deflate_medium.c - third_party/github.com/zlib-ng/zlib-ng - Git at Google

 /* deflate_medium.c -- The deflate_medium deflate strategy
  *
  * Copyright (C) 2013 Intel Corporation. All rights reserved.
  * Authors:
  *  Arjan van de Ven    <arjan@linux.intel.com>
  *
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
 #ifndef NO_MEDIUM_STRATEGY
 #include "zbuild.h"
 #include "deflate.h"
 #include "deflate_p.h"
 #include "functable.h"
 #include "insert_string_p.h"

 struct match {
     uint16_t match_start;
     uint16_t match_length;
     uint16_t strstart;
     uint16_t orgstart;
 };

 static int emit_match(deflate_state *s, unsigned char *window, struct match match) {
     int bflush = 0;
     uint32_t match_len = match.match_length;

     /* None of the below functions care about s->lookahead, so decrement it early */
     s->lookahead -= match_len;

     /* matches that are not long enough we need to emit as literals */
     if (match_len < WANT_MIN_MATCH) {
         while (match_len) {
             bflush += zng_tr_tally_lit(s, window[match.strstart]);
             match_len--;
             match.strstart++;
         }
         return bflush;
     }

     check_match(s, match.strstart, match.match_start, match_len);

     bflush += zng_tr_tally_dist(s, match.strstart - match.match_start, match_len - STD_MIN_MATCH);
     return bflush;
 }

 /* insert_match assumes: s->lookahead > match.match_length + WANT_MIN_MATCH */
 static void insert_match(deflate_state *s, unsigned char *window, struct match match) {
     uint32_t match_len = match.match_length;
     uint32_t strstart = match.strstart;

     /* matches that are not long enough we need to emit as literals */
     if (LIKELY(match_len < WANT_MIN_MATCH)) {
         strstart++;
         match_len--;
         if (UNLIKELY(match_len > 0)) {
             if (strstart >= match.orgstart) {
                 if (strstart + match_len - 1 >= match.orgstart) {
                     insert_string(s, window, strstart, match_len);
                 } else {
                     insert_string(s, window, strstart, match.orgstart - strstart + 1);
                 }
             }
         }
         return;
     }

     /* Insert new strings in the hash table only if the match length
      * is not too large. This saves time but degrades compression.
      */
     if (match_len <= 16 * s->max_insert_length && s->lookahead >= WANT_MIN_MATCH) {
         match_len--; /* string at strstart already in table */
         strstart++;

         if (LIKELY(strstart >= match.orgstart)) {
             if (LIKELY(strstart + match_len - 1 >= match.orgstart)) {
                 insert_string(s, window, strstart, match_len);
             } else {
                 insert_string(s, window, strstart, match.orgstart - strstart + 1);
             }
         } else if (match.orgstart < strstart + match_len) {
             insert_string(s, window, match.orgstart, strstart + match_len - match.orgstart);
         }
     } else {
         strstart += match_len;
         quick_insert_string(s, window, strstart + 2 - STD_MIN_MATCH);

         /* If lookahead < WANT_MIN_MATCH, ins_h is garbage, but it does not
          * matter since it will be recomputed at next deflate call.
          */
     }
 }

 Z_FORCEINLINE static struct match find_best_match(deflate_state *s, uint32_t hash_head) {
     struct match m;
     int64_t dist;

     m.strstart = (uint16_t)s->strstart;
     m.orgstart = m.strstart;

     dist = (int64_t)s->strstart - hash_head;
     if (dist <= MAX_DIST(s) && dist > 0 && hash_head != 0) {
         /* To simplify the code, we prevent matches with the string
          * of window index 0 (in particular we have to avoid a match
          * of the string with itself at the start of the input file).
          */
         m.match_length = (uint16_t)FUNCTABLE_CALL(longest_match)(s, hash_head);
         m.match_start = (uint16_t)s->match_start;
         if (UNLIKELY(m.match_length < WANT_MIN_MATCH))
             m.match_length = 1;
         if (UNLIKELY(m.match_start >= m.strstart)) {
             /* this can happen due to some restarts */
             m.match_length = 1;
         }
     } else {
         /* Set up the match to be a 1 byte literal */
         m.match_start = 0;
         m.match_length = 1;
     }

     return m;
 }

 /* fizzle_matches assumes:
  * - current->match_length > 1
  * - (current->match_length - 1) <= next->match_start
  * - (current->match_length - 1) <= next->strstart
  */
 static void fizzle_matches(deflate_state *s, unsigned char *window, struct match *current, struct match *next) {
     unsigned char *match, *orig;
     struct match c, n;
     int changed = 0;
     Pos limit;

     match = window - current->match_length + 1 + next->match_start;
     orig  = window - current->match_length + 1 + next->strstart;

