javascript deflate

/*
 * http://www.onicos.com/staff/iz/amuse/javascript/expert/deflate.txt
 */

/* Interface:
 * data = zip_deflate(src);
 */

/* constant parameters */
var zip_WSIZE = 32768;      // Sliding Window size
var zip_STORED_BLOCK = 0;
var zip_STATIC_TREES = 1;
var zip_DYN_TREES    = 2;

/* for deflate */
var zip_DEFAULT_LEVEL = 6;
var zip_FULL_SEARCH = true;
var zip_INBUFSIZ = 32768;   // Input buffer size
var zip_INBUF_EXTRA = 64;   // Extra buffer
var zip_OUTBUFSIZ = 1024 * 8;
var zip_window_size = 2 * zip_WSIZE;
var zip_MIN_MATCH = 3;
var zip_MAX_MATCH = 258;
var zip_BITS = 16;
// for SMALL_MEM
var zip_LIT_BUFSIZE = 0x2000;
var zip_HASH_BITS = 13;
// for MEDIUM_MEM
// var zip_LIT_BUFSIZE = 0x4000;
// var zip_HASH_BITS = 14;
// for BIG_MEM
// var zip_LIT_BUFSIZE = 0x8000;
// var zip_HASH_BITS = 15;
if(zip_LIT_BUFSIZE > zip_INBUFSIZ)
    alert("error: zip_INBUFSIZ is too small");
if((zip_WSIZE<<1) > (1<<zip_BITS))
    alert("error: zip_WSIZE is too large");
if(zip_HASH_BITS > zip_BITS-1)
    alert("error: zip_HASH_BITS is too large");
if(zip_HASH_BITS < 8 || zip_MAX_MATCH != 258)
    alert("error: Code too clever");
var zip_DIST_BUFSIZE = zip_LIT_BUFSIZE;
var zip_HASH_SIZE = 1 << zip_HASH_BITS;
var zip_HASH_MASK = zip_HASH_SIZE - 1;
var zip_WMASK = zip_WSIZE - 1;
var zip_NIL = 0; // Tail of hash chains
var zip_TOO_FAR = 4096;
var zip_MIN_LOOKAHEAD = zip_MAX_MATCH + zip_MIN_MATCH + 1;
var zip_MAX_DIST = zip_WSIZE - zip_MIN_LOOKAHEAD;
var zip_SMALLEST = 1;
var zip_MAX_BITS = 15;
var zip_MAX_BL_BITS = 7;
var zip_LENGTH_CODES = 29;
var zip_LITERALS =256;
var zip_END_BLOCK = 256;
var zip_L_CODES = zip_LITERALS + 1 + zip_LENGTH_CODES;
var zip_D_CODES = 30;
var zip_BL_CODES = 19;
var zip_REP_3_6 = 16;
var zip_REPZ_3_10 = 17;
var zip_REPZ_11_138 = 18;
var zip_HEAP_SIZE = 2 * zip_L_CODES + 1;
var zip_H_SHIFT = parseInt((zip_HASH_BITS + zip_MIN_MATCH - 1) /
               zip_MIN_MATCH);

/* variables */
var zip_free_queue;
var zip_qhead, zip_qtail;
var zip_initflag;
var zip_outbuf = null;
var zip_outcnt, zip_outoff;
var zip_complete;
var zip_window;
var zip_d_buf;
var zip_l_buf;
var zip_prev;
var zip_bi_buf;
var zip_bi_valid;
var zip_block_start;
var zip_ins_h;
var zip_hash_head;
var zip_prev_match;
var zip_match_available;
var zip_match_length;
var zip_prev_length;
var zip_strstart;
var zip_match_start;
var zip_eofile;
var zip_lookahead;
var zip_max_chain_length;
var zip_max_lazy_match;
var zip_compr_level;
var zip_good_match;
var zip_nice_match;
var zip_dyn_ltree;
var zip_dyn_dtree;
var zip_static_ltree;
var zip_static_dtree;
var zip_bl_tree;
var zip_l_desc;
var zip_d_desc;
var zip_bl_desc;
var zip_bl_count;
var zip_heap;
var zip_heap_len;
var zip_heap_max;
var zip_depth;
var zip_length_code;
var zip_dist_code;
var zip_base_length;
var zip_base_dist;
var zip_flag_buf;
var zip_last_lit;
var zip_last_dist;
var zip_last_flags;
var zip_flags;
var zip_flag_bit;
var zip_opt_len;
var zip_static_len;
var zip_deflate_data;
var zip_deflate_pos;

