text: /*
   * LZMA2 decoder
   *
   * Authors: Lasse Collin <lasse.collin@tukaani.org>
   *          Igor Pavlov <http://7-zip.org/>
   *
   * This file has been put into the public domain.
   * You can do whatever you want with this file.
   */
  
  #include "private.h"
  #include "lzma2.h"
  
  /*
   * Range decoder initialization eats the first five bytes of each LZMA chunk.
   */
  #define RC_INIT_BYTES 5
  
  /*
   * Minimum number of usable input buffer to safely decode one LZMA symbol.
   * The worst case is that we decode 22 bits using probabilities and 26
   * direct bits. This may decode at maximum of 20 bytes of input. However,
   * lzma_main() does an extra normalization before returning, thus we
   * need to put 21 here.
   */
  #define LZMA_IN_REQUIRED 21
  
  /*
   * Dictionary (history buffer)
   *
   * These are always true:
   *    start <= pos <= full <= end
   *    pos <= limit <= end
   *
   * In multi-call mode, also these are true:
   *    end == size
   *    size <= size_max
   *    allocated <= size
   *
   * Most of these variables are size_t to support single-call mode,
   * in which the dictionary variables address the actual output
   * buffer directly.
   */
  struct dictionary {
  	/* Beginning of the history buffer */
  	uint8_t *buf;
  
  	/* Old position in buf (before decoding more data) */
  	size_t start;
  
  	/* Position in buf */
  	size_t pos;
  
  	/*
  	 * How full dictionary is. This is used to detect corrupt input that
  	 * would read beyond the beginning of the uncompressed stream.
  	 */
  	size_t full;
  
  	/* Write limit; we don't write to buf[limit] or later bytes. */
  	size_t limit;
  
  	/*
  	 * End of the dictionary buffer. In multi-call mode, this is
  	 * the same as the dictionary size. In single-call mode, this
  	 * indicates the size of the output buffer.
  	 */
  	size_t end;
  
  	/*
  	 * Size of the dictionary as specified in Block Header. This is used
  	 * together with "full" to detect corrupt input that would make us
  	 * read beyond the beginning of the uncompressed stream.
  	 */
  	uint32_t size;
  
  	/*
  	 * Maximum allowed dictionary size in multi-call mode.
  	 * This is ignored in single-call mode.
  	 */
  	uint32_t size_max;
  
  	/*
  	 * Amount of memory currently allocated for the dictionary.
  	 * This is used only with XZ_DYNALLOC. (With XZ_PREALLOC,
  	 * size_max is always the same as the allocated size.)
  	 */
  	uint32_t allocated;
  
  	/* Operation mode */
  	enum xz_mode mode;
  };
  
  /* Range decoder */
  struct rc_dec {
  	uint32_t range;
  	uint32_t code;
  
  	/*
  	 * Number of initializing bytes remaining to be read
  	 * by rc_read_init().
  	 */
  	uint32_t init_bytes_left;
  
  	/*
  	 * Buffer from which we read our input. It can be either
  	 * temp.buf or the caller-provided input buffer.
  	 */
  	const uint8_t *in;
  	size_t in_pos;
  	size_t in_limit;
  };
  
  /* Probabilities for a length decoder. */
  struct lzma_len_dec {
  	/* Probability of match length being at least 10 */
  	uint16_t choice;
  
  	/* Probability of match length being at least 18 */
  	uint16_t choice2;
  
  	/* Probabilities for match lengths 2-9 */
  	uint16_t low[POS_STATES_MAX][LEN_LOW_SYMBOLS];
  
  	/* Probabilities for match lengths 10-17 */
  	uint16_t mid[POS_STATES_MAX][LEN_MID_SYMBOLS];
  
  	/* Probabilities for match lengths 18-273 */
  	uint16_t high[LEN_HIGH_SYMBOLS];
  };
  
  struct lzma_dec {
  	/* Distances of latest four matches */
  	uint32_t rep0;
  	uint32_t rep1;
  	uint32_t rep2;
  	uint32_t rep3;
  
  	/* Types of the most recently seen LZMA symbols */
  	enum lzma_state state;
  
  	/*
  	 * Length of a match. This is updated so that dict_repeat can
  	 * be called again to finish repeating the whole match.
  	 */
  	uint32_t len;
  
  	/*
  	 * LZMA properties or related bit masks (number of literal
  	 * context bits, a mask dervied from the number of literal
  	 * position bits, and a mask dervied from the number
  	 * position bits)
  	 */
  	uint32_t lc;
  	uint32_t literal_pos_mask; /* (1 << lp) - 1 */
  	uint32_t pos_mask;         /* (1 << pb) - 1 */
  
  	/* If 1, it's a match. Otherwise it's a single 8-bit literal. */
  	uint16_t is_match[STATES][POS_STATES_MAX];
  
  	/* If 1, it's a repeated match. The distance is one of rep0 .. rep3. */
  	uint16_t is_rep[STATES];
  
  	/*
  	 * If 0, distance of a repeated match is rep0.
  	 * Otherwise check is_rep1.
  	 */
  	uint16_t is_rep0[STATES];
  