     /* quick exit check.. if this fails then don't bother with anything else */
     if (LIKELY(*match != *orig))
         return;

     c = *current;
     n = *next;

     /* step one: try to move the "next" match to the left as much as possible */
     limit = next->strstart > MAX_DIST(s) ? next->strstart - (Pos)MAX_DIST(s) : 0;

     match = window + n.match_start - 1;
     orig = window + n.strstart - 1;

     while (*match == *orig) {
         if (UNLIKELY(c.match_length < 1))
             break;
         if (UNLIKELY(n.strstart <= limit))
             break;
         if (UNLIKELY(n.match_length >= 256))
             break;
         if (UNLIKELY(n.match_start <= 1))
             break;

         n.strstart--;
         n.match_start--;
         n.match_length++;
         c.match_length--;
         match--;
         orig--;
         changed++;
     }

     if (changed && c.match_length <= 1 && n.match_length != 2) {
         n.orgstart++;
         *current = c;
         *next = n;
     } else {
         return;
     }
 }

 Z_INTERNAL block_state deflate_medium(deflate_state *s, int flush) {
     /* Align the first struct to start on a new cacheline, this allows us to fit both structs in one cacheline */
     ALIGNED_(16) struct match current_match = {0};
                  struct match next_match = {0};
     unsigned char *window = s->window;

     /* For levels below 5, don't check the next position for a better match */
     int early_exit = s->level < 5;

     for (;;) {
         uint32_t hash_head = 0;    /* head of the hash chain */
         int bflush = 0;       /* set if current block must be flushed */

         /* Make sure that we always have enough lookahead, except
          * at the end of the input file. We need STD_MAX_MATCH bytes
          * for the next match, plus WANT_MIN_MATCH bytes to insert the
          * string following the next current_match.
          */
         if (s->lookahead < MIN_LOOKAHEAD) {
             PREFIX(fill_window)(s);
             if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
                 return need_more;
             }
             if (UNLIKELY(s->lookahead == 0))
                 break; /* flush the current block */
             next_match.match_length = 0;
         }

         /* Insert the string window[strstart .. strstart+2] in the
          * dictionary, and set hash_head to the head of the hash chain:
          */

         /* If we already have a future match from a previous round, just use that */
         if (!early_exit && next_match.match_length > 0) {
             current_match = next_match;
             next_match.match_length = 0;
         } else {
             hash_head = 0;
             if (s->lookahead >= WANT_MIN_MATCH) {
                 hash_head = quick_insert_string(s, window, s->strstart);
             }

             current_match = find_best_match(s, hash_head);
         }

         if (LIKELY(s->lookahead > (unsigned int)(current_match.match_length + WANT_MIN_MATCH)))
             insert_match(s, window, current_match);

         /* now, look ahead one */
         if (LIKELY(!early_exit && s->lookahead > MIN_LOOKAHEAD && (uint32_t)(current_match.strstart + current_match.match_length) < (s->window_size - MIN_LOOKAHEAD))) {
             s->strstart = current_match.strstart + current_match.match_length;
             hash_head = quick_insert_string(s, window, s->strstart);

             next_match = find_best_match(s, hash_head);

             uint32_t tmp_cmatch_len_sub = current_match.match_length - 1;
             if (tmp_cmatch_len_sub
                      && next_match.match_length >= WANT_MIN_MATCH
                      && tmp_cmatch_len_sub <= next_match.match_start
                      && tmp_cmatch_len_sub <= next_match.strstart) {
                 fizzle_matches(s, window, &current_match, &next_match);
             }

             s->strstart = current_match.strstart;
         } else {
             next_match.match_length = 0;
         }

         /* now emit the current match */
         bflush = emit_match(s, window, current_match);