/* constant tables */
var zip_extra_lbits = new Array(
    0,0,0,0,0,0,0,0,1,1,1,1,2,2,2,2,3,3,3,3,4,4,4,4,5,5,5,5,0);
var zip_extra_dbits = new Array(
    0,0,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13);
var zip_extra_blbits = new Array(
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7);
var zip_bl_order = new Array(
    16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15);
var zip_configuration_table = new Array(
    new zip_DeflateConfiguration(0,    0,   0,    0),
    new zip_DeflateConfiguration(4,    4,   8,    4),
    new zip_DeflateConfiguration(4,    5,  16,    8),
    new zip_DeflateConfiguration(4,    6,  32,   32),
    new zip_DeflateConfiguration(4,    4,  16,   16),
    new zip_DeflateConfiguration(8,   16,  32,   32),
    new zip_DeflateConfiguration(8,   16, 128,  128),
    new zip_DeflateConfiguration(8,   32, 128,  256),
    new zip_DeflateConfiguration(32, 128, 258, 1024),
    new zip_DeflateConfiguration(32, 258, 258, 4096));

/* objects (deflate) */

function zip_DeflateCT() {
    this.fc = 0; // frequency count or bit string
    this.dl = 0; // father node in Huffman tree or length of bit string
}

function zip_DeflateTreeDesc() {
    this.dyn_tree = null;   // the dynamic tree
    this.static_tree = null;    // corresponding static tree or NULL
    this.extra_bits = null; // extra bits for each code or NULL
    this.extra_base = 0;    // base index for extra_bits
    this.elems = 0;     // max number of elements in the tree
    this.max_length = 0;    // max bit length for the codes
    this.max_code = 0;      // largest code with non zero frequency
}

/* Values for max_lazy_match, good_match and max_chain_length, depending on
 * the desired pack level (0..9). The values given below have been tuned to
 * exclude worst case performance for pathological files. Better values may be
 * found for specific files.
 */
function zip_DeflateConfiguration(a, b, c, d) {
    this.good_length = a; // reduce lazy search above this match length
    this.max_lazy = b;    // do not perform lazy search above this match length
    this.nice_length = c; // quit search above this match length
    this.max_chain = d;
}

function zip_DeflateBuffer() {
    this.next = null;
    this.len = 0;
    this.ptr = new Array(zip_OUTBUFSIZ);
    this.off = 0;
}

/* routines (deflate) */

function zip_deflate_start(level) {
    var i;

    if(!level)
    level = zip_DEFAULT_LEVEL;
    else if(level < 1)
    level = 1;
    else if(level > 9)
    level = 9;

    zip_compr_level = level;
    zip_initflag = false;
    zip_eofile = false;
    if(zip_outbuf != null)
    return;