  	/*
  	 * If 0, distance of a repeated match is rep1.
  	 * Otherwise check is_rep2.
  	 */
  	uint16_t is_rep1[STATES];
  
  	/* If 0, distance of a repeated match is rep2. Otherwise it is rep3. */
  	uint16_t is_rep2[STATES];
  
  	/*
  	 * If 1, the repeated match has length of one byte. Otherwise
  	 * the length is decoded from rep_len_decoder.
  	 */
  	uint16_t is_rep0_long[STATES][POS_STATES_MAX];
  
  	/*
  	 * Probability tree for the highest two bits of the match
  	 * distance. There is a separate probability tree for match
  	 * lengths of 2 (i.e. MATCH_LEN_MIN), 3, 4, and [5, 273].
  	 */
  	uint16_t dist_slot[DIST_STATES][DIST_SLOTS];
  
  	/*
  	 * Probility trees for additional bits for match distance
  	 * when the distance is in the range [4, 127].
  	 */
  	uint16_t dist_special[FULL_DISTANCES - DIST_MODEL_END];
  
  	/*
  	 * Probability tree for the lowest four bits of a match
  	 * distance that is equal to or greater than 128.
  	 */
  	uint16_t dist_align[ALIGN_SIZE];
  
  	/* Length of a normal match */
  	struct lzma_len_dec match_len_dec;
  
  	/* Length of a repeated match */
  	struct lzma_len_dec rep_len_dec;
  
  	/* Probabilities of literals */
  	uint16_t literal[LITERAL_CODERS_MAX][LITERAL_CODER_SIZE];
  };
  
  struct lzma2_dec {
  	/* Position in xz_dec_lzma2_run(). */
  	enum lzma2_seq {
  		SEQ_CONTROL,
  		SEQ_UNCOMPRESSED_1,
  		SEQ_UNCOMPRESSED_2,
  		SEQ_COMPRESSED_0,
  		SEQ_COMPRESSED_1,
  		SEQ_PROPERTIES,
  		SEQ_LZMA_PREPARE,
  		SEQ_LZMA_RUN,
  		SEQ_COPY
  	} sequence;
  
  	/* Next position after decoding the compressed size of the chunk. */
  	enum lzma2_seq next_sequence;
  
  	/* Uncompressed size of LZMA chunk (2 MiB at maximum) */
  	uint32_t uncompressed;
  
  	/*
  	 * Compressed size of LZMA chunk or compressed/uncompressed
  	 * size of uncompressed chunk (64 KiB at maximum)
  	 */
  	uint32_t compressed;
  
  	/*
  	 * True if dictionary reset is needed. This is false before
  	 * the first chunk (LZMA or uncompressed).
  	 */
  	bool_t need_dict_reset;
  
  	/*
  	 * True if new LZMA properties are needed. This is false
  	 * before the first LZMA chunk.
  	 */
  	bool_t need_props;
  };
  
  struct xz_dec_lzma2 {
  	/*
  	 * The order below is important on x86 to reduce code size and
  	 * it shouldn't hurt on other platforms. Everything up to and
  	 * including lzma.pos_mask are in the first 128 bytes on x86-32,
  	 * which allows using smaller instructions to access those
  	 * variables. On x86-64, fewer variables fit into the first 128
  	 * bytes, but this is still the best order without sacrificing
  	 * the readability by splitting the structures.
  	 */
  	struct rc_dec rc;
  	struct dictionary dict;
  	struct lzma2_dec lzma2;
  	struct lzma_dec lzma;
  
  	/*
  	 * Temporary buffer which holds small number of input bytes between
  	 * decoder calls. See lzma2_lzma() for details.
  	 */
  	struct {
  		uint32_t size;
  		uint8_t buf[3 * LZMA_IN_REQUIRED];
  	} temp;
  };
  
  /**************
   * Dictionary *
   **************/
  
  /*
   * Reset the dictionary state. When in single-call mode, set up the beginning
   * of the dictionary to point to the actual output buffer.
   */
  static void INIT dict_reset(struct dictionary *dict, struct xz_buf *b)
  {
  	if (DEC_IS_SINGLE(dict->mode)) {
  		dict->buf = b->out + b->out_pos;
  		dict->end = b->out_size - b->out_pos;
  	}
  
  	dict->start = 0;
  	dict->pos = 0;
  	dict->limit = 0;
  	dict->full = 0;
  }
  
  /* Set dictionary write limit */
  static void INIT dict_limit(struct dictionary *dict, size_t out_max)
  {
  	if (dict->end - dict->pos <= out_max)
  		dict->limit = dict->end;
  	else
  		dict->limit = dict->pos + out_max;
  }
  
  /* Return true if at least one byte can be written into the dictionary. */
  static inline bool_t INIT dict_has_space(const struct dictionary *dict)
  {
  	return dict->pos < dict->limit;
  }
  
