deflate.c

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	Assert(window_size == (ulg)2*WSIZE, "no sliding with BIG_MEM");

	memcpy((char*)encoder->window, (char*)encoder->window+WSIZE, (unsigned)WSIZE);
	encoder->match_start -= WSIZE;
	encoder->strstart    -= WSIZE; /* we now have strstart >= MAX_DIST: */
	encoder->block_start -= (long) WSIZE;

	for(n = 0; n < HASH_SIZE; n++) {
	    m = head(n);
	    head(n) = (ush)(m >= WSIZE ? m-WSIZE : NIL);
	}
	for(n = 0; n < WSIZE; n++) {
	    m = encoder->prev[n];
	    encoder->prev[n] = (ush)(m >= WSIZE ? m-WSIZE : NIL);
	    /* If n is not on any hash chain, prev[n] is garbage but
	     * its value will never be used.
	     */
	}
	more += WSIZE;
    }
    /* At this point, more >= 2 */
    if(!encoder->eofile) {
	n = encoder->read_func((char*)encoder->window+encoder->strstart
			       + encoder->lookahead,
			       (long)more,
			       encoder->user_val);
	if(n == 0 || n == (unsigned)EOF) {
	    encoder->eofile = 1;
	} else {
	    encoder->lookahead += n;
	}
    }
}

/* ===========================================================================
 * Processes a new input file and return its compressed length. This
 * function does not perform lazy evaluationof matches and inserts
 * new strings in the dictionary only for unmatched strings or for short
 * matches. It is used only for the fast compression options.
 */
local void deflate_fast(DeflateHandler encoder)
{
/*
    encoder->prev_length = MIN_MATCH-1;
    encoder->match_length = 0;
*/
    while(encoder->lookahead != 0 && encoder->qhead == NULL) {
	int flush; /* set if current block must be flushed */

	/* Insert the string window[strstart .. strstart+2] in the
	 * dictionary, and set hash_head to the head of the hash chain:
	 */
	INSERT_STRING(encoder->strstart, encoder->hash_head);

	/* Find the longest match, discarding those <= prev_length.
	 * At this point we have always match_length < MIN_MATCH
	 */
	if(encoder->hash_head != NIL &&
	   encoder->strstart - encoder->hash_head <= MAX_DIST) {
	    /* 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).
	     */
	    encoder->match_length = longest_match(encoder, encoder->hash_head);
	    /* longest_match() sets match_start */
	    if(encoder->match_length > encoder->lookahead)
		encoder->match_length = encoder->lookahead;
	}
	if(encoder->match_length >= MIN_MATCH) {
	    check_match(encoder, encoder->strstart,
			encoder->match_start, encoder->match_length);

	    flush = ct_tally(encoder, encoder->strstart - encoder->match_start,
			     encoder->match_length - MIN_MATCH);

	    encoder->lookahead -= encoder->match_length;

	    /* Insert new strings in the hash table only if the match length
	     * is not too large. This saves time but degrades compression.
	     */
	    if(encoder->match_length <= encoder->max_lazy_match) {
		encoder->match_length--; /* string at strstart already in hash table */
		do {
		    encoder->strstart++;
		    INSERT_STRING(encoder->strstart, encoder->hash_head);
		    /* strstart never exceeds WSIZE-MAX_MATCH, so there are
		     * always MIN_MATCH bytes ahead. If lookahead < MIN_MATCH
		     * these bytes are garbage, but it does not matter since
		     * the next lookahead bytes will be emitted as literals.
		     */
		} while(--encoder->match_length != 0);
		encoder->strstart++;
	    } else {
		encoder->strstart += encoder->match_length;
		encoder->match_length = 0;
		encoder->ins_h = encoder->window[encoder->strstart];
		UPDATE_HASH(encoder->ins_h,
			    encoder->window[encoder->strstart + 1]);
#if MIN_MATCH != 3
		Call UPDATE_HASH() MIN_MATCH-3 more times
#endif
	    }
	} else {
	    /* No match, output a literal byte */
	    Tracevv((stderr,"%c",encoder->window[encoder->strstart]));
	    flush = ct_tally (encoder, 0, encoder->window[encoder->strstart]);
	    encoder->lookahead--;
	    encoder->strstart++;
	}
	if(flush)
	{
	    flush_block(encoder, 0);
	    encoder->block_start = (long)encoder->strstart;
	}