    zip_free_queue = zip_qhead = zip_qtail = null;
    zip_outbuf = new Array(zip_OUTBUFSIZ);
    zip_window = new Array(zip_window_size);
    zip_d_buf = new Array(zip_DIST_BUFSIZE);
    zip_l_buf = new Array(zip_INBUFSIZ + zip_INBUF_EXTRA);
    zip_prev = new Array(1 << zip_BITS);
    zip_dyn_ltree = new Array(zip_HEAP_SIZE);
    for(i = 0; i < zip_HEAP_SIZE; i++)
    zip_dyn_ltree[i] = new zip_DeflateCT();
    zip_dyn_dtree = new Array(2*zip_D_CODES+1);
    for(i = 0; i < 2*zip_D_CODES+1; i++)
    zip_dyn_dtree[i] = new zip_DeflateCT();
    zip_static_ltree = new Array(zip_L_CODES+2);
    for(i = 0; i < zip_L_CODES+2; i++)
    zip_static_ltree[i] = new zip_DeflateCT();
    zip_static_dtree = new Array(zip_D_CODES);
    for(i = 0; i < zip_D_CODES; i++)
    zip_static_dtree[i] = new zip_DeflateCT();
    zip_bl_tree = new Array(2*zip_BL_CODES+1);
    for(i = 0; i < 2*zip_BL_CODES+1; i++)
    zip_bl_tree[i] = new zip_DeflateCT();
    zip_l_desc = new zip_DeflateTreeDesc();
    zip_d_desc = new zip_DeflateTreeDesc();
    zip_bl_desc = new zip_DeflateTreeDesc();
    zip_bl_count = new Array(zip_MAX_BITS+1);
    zip_heap = new Array(2*zip_L_CODES+1);
    zip_depth = new Array(2*zip_L_CODES+1);
    zip_length_code = new Array(zip_MAX_MATCH-zip_MIN_MATCH+1);
    zip_dist_code = new Array(512);
    zip_base_length = new Array(zip_LENGTH_CODES);
    zip_base_dist = new Array(zip_D_CODES);
    zip_flag_buf = new Array(parseInt(zip_LIT_BUFSIZE / 8));
}

function zip_deflate_end() {
    zip_free_queue = zip_qhead = zip_qtail = null;
    zip_outbuf = null;
    zip_window = null;
    zip_d_buf = null;
    zip_l_buf = null;
    zip_prev = null;
    zip_dyn_ltree = null;
    zip_dyn_dtree = null;
    zip_static_ltree = null;
    zip_static_dtree = null;
    zip_bl_tree = null;
    zip_l_desc = null;
    zip_d_desc = null;
    zip_bl_desc = null;
    zip_bl_count = null;
    zip_heap = null;
    zip_depth = null;
    zip_length_code = null;
    zip_dist_code = null;
    zip_base_length = null;
    zip_base_dist = null;
    zip_flag_buf = null;
}

function zip_reuse_queue(p) {
    p.next = zip_free_queue;
    zip_free_queue = p;
}

function zip_new_queue() {
    var p;

    if(zip_free_queue != null)
    {
    p = zip_free_queue;
    zip_free_queue = zip_free_queue.next;
    }
    else
    p = new zip_DeflateBuffer();
    p.next = null;
    p.len = p.off = 0;

    return p;
}

function zip_head1(i) {
    return zip_prev[zip_WSIZE + i];
}

function zip_head2(i, val) {
    return zip_prev[zip_WSIZE + i] = val;
}

/* put_byte is used for the compressed output, put_ubyte for the
 * uncompressed output. However unlzw() uses window for its
 * suffix table instead of its output buffer, so it does not use put_ubyte
 * (to be cleaned up).
 */
function zip_put_byte(c) {
    zip_outbuf[zip_outoff + zip_outcnt++] = c;
    if(zip_outoff + zip_outcnt == zip_OUTBUFSIZ)
    zip_qoutbuf();
}

/* Output a 16 bit value, lsb first */
function zip_put_short(w) {
    w &= 0xffff;
    if(zip_outoff + zip_outcnt < zip_OUTBUFSIZ - 2) {
    zip_outbuf[zip_outoff + zip_outcnt++] = (w & 0xff);
    zip_outbuf[zip_outoff + zip_outcnt++] = (w >>> 8);
    } else {
    zip_put_byte(w & 0xff);
    zip_put_byte(w >>> 8);
    }
}