  /*
   * Get a byte from the dictionary at the given distance. The distance is
   * assumed to valid, or as a special case, zero when the dictionary is
   * still empty. This special case is needed for single-call decoding to
   * avoid writing a '\0' to the end of the destination buffer.
   */
  static inline uint32_t INIT dict_get(const struct dictionary *dict, uint32_t dist)
  {
  	size_t offset = dict->pos - dist - 1;
  
  	if (dist >= dict->pos)
  		offset += dict->end;
  
  	return dict->full > 0 ? dict->buf[offset] : 0;
  }
  
  /*
   * Put one byte into the dictionary. It is assumed that there is space for it.
   */
  static inline void INIT dict_put(struct dictionary *dict, uint8_t byte)
  {
  	dict->buf[dict->pos++] = byte;
  
  	if (dict->full < dict->pos)
  		dict->full = dict->pos;
  }
  
  /*
   * Repeat given number of bytes from the given distance. If the distance is
   * invalid, false is returned. On success, true is returned and *len is
   * updated to indicate how many bytes were left to be repeated.
   */
  static bool_t INIT dict_repeat(struct dictionary *dict, uint32_t *len, uint32_t dist)
  {
  	size_t back;
  	uint32_t left;
  
  	if (dist >= dict->full || dist >= dict->size)
  		return false;
  
  	left = min_t(size_t, dict->limit - dict->pos, *len);
  	*len -= left;
  
  	back = dict->pos - dist - 1;
  	if (dist >= dict->pos)
  		back += dict->end;
  
  	do {
  		dict->buf[dict->pos++] = dict->buf[back++];
  		if (back == dict->end)
  			back = 0;
  	} while (--left > 0);
  
  	if (dict->full < dict->pos)
  		dict->full = dict->pos;
  
  	return true;
  }
  
  /* Copy uncompressed data as is from input to dictionary and output buffers. */
  static void INIT dict_uncompressed(struct dictionary *dict, struct xz_buf *b,
  				   uint32_t *left)
  {
  	size_t copy_size;
  
  	while (*left > 0 && b->in_pos < b->in_size
  			&& b->out_pos < b->out_size) {
  		copy_size = min(b->in_size - b->in_pos,
  				b->out_size - b->out_pos);
  		if (copy_size > dict->end - dict->pos)
  			copy_size = dict->end - dict->pos;
  		if (copy_size > *left)
  			copy_size = *left;
  
  		*left -= copy_size;
  
  		memcpy(dict->buf + dict->pos, b->in + b->in_pos, copy_size);
  		dict->pos += copy_size;
  
  		if (dict->full < dict->pos)
  			dict->full = dict->pos;
  
  		if (DEC_IS_MULTI(dict->mode)) {
  			if (dict->pos == dict->end)
  				dict->pos = 0;
  
  			memcpy(b->out + b->out_pos, b->in + b->in_pos,
  					copy_size);
  		}
  
  		dict->start = dict->pos;
  
  		b->out_pos += copy_size;
  		b->in_pos += copy_size;
  	}
  }
  
  /*
   * Flush pending data from dictionary to b->out. It is assumed that there is
   * enough space in b->out. This is guaranteed because caller uses dict_limit()
   * before decoding data into the dictionary.
   */
  static uint32_t INIT dict_flush(struct dictionary *dict, struct xz_buf *b)
  {
  	size_t copy_size = dict->pos - dict->start;
  
  	if (DEC_IS_MULTI(dict->mode)) {
  		if (dict->pos == dict->end)
  			dict->pos = 0;
  
  		memcpy(b->out + b->out_pos, dict->buf + dict->start,
  				copy_size);
  	}
  
  	dict->start = dict->pos;
  	b->out_pos += copy_size;
  	return copy_size;
  }
  
  /*****************
   * Range decoder *
   *****************/
  
  /* Reset the range decoder. */
  static void INIT rc_reset(struct rc_dec *rc)
  {
  	rc->range = (uint32_t)-1;
  	rc->code = 0;
  	rc->init_bytes_left = RC_INIT_BYTES;
  }
  
  /*
   * Read the first five initial bytes into rc->code if they haven't been
   * read already. (Yes, the first byte gets completely ignored.)
   */
  static bool_t INIT rc_read_init(struct rc_dec *rc, struct xz_buf *b)
  {
  	while (rc->init_bytes_left > 0) {
  		if (b->in_pos == b->in_size)
  			return false;
  
  		rc->code = (rc->code << 8) + b->in[b->in_pos++];
  		--rc->init_bytes_left;
  	}
  
  	return true;
  }
  
  /* Return true if there may not be enough input for the next decoding loop. */
  static inline bool_t INIT rc_limit_exceeded(const struct rc_dec *rc)
  {
  	return rc->in_pos > rc->in_limit;
  }
  
  /*
   * Return true if it is possible (from point of view of range decoder) that
   * we have reached the end of the LZMA chunk.
   */
  static inline bool_t INIT rc_is_finished(const struct rc_dec *rc)
  {
  	return rc->code == 0;
  }
  
  /* Read the next input byte if needed. */
  static always_inline void rc_normalize(struct rc_dec *rc)
  {
  	if (rc->range < RC_TOP_VALUE) {
  		rc->range <<= RC_SHIFT_BITS;
  		rc->code = (rc->code << RC_SHIFT_BITS) + rc->in[rc->in_pos++];
  	}
  }
  