	/* Make sure that we always have enough lookahead, except
	 * at the end of the input file. We need MAX_MATCH bytes
	 * for the next match, plus MIN_MATCH bytes to insert the
	 * string following the next match.
	 */
	while(encoder->lookahead < MIN_LOOKAHEAD && !encoder->eofile)
	    fill_window(encoder);
    }
}

local void deflate_better(DeflateHandler encoder) {
    /* Process the input block. */
    while(encoder->lookahead != 0 && encoder->qhead == NULL) {
	/* Insert the string window[strstart .. strstart+2] in the
	 * dictionary, and set hash_head to the head of the hash chain:
	 */
	INSERT_STRING(encoder->strstart, encoder->hash_head);

	/* Find the longest match, discarding those <= prev_length.
	 */
	encoder->prev_length = encoder->match_length;
	encoder->prev_match = encoder->match_start;
	encoder->match_length = MIN_MATCH-1;

	if(encoder->hash_head != NIL &&
	   encoder->prev_length < encoder->max_lazy_match &&
	   encoder->strstart - encoder->hash_head <= MAX_DIST) {
	    /* 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).
	     */
	    encoder->match_length = longest_match(encoder, encoder->hash_head);
	    /* longest_match() sets match_start */
	    if(encoder->match_length > encoder->lookahead)
		encoder->match_length = encoder->lookahead;

	    /* Ignore a length 3 match if it is too distant: */
	    if(encoder->match_length == MIN_MATCH &&
		encoder->strstart - encoder->match_start > TOO_FAR){
		/* If prev_match is also MIN_MATCH, match_start is garbage
		 * but we will ignore the current match anyway.
		 */
		encoder->match_length--;
	    }
	}
	/* If there was a match at the previous step and the current
	 * match is not better, output the previous match:
	 */
	if(encoder->prev_length >= MIN_MATCH &&
	   encoder->match_length <= encoder->prev_length) {
	    int flush; /* set if current block must be flushed */

	    check_match(encoder, encoder->strstart-1,
			encoder->prev_match, encoder->prev_length);

	    flush = ct_tally(encoder, encoder->strstart-1-encoder->prev_match,
			     encoder->prev_length - MIN_MATCH);

	    /* Insert in hash table all strings up to the end of the match.
	     * strstart-1 and strstart are already inserted.
	     */
	    encoder->lookahead -= encoder->prev_length-1;
	    encoder->prev_length -= 2;
	    do {
		encoder->strstart++;
		INSERT_STRING(encoder->strstart, encoder->hash_head);
		/* strstart never exceeds WSIZE-MAX_MATCH, so there are
		 * always MIN_MATCH bytes ahead. If lookahead < MIN_MATCH
		 * these bytes are garbage, but it does not matter since the
		 * next lookahead bytes will always be emitted as literals.
		 */
	    } while(--encoder->prev_length != 0);
	    encoder->match_available = 0;
	    encoder->match_length = MIN_MATCH-1;
	    encoder->strstart++;
	    if(flush) {
		flush_block(encoder, 0);
		encoder->block_start = (long)encoder->strstart;
	    }

	} else if(encoder->match_available) {
	    /* If there was no match at the previous position, output a
	     * single literal. If there was a match but the current match
	     * is longer, truncate the previous match to a single literal.
	     */
	    Tracevv((stderr,"%c",encoder->window[encoder->strstart-1]));
	    if(ct_tally (encoder, 0, encoder->window[encoder->strstart-1])) {
		flush_block(encoder, 0);
		encoder->block_start = (long)encoder->strstart;
	    }
	    encoder->strstart++;
	    encoder->lookahead--;
	} else {
	    /* There is no previous match to compare with, wait for
	     * the next step to decide.
	     */
	    encoder->match_available = 1;
	    encoder->strstart++;
	    encoder->lookahead--;
	}