/* ==========================================================================
 * Insert string s in the dictionary and set match_head to the previous head
 * of the hash chain (the most recent string with same hash key). Return
 * the previous length of the hash chain.
 * IN  assertion: all calls to to INSERT_STRING are made with consecutive
 *    input characters and the first MIN_MATCH bytes of s are valid
 *    (except for the last MIN_MATCH-1 bytes of the input file).
 */
function zip_INSERT_STRING() {
    zip_ins_h = ((zip_ins_h << zip_H_SHIFT)
         ^ (zip_window[zip_strstart + zip_MIN_MATCH - 1] & 0xff))
    & zip_HASH_MASK;
    zip_hash_head = zip_head1(zip_ins_h);
    zip_prev[zip_strstart & zip_WMASK] = zip_hash_head;
    zip_head2(zip_ins_h, zip_strstart);
}

/* Send a code of the given tree. c and tree must not have side effects */
function zip_SEND_CODE(c, tree) {
    zip_send_bits(tree[c].fc, tree[c].dl);
}

/* Mapping from a distance to a distance code. dist is the distance - 1 and
 * must not have side effects. dist_code[256] and dist_code[257] are never
 * used.
 */
function zip_D_CODE(dist) {
    return (dist < 256 ? zip_dist_code[dist]
        : zip_dist_code[256 + (dist>>7)]) & 0xff;
}

/* ==========================================================================
 * Compares to subtrees, using the tree depth as tie breaker when
 * the subtrees have equal frequency. This minimizes the worst case length.
 */
function zip_SMALLER(tree, n, m) {
    return tree[n].fc < tree[m].fc ||
      (tree[n].fc == tree[m].fc && zip_depth[n] <= zip_depth[m]);
}

/* ==========================================================================
 * read string data
 */
function zip_read_buff(buff, offset, n) {
    var i;
    for(i = 0; i < n && zip_deflate_pos < zip_deflate_data.length; i++)
    buff[offset + i] =
        zip_deflate_data.charCodeAt(zip_deflate_pos++) & 0xff;
    return i;
}

/* ==========================================================================
 * Initialize the "longest match" routines for a new file
 */
function zip_lm_init() {
    var j;

    /* Initialize the hash table. */
    for(j = 0; j < zip_HASH_SIZE; j++)
//  zip_head2(j, zip_NIL);
    zip_prev[zip_WSIZE + j] = 0;
    /* prev will be initialized on the fly */

    /* Set the default configuration parameters:
     */
    zip_max_lazy_match = zip_configuration_table[zip_compr_level].max_lazy;
    zip_good_match     = zip_configuration_table[zip_compr_level].good_length;
    if(!zip_FULL_SEARCH)
    zip_nice_match = zip_configuration_table[zip_compr_level].nice_length;
    zip_max_chain_length = zip_configuration_table[zip_compr_level].max_chain;

    zip_strstart = 0;
    zip_block_start = 0;

    zip_lookahead = zip_read_buff(zip_window, 0, 2 * zip_WSIZE);
    if(zip_lookahead <= 0) {
    zip_eofile = true;
    zip_lookahead = 0;
    return;
    }
    zip_eofile = false;
    /* Make sure that we always have enough lookahead. This is important
     * if input comes from a device such as a tty.
     */
    while(zip_lookahead < zip_MIN_LOOKAHEAD && !zip_eofile)
    zip_fill_window();

    /* If lookahead < MIN_MATCH, ins_h is garbage, but this is
     * not important since only literal bytes will be emitted.
     */
    zip_ins_h = 0;
    for(j = 0; j < zip_MIN_MATCH - 1; j++) {
//      UPDATE_HASH(ins_h, window[j]);
    zip_ins_h = ((zip_ins_h << zip_H_SHIFT) ^ (zip_window[j] & 0xff)) & zip_HASH_MASK;
    }
}

/* ==========================================================================
 * Set match_start to the longest match starting at the given string and
 * return its length. Matches shorter or equal to prev_length are discarded,
 * in which case the result is equal to prev_length and match_start is
 * garbage.
 * IN assertions: cur_match is the head of the hash chain for the current
 *   string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
 */
function zip_longest_match(cur_match) {
    var chain_length = zip_max_chain_length; // max hash chain length
    var scanp = zip_strstart; // current string
    var matchp;     // matched string
    var len;        // length of current match
    var best_len = zip_prev_length; // best match length so far