  /*
   * Decode one bit. In some versions, this function has been splitted in three
   * functions so that the compiler is supposed to be able to more easily avoid
   * an extra branch. In this particular version of the LZMA decoder, this
   * doesn't seem to be a good idea (tested with GCC 3.3.6, 3.4.6, and 4.3.3
   * on x86). Using a non-splitted version results in nicer looking code too.
   *
   * NOTE: This must return an int. Do not make it return a bool or the speed
   * of the code generated by GCC 3.x decreases 10-15 %. (GCC 4.3 doesn't care,
   * and it generates 10-20 % faster code than GCC 3.x from this file anyway.)
   */
  static always_inline int rc_bit(struct rc_dec *rc, uint16_t *prob)
  {
  	uint32_t bound;
  	int bit;
  
  	rc_normalize(rc);
  	bound = (rc->range >> RC_BIT_MODEL_TOTAL_BITS) * *prob;
  	if (rc->code < bound) {
  		rc->range = bound;
  		*prob += (RC_BIT_MODEL_TOTAL - *prob) >> RC_MOVE_BITS;
  		bit = 0;
  	} else {
  		rc->range -= bound;
  		rc->code -= bound;
  		*prob -= *prob >> RC_MOVE_BITS;
  		bit = 1;
  	}
  
  	return bit;
  }
  
  /* Decode a bittree starting from the most significant bit. */
  static always_inline uint32_t rc_bittree(struct rc_dec *rc,
  					 uint16_t *probs, uint32_t limit)
  {
  	uint32_t symbol = 1;
  
  	do {
  		if (rc_bit(rc, &probs[symbol]))
  			symbol = (symbol << 1) + 1;
  		else
  			symbol <<= 1;
  	} while (symbol < limit);
  
  	return symbol;
  }
  
  /* Decode a bittree starting from the least significant bit. */
  static always_inline void rc_bittree_reverse(struct rc_dec *rc,
  					     uint16_t *probs,
  					     uint32_t *dest, uint32_t limit)
  {
  	uint32_t symbol = 1;
  	uint32_t i = 0;
  
  	do {
  		if (rc_bit(rc, &probs[symbol])) {
  			symbol = (symbol << 1) + 1;
  			*dest += 1 << i;
  		} else {
  			symbol <<= 1;
  		}
  	} while (++i < limit);
  }
  
  /* Decode direct bits (fixed fifty-fifty probability) */
  static inline void INIT rc_direct(struct rc_dec *rc, uint32_t *dest, uint32_t limit)
  {
  	uint32_t mask;
  
  	do {
  		rc_normalize(rc);
  		rc->range >>= 1;
  		rc->code -= rc->range;
  		mask = (uint32_t)0 - (rc->code >> 31);
  		rc->code += rc->range & mask;
  		*dest = (*dest << 1) + (mask + 1);
  	} while (--limit > 0);
  }
  
  /********
   * LZMA *
   ********/
  
  /* Get pointer to literal coder probability array. */
  static uint16_t *INIT lzma_literal_probs(struct xz_dec_lzma2 *s)
  {
  	uint32_t prev_byte = dict_get(&s->dict, 0);
  	uint32_t low = prev_byte >> (8 - s->lzma.lc);
  	uint32_t high = (s->dict.pos & s->lzma.literal_pos_mask) << s->lzma.lc;
  	return s->lzma.literal[low + high];
  }
  
  /* Decode a literal (one 8-bit byte) */
  static void INIT lzma_literal(struct xz_dec_lzma2 *s)
  {
  	uint16_t *probs;
  	uint32_t symbol;
  	uint32_t match_byte;
  	uint32_t match_bit;
  	uint32_t offset;
  	uint32_t i;
  
  	probs = lzma_literal_probs(s);
  
  	if (lzma_state_is_literal(s->lzma.state)) {
  		symbol = rc_bittree(&s->rc, probs, 0x100);
  	} else {
  		symbol = 1;
  		match_byte = dict_get(&s->dict, s->lzma.rep0) << 1;
  		offset = 0x100;
  
  		do {
  			match_bit = match_byte & offset;
  			match_byte <<= 1;
  			i = offset + match_bit + symbol;
  
  			if (rc_bit(&s->rc, &probs[i])) {
  				symbol = (symbol << 1) + 1;
  				offset &= match_bit;
  			} else {
  				symbol <<= 1;
  				offset &= ~match_bit;
  			}
  		} while (symbol < 0x100);
  	}
  
  	dict_put(&s->dict, (uint8_t)symbol);
  	lzma_state_literal(&s->lzma.state);
  }
  
  /* Decode the length of the match into s->lzma.len. */
  static void INIT lzma_len(struct xz_dec_lzma2 *s, struct lzma_len_dec *l,
  			  uint32_t pos_state)
  {
  	uint16_t *probs;
  	uint32_t limit;
  
