_pos++] = previous_byte;
	if (buffer_pos == header.dict_size) {
	buffer_pos = 0;
	global_pos += header.dict_size;
	write(dst_fd, buffer, header.dict_size);
	}
	len--;
	} while (len != 0 && buffer_pos < header.dst_size);
	}
	}

	write(dst_fd, buffer, buffer_pos);
	rc_free(&rc);
	return 0;
	}

	/* vi:set ts=4: */