    /* Stop when cur_match becomes <= limit. To simplify the code,
     * we prevent matches with the string of window index 0.
     */
    var limit = (zip_strstart > zip_MAX_DIST ? zip_strstart - zip_MAX_DIST : zip_NIL);

    var strendp = zip_strstart + zip_MAX_MATCH;
    var scan_end1 = zip_window[scanp + best_len - 1];
    var scan_end  = zip_window[scanp + best_len];

    /* Do not waste too much time if we already have a good match: */
    if(zip_prev_length >= zip_good_match)
    chain_length >>= 2;

//  Assert(encoder->strstart <= window_size-MIN_LOOKAHEAD, "insufficient lookahead");

    do {
//    Assert(cur_match < encoder->strstart, "no future");
    matchp = cur_match;

    /* Skip to next match if the match length cannot increase
        * or if the match length is less than 2:
    */
    if(zip_window[matchp + best_len]    != scan_end  ||
       zip_window[matchp + best_len - 1]    != scan_end1 ||
       zip_window[matchp]           != zip_window[scanp] ||
       zip_window[++matchp]         != zip_window[scanp + 1]) {
        continue;
    }

    /* The check at best_len-1 can be removed because it will be made
         * again later. (This heuristic is not always a win.)
         * It is not necessary to compare scan[2] and match[2] since they
         * are always equal when the other bytes match, given that
         * the hash keys are equal and that HASH_BITS >= 8.
         */
    scanp += 2;
    matchp++;

    /* We check for insufficient lookahead only every 8th comparison;
         * the 256th check will be made at strstart+258.
         */
    do {
    } while(zip_window[++scanp] == zip_window[++matchp] &&
        zip_window[++scanp] == zip_window[++matchp] &&
        zip_window[++scanp] == zip_window[++matchp] &&
        zip_window[++scanp] == zip_window[++matchp] &&
        zip_window[++scanp] == zip_window[++matchp] &&
        zip_window[++scanp] == zip_window[++matchp] &&
        zip_window[++scanp] == zip_window[++matchp] &&
        zip_window[++scanp] == zip_window[++matchp] &&
        scanp < strendp);

      len = zip_MAX_MATCH - (strendp - scanp);
      scanp = strendp - zip_MAX_MATCH;

      if(len > best_len) {
      zip_match_start = cur_match;
      best_len = len;
      if(zip_FULL_SEARCH) {
          if(len >= zip_MAX_MATCH) break;
      } else {
          if(len >= zip_nice_match) break;
      }

      scan_end1  = zip_window[scanp + best_len-1];
      scan_end   = zip_window[scanp + best_len];
      }
    } while((cur_match = zip_prev[cur_match & zip_WMASK]) > limit
        && --chain_length != 0);

    return best_len;
}

/* ==========================================================================
 * Fill the window when the lookahead becomes insufficient.
 * Updates strstart and lookahead, and sets eofile if end of input file.
 * IN assertion: lookahead < MIN_LOOKAHEAD && strstart + lookahead > 0
 * OUT assertions: at least one byte has been read, or eofile is set;
 *    file reads are performed for at least two bytes (required for the
 *    translate_eol option).
 */
function zip_fill_window() {
    var n, m;

    // Amount of free space at the end of the window.
    var more = zip_window_size - zip_lookahead - zip_strstart;

    /* If the window is almost full and there is insufficient lookahead,
     * move the upper half to the lower one to make room in the upper half.
     */
    if(more == -1) {
    /* Very unlikely, but possible on 16 bit machine if strstart == 0
         * and lookahead == 1 (input done one byte at time)
         */
    more--;
    } else if(zip_strstart >= zip_WSIZE + zip_MAX_DIST) {
    /* By the IN assertion, the window is not empty so we can't confuse
         * more == 0 with more == 64K on a 16 bit machine.
         */
//  Assert(window_size == (ulg)2*WSIZE, "no sliding with BIG_MEM");