  	if (!rc_bit(&s->rc, &l->choice)) {
  		probs = l->low[pos_state];
  		limit = LEN_LOW_SYMBOLS;
  		s->lzma.len = MATCH_LEN_MIN;
  	} else {
  		if (!rc_bit(&s->rc, &l->choice2)) {
  			probs = l->mid[pos_state];
  			limit = LEN_MID_SYMBOLS;
  			s->lzma.len = MATCH_LEN_MIN + LEN_LOW_SYMBOLS;
  		} else {
  			probs = l->high;
  			limit = LEN_HIGH_SYMBOLS;
  			s->lzma.len = MATCH_LEN_MIN + LEN_LOW_SYMBOLS
  					+ LEN_MID_SYMBOLS;
  		}
  	}
  
  	s->lzma.len += rc_bittree(&s->rc, probs, limit) - limit;
  }
  
  /* Decode a match. The distance will be stored in s->lzma.rep0. */
  static void INIT lzma_match(struct xz_dec_lzma2 *s, uint32_t pos_state)
  {
  	uint16_t *probs;
  	uint32_t dist_slot;
  	uint32_t limit;
  
  	lzma_state_match(&s->lzma.state);
  
  	s->lzma.rep3 = s->lzma.rep2;
  	s->lzma.rep2 = s->lzma.rep1;
  	s->lzma.rep1 = s->lzma.rep0;
  
  	lzma_len(s, &s->lzma.match_len_dec, pos_state);
  
  	probs = s->lzma.dist_slot[lzma_get_dist_state(s->lzma.len)];
  	dist_slot = rc_bittree(&s->rc, probs, DIST_SLOTS) - DIST_SLOTS;
  
  	if (dist_slot < DIST_MODEL_START) {
  		s->lzma.rep0 = dist_slot;
  	} else {
  		limit = (dist_slot >> 1) - 1;
  		s->lzma.rep0 = 2 + (dist_slot & 1);
  
  		if (dist_slot < DIST_MODEL_END) {
  			s->lzma.rep0 <<= limit;
  			probs = s->lzma.dist_special + s->lzma.rep0
  					- dist_slot - 1;
  			rc_bittree_reverse(&s->rc, probs,
  					&s->lzma.rep0, limit);
  		} else {
  			rc_direct(&s->rc, &s->lzma.rep0, limit - ALIGN_BITS);
  			s->lzma.rep0 <<= ALIGN_BITS;
  			rc_bittree_reverse(&s->rc, s->lzma.dist_align,
  					&s->lzma.rep0, ALIGN_BITS);
  		}
  	}
  }
  
  /*
   * Decode a repeated match. The distance is one of the four most recently
   * seen matches. The distance will be stored in s->lzma.rep0.
   */
  static void INIT lzma_rep_match(struct xz_dec_lzma2 *s, uint32_t pos_state)
  {
  	uint32_t tmp;
  
  	if (!rc_bit(&s->rc, &s->lzma.is_rep0[s->lzma.state])) {
  		if (!rc_bit(&s->rc, &s->lzma.is_rep0_long[
  				s->lzma.state][pos_state])) {
  			lzma_state_short_rep(&s->lzma.state);
  			s->lzma.len = 1;
  			return;
  		}
  	} else {
  		if (!rc_bit(&s->rc, &s->lzma.is_rep1[s->lzma.state])) {
  			tmp = s->lzma.rep1;
  		} else {
  			if (!rc_bit(&s->rc, &s->lzma.is_rep2[s->lzma.state])) {
  				tmp = s->lzma.rep2;
  			} else {
  				tmp = s->lzma.rep3;
  				s->lzma.rep3 = s->lzma.rep2;
  			}
  
  			s->lzma.rep2 = s->lzma.rep1;
  		}
  
  		s->lzma.rep1 = s->lzma.rep0;
  		s->lzma.rep0 = tmp;
  	}
  
  	lzma_state_long_rep(&s->lzma.state);
  	lzma_len(s, &s->lzma.rep_len_dec, pos_state);
  }
  
  /* LZMA decoder core */
  static bool_t INIT lzma_main(struct xz_dec_lzma2 *s)
  {
  	uint32_t pos_state;
  
  	/*
  	 * If the dictionary was reached during the previous call, try to
  	 * finish the possibly pending repeat in the dictionary.
  	 */
  	if (dict_has_space(&s->dict) && s->lzma.len > 0)
  		dict_repeat(&s->dict, &s->lzma.len, s->lzma.rep0);
  
  	/*
  	 * Decode more LZMA symbols. One iteration may consume up to
  	 * LZMA_IN_REQUIRED - 1 bytes.
  	 */
  	while (dict_has_space(&s->dict) && !rc_limit_exceeded(&s->rc)) {
  		pos_state = s->dict.pos & s->lzma.pos_mask;
  
  		if (!rc_bit(&s->rc, &s->lzma.is_match[
  				s->lzma.state][pos_state])) {
  			lzma_literal(s);
  		} else {
  			if (rc_bit(&s->rc, &s->lzma.is_rep[s->lzma.state]))
  				lzma_rep_match(s, pos_state);
  			else
  				lzma_match(s, pos_state);
  
  			if (!dict_repeat(&s->dict, &s->lzma.len, s->lzma.rep0))
  				return false;
  		}
  	}
  