         /* move the "cursor" forward */
         s->strstart += current_match.match_length;

         if (UNLIKELY(bflush))
             FLUSH_BLOCK(s, window, 0);
     }
     s->insert = s->strstart < (STD_MIN_MATCH - 1) ? s->strstart : (STD_MIN_MATCH - 1);
     if (flush == Z_FINISH) {
         FLUSH_BLOCK(s, window, 1);
         return finish_done;
     }
     if (UNLIKELY(s->sym_next))
         FLUSH_BLOCK(s, window, 0);

     return block_done;
 }
 #endif
	/* deflate_medium.c -- The deflate_medium deflate strategy
	*
	* Copyright (C) 2013 Intel Corporation. All rights reserved.
	* Authors:
	* Arjan van de Ven <arjan@linux.intel.com>
	*
	* For conditions of distribution and use, see copyright notice in zlib.h
	*/
	#ifndef NO_MEDIUM_STRATEGY
	#include "zbuild.h"
	#include "deflate.h"
	#include "deflate_p.h"
	#include "functable.h"
	#include "insert_string_p.h"

	struct match {
	uint16_t match_start;
	uint16_t match_length;
	uint16_t strstart;
	uint16_t orgstart;
	};

	static int emit_match(deflate_state s, unsigned char window, struct match match) {
	int bflush = 0;
	uint32_t match_len = match.match_length;

	/* None of the below functions care about s->lookahead, so decrement it early */
	s->lookahead -= match_len;

	/* matches that are not long enough we need to emit as literals */
	if (match_len < WANT_MIN_MATCH) {
	while (match_len) {
	bflush += zng_tr_tally_lit(s, window[match.strstart]);
	match_len--;
	match.strstart++;
	}
	return bflush;
	}

	check_match(s, match.strstart, match.match_start, match_len);

	bflush += zng_tr_tally_dist(s, match.strstart - match.match_start, match_len - STD_MIN_MATCH);
	return bflush;
	}

	/* insert_match assumes: s->lookahead > match.match_length + WANT_MIN_MATCH */
	static void insert_match(deflate_state s, unsigned char window, struct match match) {
	uint32_t match_len = match.match_length;
	uint32_t strstart = match.strstart;

	/* matches that are not long enough we need to emit as literals */
	if (LIKELY(match_len < WANT_MIN_MATCH)) {
	strstart++;
	match_len--;
	if (UNLIKELY(match_len > 0)) {
	if (strstart >= match.orgstart) {
	if (strstart + match_len - 1 >= match.orgstart) {
	insert_string(s, window, strstart, match_len);
	} else {
	insert_string(s, window, strstart, match.orgstart - strstart + 1);
	}
	}
	}
	return;
	}

	/* Insert new strings in the hash table only if the match length
	* is not too large. This saves time but degrades compression.
	*/
	if (match_len <= 16 * s->max_insert_length && s->lookahead >= WANT_MIN_MATCH) {
	match_len--; /* string at strstart already in table */
	strstart++;

	if (LIKELY(strstart >= match.orgstart)) {
	if (LIKELY(strstart + match_len - 1 >= match.orgstart)) {
	insert_string(s, window, strstart, match_len);
	} else {
	insert_string(s, window, strstart, match.orgstart - strstart + 1);
	}
	} else if (match.orgstart < strstart + match_len) {
	insert_string(s, window, match.orgstart, strstart + match_len - match.orgstart);
	}
	} else {
	strstart += match_len;
	quick_insert_string(s, window, strstart + 2 - STD_MIN_MATCH);

	/* If lookahead < WANT_MIN_MATCH, ins_h is garbage, but it does not
	* matter since it will be recomputed at next deflate call.
	*/
	}
	}

	Z_FORCEINLINE static struct match find_best_match(deflate_state *s, uint32_t hash_head) {
	struct match m;
	int64_t dist;

	m.strstart = (uint16_t)s->strstart;
	m.orgstart = m.strstart;

	dist = (int64_t)s->strstart - hash_head;
	if (dist <= MAX_DIST(s) && dist > 0 && hash_head != 0) {
	/* To simplify the code, we prevent matches with the string
	* of window index 0 (in particular we have to avoid a match
	* of the string with itself at the start of the input file).
	*/
	m.match_length = (uint16_t)FUNCTABLE_CALL(longest_match)(s, hash_head);
	m.match_start = (uint16_t)s->match_start;
	if (UNLIKELY(m.match_length < WANT_MIN_MATCH))
	m.match_length = 1;
	if (UNLIKELY(m.match_start >= m.strstart)) {
	/* this can happen due to some restarts */
	m.match_length = 1;
	}
	} else {
	/* Set up the match to be a 1 byte literal */
	m.match_start = 0;
	m.match_length = 1;
	}

	return m;
	}

	/* fizzle_matches assumes:
	* - current->match_length > 1
	* - (current->match_length - 1) <= next->match_start
	* - (current->match_length - 1) <= next->strstart
	*/
	static void fizzle_matches(deflate_state s, unsigned char window, struct match current, struct match next) {
	unsigned char match, orig;
	struct match c, n;
	int changed = 0;
	Pos limit;

	match = window - current->match_length + 1 + next->match_start;
	orig = window - current->match_length + 1 + next->strstart;