//  System.arraycopy(window, WSIZE, window, 0, WSIZE);
    for(n = 0; n < zip_WSIZE; n++)
        zip_window[n] = zip_window[n + zip_WSIZE];

    zip_match_start -= zip_WSIZE;
    zip_strstart    -= zip_WSIZE; /* we now have strstart >= MAX_DIST: */
    zip_block_start -= zip_WSIZE;

    for(n = 0; n < zip_HASH_SIZE; n++) {
        m = zip_head1(n);
        zip_head2(n, m >= zip_WSIZE ? m - zip_WSIZE : zip_NIL);
    }
    for(n = 0; n < zip_WSIZE; n++) {
        /* If n is not on any hash chain, prev[n] is garbage but
         * its value will never be used.
         */
        m = zip_prev[n];
        zip_prev[n] = (m >= zip_WSIZE ? m - zip_WSIZE : zip_NIL);
    }
    more += zip_WSIZE;
    }
    // At this point, more >= 2
    if(!zip_eofile) {
    n = zip_read_buff(zip_window, zip_strstart + zip_lookahead, more);
    if(n <= 0)
        zip_eofile = true;
    else
        zip_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.
 */
function zip_deflate_fast() {
    while(zip_lookahead != 0 && zip_qhead == null) {
    var 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:
     */
    zip_INSERT_STRING();

    /* Find the longest match, discarding those <= prev_length.
     * At this point we have always match_length < MIN_MATCH
     */
    if(zip_hash_head != zip_NIL &&
       zip_strstart - zip_hash_head <= zip_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).
         */
        zip_match_length = zip_longest_match(zip_hash_head);
        /* longest_match() sets match_start */
        if(zip_match_length > zip_lookahead)
        zip_match_length = zip_lookahead;
    }
    if(zip_match_length >= zip_MIN_MATCH) {
//      check_match(strstart, match_start, match_length);

        flush = zip_ct_tally(zip_strstart - zip_match_start,
                 zip_match_length - zip_MIN_MATCH);
        zip_lookahead -= zip_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(zip_match_length <= zip_max_lazy_match) {
        zip_match_length--; // string at strstart already in hash table
        do {
            zip_strstart++;
            zip_INSERT_STRING();
            /* 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(--zip_match_length != 0);
        zip_strstart++;
        } else {
        zip_strstart += zip_match_length;
        zip_match_length = 0;
        zip_ins_h = zip_window[zip_strstart] & 0xff;
//      UPDATE_HASH(ins_h, window[strstart + 1]);
        zip_ins_h = ((zip_ins_h<<zip_H_SHIFT) ^ (zip_window[zip_strstart + 1] & 0xff)) & zip_HASH_MASK;

//#if MIN_MATCH != 3
//      Call UPDATE_HASH() MIN_MATCH-3 more times
//#endif

        }
    } else {
        /* No match, output a literal byte */
        flush = zip_ct_tally(0, zip_window[zip_strstart] & 0xff);
        zip_lookahead--;
        zip_strstart++;
    }
    if(flush) {
        zip_flush_block(0);
        zip_block_start = zip_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(zip_lookahead < zip_MIN_LOOKAHEAD && !zip_eofile)
        zip_fill_window();
    }
}

function zip_deflate_better() {
    /* Process the input block. */
    while(zip_lookahead != 0 && zip_qhead == null) {
    /* Insert the string window[strstart .. strstart+2] in the
     * dictionary, and set hash_head to the head of the hash chain:
     */
    zip_INSERT_STRING();

    /* Find the longest match, discarding those <= prev_length.
     */
    zip_prev_length = zip_match_length;
    zip_prev_match = zip_match_start;
    zip_match_length = zip_MIN_MATCH - 1;

    if(zip_hash_head != zip_NIL &&
       zip_prev_length < zip_max_lazy_match &&
       zip_strstart - zip_hash_head <= zip_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).
         */
        zip_match_length = zip_longest_match(zip_hash_head);
        /* longest_match() sets match_start */
        if(zip_match_length > zip_lookahead)
        zip_match_length = zip_lookahead;