  	/*
  	 * Having the range decoder always normalized when we are outside
  	 * this function makes it easier to correctly handle end of the chunk.
  	 */
  	rc_normalize(&s->rc);
  
  	return true;
  }
  
  /*
   * Reset the LZMA decoder and range decoder state. Dictionary is nore reset
   * here, because LZMA state may be reset without resetting the dictionary.
   */
  static void INIT lzma_reset(struct xz_dec_lzma2 *s)
  {
  	uint16_t *probs;
  	size_t i;
  
  	s->lzma.state = STATE_LIT_LIT;
  	s->lzma.rep0 = 0;
  	s->lzma.rep1 = 0;
  	s->lzma.rep2 = 0;
  	s->lzma.rep3 = 0;
  
  	/*
  	 * All probabilities are initialized to the same value. This hack
  	 * makes the code smaller by avoiding a separate loop for each
  	 * probability array.
  	 *
  	 * This could be optimized so that only that part of literal
  	 * probabilities that are actually required. In the common case
  	 * we would write 12 KiB less.
  	 */
  	probs = s->lzma.is_match[0];
  	for (i = 0; i < PROBS_TOTAL; ++i)
  		probs[i] = RC_BIT_MODEL_TOTAL / 2;
  
  	rc_reset(&s->rc);
  }
  
  /*
   * Decode and validate LZMA properties (lc/lp/pb) and calculate the bit masks
   * from the decoded lp and pb values. On success, the LZMA decoder state is
   * reset and true is returned.
   */
  static bool_t INIT lzma_props(struct xz_dec_lzma2 *s, uint8_t props)
  {
  	if (props > (4 * 5 + 4) * 9 + 8)
  		return false;
  
  	s->lzma.pos_mask = 0;
  	while (props >= 9 * 5) {
  		props -= 9 * 5;
  		++s->lzma.pos_mask;
  	}
  
  	s->lzma.pos_mask = (1 << s->lzma.pos_mask) - 1;
  
  	s->lzma.literal_pos_mask = 0;
  	while (props >= 9) {
  		props -= 9;
  		++s->lzma.literal_pos_mask;
  	}
  
  	s->lzma.lc = props;
  
  	if (s->lzma.lc + s->lzma.literal_pos_mask > 4)
  		return false;
  
  	s->lzma.literal_pos_mask = (1 << s->lzma.literal_pos_mask) - 1;
  
  	lzma_reset(s);
  
  	return true;
  }
  
  /*********
   * LZMA2 *
   *********/
  
  /*
   * The LZMA decoder assumes that if the input limit (s->rc.in_limit) hasn't
   * been exceeded, it is safe to read up to LZMA_IN_REQUIRED bytes. This
   * wrapper function takes care of making the LZMA decoder's assumption safe.
   *
   * As long as there is plenty of input left to be decoded in the current LZMA
   * chunk, we decode directly from the caller-supplied input buffer until
   * there's LZMA_IN_REQUIRED bytes left. Those remaining bytes are copied into
   * s->temp.buf, which (hopefully) gets filled on the next call to this
   * function. We decode a few bytes from the temporary buffer so that we can
   * continue decoding from the caller-supplied input buffer again.
   */
  static bool_t INIT lzma2_lzma(struct xz_dec_lzma2 *s, struct xz_buf *b)
  {
  	size_t in_avail;
  	uint32_t tmp;
  
  	in_avail = b->in_size - b->in_pos;
  	if (s->temp.size > 0 || s->lzma2.compressed == 0) {
  		tmp = 2 * LZMA_IN_REQUIRED - s->temp.size;
  		if (tmp > s->lzma2.compressed - s->temp.size)
  			tmp = s->lzma2.compressed - s->temp.size;
  		if (tmp > in_avail)
  			tmp = in_avail;
  
  		memcpy(s->temp.buf + s->temp.size, b->in + b->in_pos, tmp);
  
  		if (s->temp.size + tmp == s->lzma2.compressed) {
  			memzero(s->temp.buf + s->temp.size + tmp,
  					sizeof(s->temp.buf)
  						- s->temp.size - tmp);
  			s->rc.in_limit = s->temp.size + tmp;
  		} else if (s->temp.size + tmp < LZMA_IN_REQUIRED) {
  			s->temp.size += tmp;
  			b->in_pos += tmp;
  			return true;
  		} else {
  			s->rc.in_limit = s->temp.size + tmp - LZMA_IN_REQUIRED;
  		}
  
  		s->rc.in = s->temp.buf;
  		s->rc.in_pos = 0;
  
  		if (!lzma_main(s) || s->rc.in_pos > s->temp.size + tmp)
  			return false;
  
  		s->lzma2.compressed -= s->rc.in_pos;
  
  		if (s->rc.in_pos < s->temp.size) {
  			s->temp.size -= s->rc.in_pos;
  			memmove(s->temp.buf, s->temp.buf + s->rc.in_pos,
  					s->temp.size);
  			return true;
  		}
  