	/* quick exit check.. if this fails then don't bother with anything else */
	if (LIKELY(match != orig))
	return;

	c = *current;
	n = *next;

	/* step one: try to move the "next" match to the left as much as possible */
	limit = next->strstart > MAX_DIST(s) ? next->strstart - (Pos)MAX_DIST(s) : 0;

	match = window + n.match_start - 1;
	orig = window + n.strstart - 1;

	while (match == orig) {
	if (UNLIKELY(c.match_length < 1))
	break;
	if (UNLIKELY(n.strstart <= limit))
	break;
	if (UNLIKELY(n.match_length >= 256))
	break;
	if (UNLIKELY(n.match_start <= 1))
	break;

	n.strstart--;
	n.match_start--;
	n.match_length++;
	c.match_length--;
	match--;
	orig--;
	changed++;
	}

	if (changed && c.match_length <= 1 && n.match_length != 2) {
	n.orgstart++;
	*current = c;
	*next = n;
	} else {
	return;
	}
	}

	Z_INTERNAL block_state deflate_medium(deflate_state *s, int flush) {
	/* Align the first struct to start on a new cacheline, this allows us to fit both structs in one cacheline */
	ALIGNED_(16) struct match current_match = {0};
	struct match next_match = {0};
	unsigned char *window = s->window;

	/* For levels below 5, don't check the next position for a better match */
	int early_exit = s->level < 5;

	for (;;) {
	uint32_t hash_head = 0; /* head of the hash chain */
	int bflush = 0; /* set if current block must be flushed */

	/* Make sure that we always have enough lookahead, except
	* at the end of the input file. We need STD_MAX_MATCH bytes
	* for the next match, plus WANT_MIN_MATCH bytes to insert the
	* string following the next current_match.
	*/
	if (s->lookahead < MIN_LOOKAHEAD) {
	PREFIX(fill_window)(s);
	if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
	return need_more;
	}
	if (UNLIKELY(s->lookahead == 0))
	break; /* flush the current block */
	next_match.match_length = 0;
	}

	/* Insert the string window[strstart .. strstart+2] in the
	* dictionary, and set hash_head to the head of the hash chain:
	*/

	/* If we already have a future match from a previous round, just use that */
	if (!early_exit && next_match.match_length > 0) {
	current_match = next_match;
	next_match.match_length = 0;
	} else {
	hash_head = 0;
	if (s->lookahead >= WANT_MIN_MATCH) {
	hash_head = quick_insert_string(s, window, s->strstart);
	}

	current_match = find_best_match(s, hash_head);
	}

	if (LIKELY(s->lookahead > (unsigned int)(current_match.match_length + WANT_MIN_MATCH)))
	insert_match(s, window, current_match);

	/* now, look ahead one */
	if (LIKELY(!early_exit && s->lookahead > MIN_LOOKAHEAD && (uint32_t)(current_match.strstart + current_match.match_length) < (s->window_size - MIN_LOOKAHEAD))) {
	s->strstart = current_match.strstart + current_match.match_length;
	hash_head = quick_insert_string(s, window, s->strstart);

	next_match = find_best_match(s, hash_head);

	uint32_t tmp_cmatch_len_sub = current_match.match_length - 1;
	if (tmp_cmatch_len_sub
	&& next_match.match_length >= WANT_MIN_MATCH
	&& tmp_cmatch_len_sub <= next_match.match_start
	&& tmp_cmatch_len_sub <= next_match.strstart) {
	fizzle_matches(s, window, &current_match, &next_match);
	}

	s->strstart = current_match.strstart;
	} else {
	next_match.match_length = 0;
	}

	/* now emit the current match */
	bflush = emit_match(s, window, current_match);

	/* move the "cursor" forward */
	s->strstart += current_match.match_length;

	if (UNLIKELY(bflush))
	FLUSH_BLOCK(s, window, 0);
	}
	s->insert = s->strstart < (STD_MIN_MATCH - 1) ? s->strstart : (STD_MIN_MATCH - 1);
	if (flush == Z_FINISH) {
	FLUSH_BLOCK(s, window, 1);
	return finish_done;
	}
	if (UNLIKELY(s->sym_next))
	FLUSH_BLOCK(s, window, 0);

	return block_done;
	}
	#endif