	/* Make sure that we always have enough lookahead, except
	 * at the end of the input file. We need MAX_MATCH bytes
	 * for the next match, plus MIN_MATCH bytes to insert the
	 * string following the next match.
	 */
	while(encoder->lookahead < MIN_LOOKAHEAD && !encoder->eofile)
	    fill_window(encoder);
    }
}

/*ARGSUSED*/
static long default_read_func(char *buf, long size, void *v)
{
    return (long)fread(buf, 1, size, stdin);
}

DeflateHandler open_deflate_handler(
    long (* read_func)(char *buf, long size, void *user_val),
    void *user_val,
    int level)
{
    DeflateHandler encoder;

    if(level < 1 || level > 9)
	return NULL; /* error("bad compression level"); */

    encoder = (DeflateHandler)safe_malloc(sizeof(struct _DeflateHandler));
    if(encoder == NULL)
	return NULL;
    memset(encoder, 0, sizeof(struct _DeflateHandler));
    encoder->compr_level = level;
    if(read_func == NULL)
	encoder->read_func = default_read_func;
    else
	encoder->read_func = read_func;
    encoder->user_val = user_val;

    return encoder;
}

void close_deflate_handler(DeflateHandler encoder)
{
    free(encoder);
}

local void init_deflate(DeflateHandler encoder)
{
    if(encoder->eofile)
	return;
    encoder->bi_buf = 0;
    encoder->bi_valid = 0;
    ct_init(encoder);
    lm_init(encoder);

    encoder->qhead = NULL;
    encoder->outcnt = 0;

    if(encoder->compr_level <= 3)
    {
	encoder->prev_length = MIN_MATCH - 1;
	encoder->match_length = 0;
    }
    else
    {
	encoder->match_length = MIN_MATCH - 1;
	encoder->match_available = 0;
    }

    encoder->complete = 0;
}

/* ===========================================================================
 * Same as above, but achieves better compression. We use a lazy
 * evaluation for matches: a match is finally adopted only if there is
 * no better match at the next window position.
 */
long zip_deflate(DeflateHandler encoder, char *buff, long buff_size)
{
    long n;

    if(!encoder->initflag)
    {
	init_deflate(encoder);
	encoder->initflag = 1;
	if(encoder->lookahead == 0) { /* empty */
	    encoder->complete = 1;
	    return 0;
	}
    }

    if((n = qcopy(encoder, buff, buff_size)) == buff_size)
	return buff_size;

    if(encoder->complete)
	return n;

    if(encoder->compr_level <= 3) /* optimized for speed */
	deflate_fast(encoder);
    else
	deflate_better(encoder);
    if(encoder->lookahead == 0)
    {
	if(encoder->match_available)
	    ct_tally(encoder, 0, encoder->window[encoder->strstart - 1]);
	flush_block(encoder, 1);
	encoder->complete = 1;
    }
    return n + qcopy(encoder, buff + n, buff_size - n);
}

local long qcopy(DeflateHandler encoder, char *buff, long buff_size)
{
  struct deflate_buff_queue *q;
    long n, i;

    n = 0;
    q = encoder->qhead;
    while(q != NULL && n < buff_size)
    {
	i = buff_size - n;
	if(i > q->len)
	    i = q->len;
	memcpy(buff + n, q->ptr, i);
	q->ptr += i;
	q->len -= i;
	n += i;

	if(q->len == 0)
	{
	    struct deflate_buff_queue *p;
	    p = q;
	    q = q->next;
	    reuse_queue(p);
	}
    }
    encoder->qhead = q;
    if(n == buff_size)
      return n;

    if(encoder->outoff < encoder->outcnt)
    {
	i = buff_size - n;
	if(i > encoder->outcnt - encoder->outoff)
	    i = encoder->outcnt - encoder->outoff;
	memcpy(buff + n, encoder->outbuf + encoder->outoff, i);
	encoder->outoff += i;
	n += i;
	if(encoder->outcnt == encoder->outoff)
	    encoder->outcnt = encoder->outoff = 0;
    }
    return n;
}


/* ===========================================================================
 * Allocate the match buffer, initialize the various tables and save the
 * location of the internal file attribute (ascii/binary) and method
 * (DEFLATE/STORE).
 */