  		b->in_pos += s->rc.in_pos - s->temp.size;
  		s->temp.size = 0;
  	}
  
  	in_avail = b->in_size - b->in_pos;
  	if (in_avail >= LZMA_IN_REQUIRED) {
  		s->rc.in = b->in;
  		s->rc.in_pos = b->in_pos;
  
  		if (in_avail >= s->lzma2.compressed + LZMA_IN_REQUIRED)
  			s->rc.in_limit = b->in_pos + s->lzma2.compressed;
  		else
  			s->rc.in_limit = b->in_size - LZMA_IN_REQUIRED;
  
  		if (!lzma_main(s))
  			return false;
  
  		in_avail = s->rc.in_pos - b->in_pos;
  		if (in_avail > s->lzma2.compressed)
  			return false;
  
  		s->lzma2.compressed -= in_avail;
  		b->in_pos = s->rc.in_pos;
  	}
  
  	in_avail = b->in_size - b->in_pos;
  	if (in_avail < LZMA_IN_REQUIRED) {
  		if (in_avail > s->lzma2.compressed)
  			in_avail = s->lzma2.compressed;
  
  		memcpy(s->temp.buf, b->in + b->in_pos, in_avail);
  		s->temp.size = in_avail;
  		b->in_pos += in_avail;
  	}
  
  	return true;
  }
  
  /*
   * Take care of the LZMA2 control layer, and forward the job of actual LZMA
   * decoding or copying of uncompressed chunks to other functions.
   */
  XZ_EXTERN enum xz_ret INIT xz_dec_lzma2_run(struct xz_dec_lzma2 *s,
  					    struct xz_buf *b)
  {
  	uint32_t tmp;
  
  	while (b->in_pos < b->in_size || s->lzma2.sequence == SEQ_LZMA_RUN) {
  		switch (s->lzma2.sequence) {
  		case SEQ_CONTROL:
  			/*
  			 * LZMA2 control byte
  			 *
  			 * Exact values:
  			 *   0x00   End marker
  			 *   0x01   Dictionary reset followed by
  			 *          an uncompressed chunk
  			 *   0x02   Uncompressed chunk (no dictionary reset)
  			 *
  			 * Highest three bits (s->control & 0xE0):
  			 *   0xE0   Dictionary reset, new properties and state
  			 *          reset, followed by LZMA compressed chunk
  			 *   0xC0   New properties and state reset, followed
  			 *          by LZMA compressed chunk (no dictionary
  			 *          reset)
  			 *   0xA0   State reset using old properties,
  			 *          followed by LZMA compressed chunk (no
  			 *          dictionary reset)
  			 *   0x80   LZMA chunk (no dictionary or state reset)
  			 *
  			 * For LZMA compressed chunks, the lowest five bits
  			 * (s->control & 1F) are the highest bits of the
  			 * uncompressed size (bits 16-20).
  			 *
  			 * A new LZMA2 stream must begin with a dictionary
  			 * reset. The first LZMA chunk must set new
  			 * properties and reset the LZMA state.
  			 *
  			 * Values that don't match anything described above
  			 * are invalid and we return XZ_DATA_ERROR.
  			 */
  			tmp = b->in[b->in_pos++];
  
  			if (tmp == 0x00)
  				return XZ_STREAM_END;
  
  			if (tmp >= 0xE0 || tmp == 0x01) {
  				s->lzma2.need_props = true;
  				s->lzma2.need_dict_reset = false;
  				dict_reset(&s->dict, b);
  			} else if (s->lzma2.need_dict_reset) {
  				return XZ_DATA_ERROR;
  			}
  
  			if (tmp >= 0x80) {
  				s->lzma2.uncompressed = (tmp & 0x1F) << 16;
  				s->lzma2.sequence = SEQ_UNCOMPRESSED_1;
  
  				if (tmp >= 0xC0) {
  					/*
  					 * When there are new properties,
  					 * state reset is done at
  					 * SEQ_PROPERTIES.
  					 */
  					s->lzma2.need_props = false;
  					s->lzma2.next_sequence
  							= SEQ_PROPERTIES;
  
  				} else if (s->lzma2.need_props) {
  					return XZ_DATA_ERROR;
  
  				} else {
  					s->lzma2.next_sequence
  							= SEQ_LZMA_PREPARE;
  					if (tmp >= 0xA0)
  						lzma_reset(s);
  				}
  			} else {
  				if (tmp > 0x02)
  					return XZ_DATA_ERROR;
  
  				s->lzma2.sequence = SEQ_COMPRESSED_0;
  				s->lzma2.next_sequence = SEQ_COPY;
  			}
  
  			break;
  
  		case SEQ_UNCOMPRESSED_1:
  			s->lzma2.uncompressed
  					+= (uint32_t)b->in[b->in_pos++] << 8;
  			s->lzma2.sequence = SEQ_UNCOMPRESSED_2;
  			break;
  
  		case SEQ_UNCOMPRESSED_2:
  			s->lzma2.uncompressed
  					+= (uint32_t)b->in[b->in_pos++] + 1;
  			s->lzma2.sequence = SEQ_COMPRESSED_0;
  			break;
  
  		case SEQ_COMPRESSED_0:
  			s->lzma2.compressed
  					= (uint32_t)b->in[b->in_pos++] << 8;
  			s->lzma2.sequence = SEQ_COMPRESSED_1;
  			break;
  
  		case SEQ_COMPRESSED_1:
  			s->lzma2.compressed
  					+= (uint32_t)b->in[b->in_pos++] + 1;
  			s->lzma2.sequence = s->lzma2.next_sequence;
  			break;
  
  		case SEQ_PROPERTIES:
  			if (!lzma_props(s, b->in[b->in_pos++]))
  				return XZ_DATA_ERROR;
  
  			s->lzma2.sequence = SEQ_LZMA_PREPARE;
  
  		/* Fall through */
  
  		case SEQ_LZMA_PREPARE:
  			if (s->lzma2.compressed < RC_INIT_BYTES)
  				return XZ_DATA_ERROR;
  
  			if (!rc_read_init(&s->rc, b))
  				return XZ_OK;
  
  			s->lzma2.compressed -= RC_INIT_BYTES;
  			s->lzma2.sequence = SEQ_LZMA_RUN;
  
  		/* Fall through */
  
  		case SEQ_LZMA_RUN:
  			/*
  			 * Set dictionary limit to indicate how much we want
  			 * to be encoded at maximum. Decode new data into the
  			 * dictionary. Flush the new data from dictionary to
  			 * b->out. Check if we finished decoding this chunk.
  			 * In case the dictionary got full but we didn't fill
  			 * the output buffer yet, we may run this loop
  			 * multiple times without changing s->lzma2.sequence.
  			 */
  			dict_limit(&s->dict, min_t(size_t,
  					b->out_size - b->out_pos,
  					s->lzma2.uncompressed));
  			if (!lzma2_lzma(s, b))
  				return XZ_DATA_ERROR;
  
  			s->lzma2.uncompressed -= dict_flush(&s->dict, b);
  
  			if (s->lzma2.uncompressed == 0) {
  				if (s->lzma2.compressed > 0 || s->lzma.len > 0
  						|| !rc_is_finished(&s->rc))
  					return XZ_DATA_ERROR;
  
  				rc_reset(&s->rc);
  				s->lzma2.sequence = SEQ_CONTROL;
  
  			} else if (b->out_pos == b->out_size
  					|| (b->in_pos == b->in_size
  						&& s->temp.size
  						< s->lzma2.compressed)) {
  				return XZ_OK;
  			}
  
  			break;
  
  		case SEQ_COPY:
  			dict_uncompressed(&s->dict, b, &s->lzma2.compressed);
  			if (s->lzma2.compressed > 0)
  				return XZ_OK;
  
  			s->lzma2.sequence = SEQ_CONTROL;
  			break;
  		}
  	}
  
  	return XZ_OK;
  }
  
  XZ_EXTERN struct xz_dec_lzma2 *INIT xz_dec_lzma2_create(enum xz_mode mode,
  						   uint32_t dict_max)
  {
  	struct xz_dec_lzma2 *s = malloc(sizeof(*s));
  	if (s == NULL)
  		return NULL;
  
  	s->dict.mode = mode;
  	s->dict.size_max = dict_max;
  
  	if (DEC_IS_PREALLOC(mode)) {
  		s->dict.buf = large_malloc(dict_max);
  		if (s->dict.buf == NULL) {
  			free(s);
  			return NULL;
  		}
  	} else if (DEC_IS_DYNALLOC(mode)) {
  		s->dict.buf = NULL;
  		s->dict.allocated = 0;
  	}
  
  	return s;
  }
  
  XZ_EXTERN enum xz_ret INIT xz_dec_lzma2_reset(struct xz_dec_lzma2 *s, uint8_t props)
  {
  	/* This limits dictionary size to 3 GiB to keep parsing simpler. */
  	if (props > 39)
  		return XZ_OPTIONS_ERROR;
  
  	s->dict.size = 2 + (props & 1);
  	s->dict.size <<= (props >> 1) + 11;
  
  	if (DEC_IS_MULTI(s->dict.mode)) {
  		if (s->dict.size > s->dict.size_max)
  			return XZ_MEMLIMIT_ERROR;
  
  		s->dict.end = s->dict.size;
  
  		if (DEC_IS_DYNALLOC(s->dict.mode)) {
  			if (s->dict.allocated < s->dict.size) {
  				large_free(s->dict.buf);
  				s->dict.buf = large_malloc(s->dict.size);
  				if (s->dict.buf == NULL) {
  					s->dict.allocated = 0;
  					return XZ_MEM_ERROR;
  				}
  			}
  		}
  	}
  
  	s->lzma.len = 0;
  
  	s->lzma2.sequence = SEQ_CONTROL;
  	s->lzma2.need_dict_reset = true;
  
  	s->temp.size = 0;
  
  	return XZ_OK;
  }
  
  XZ_EXTERN void INIT xz_dec_lzma2_end(struct xz_dec_lzma2 *s)
  {
  	if (DEC_IS_MULTI(s->dict.mode))
  		large_free(s->dict.buf);
  
  	free(s);
  }
  