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

//      check_match(strstart - 1, prev_match, prev_length);
        flush = zip_ct_tally(zip_strstart - 1 - zip_prev_match,
                 zip_prev_length - zip_MIN_MATCH);

        /* Insert in hash table all strings up to the end of the match.
         * strstart-1 and strstart are already inserted.
         */
        zip_lookahead -= zip_prev_length - 1;
        zip_prev_length -= 2;
        do {
        zip_strstart++;
        zip_INSERT_STRING();
        /* 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(--zip_prev_length != 0);
        zip_match_available = 0;
        zip_match_length = zip_MIN_MATCH - 1;
        zip_strstart++;
        if(flush) {
        zip_flush_block(0);
        zip_block_start = zip_strstart;
        }
    } else if(zip_match_available != 0) {
        /* 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.
         */
        if(zip_ct_tally(0, zip_window[zip_strstart - 1] & 0xff)) {
        zip_flush_block(0);
        zip_block_start = zip_strstart;
        }
        zip_strstart++;
        zip_lookahead--;
    } else {
        /* There is no previous match to compare with, wait for
         * the next step to decide.
         */
        zip_match_available = 1;
        zip_strstart++;
        zip_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(zip_lookahead < zip_MIN_LOOKAHEAD && !zip_eofile)
        zip_fill_window();
    }
}

function zip_init_deflate() {
    if(zip_eofile)
    return;
    zip_bi_buf = 0;
    zip_bi_valid = 0;
    zip_ct_init();
    zip_lm_init();

    zip_qhead = null;
    zip_outcnt = 0;
    zip_outoff = 0;

    if(zip_compr_level <= 3)
    {
    zip_prev_length = zip_MIN_MATCH - 1;
    zip_match_length = 0;
    }
    else
    {
    zip_match_length = zip_MIN_MATCH - 1;
    zip_match_available = 0;
    }

    zip_complete = false;
}

/* ==========================================================================
 * 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.
 */
function zip_deflate_internal(buff, off, buff_size) {
    var n;

    if(!zip_initflag)
    {
    zip_init_deflate();
    zip_initflag = true;
    if(zip_lookahead == 0) { // empty
        zip_complete = true;
        return 0;
    }
    }

    if((n = zip_qcopy(buff, off, buff_size)) == buff_size)
    return buff_size;

    if(zip_complete)
    return n;

    if(zip_compr_level <= 3) // optimized for speed
    zip_deflate_fast();
    else
    zip_deflate_better();
    if(zip_lookahead == 0) {
    if(zip_match_available != 0)
        zip_ct_tally(0, zip_window[zip_strstart - 1] & 0xff);
    zip_flush_block(1);
    zip_complete = true;
    }
    return n + zip_qcopy(buff, n + off, buff_size - n);
}

function zip_qcopy(buff, off, buff_size) {
    var n, i, j;

    n = 0;
    while(zip_qhead != null && n < buff_size)
    {
    i = buff_size - n;
    if(i > zip_qhead.len)
        i = zip_qhead.len;
//      System.arraycopy(qhead.ptr, qhead.off, buff, off + n, i);
    for(j = 0; j < i; j++)
        buff[off + n + j] = zip_qhead.ptr[zip_qhead.off + j];

    zip_qhead.off += i;
    zip_qhead.len -= i;
    n += i;
    if(zip_qhead.len == 0) {
        var p;
        p = zip_qhead;
        zip_qhead = zip_qhead.next;
        zip_reuse_queue(p);
    }
    }

    if(n == buff_size)
    return n;

    if(zip_outoff < zip_outcnt) {
    i = buff_size - n;
    if(i > zip_outcnt - zip_outoff)
        i = zip_outcnt - zip_outoff;
    // System.arraycopy(outbuf, outoff, buff, off + n, i);
    for(j = 0; j < i; j++)
        buff[off + n + j] = zip_outbuf[zip_outoff + j];
    zip_outoff += i;
    n += i;
    if(zip_outcnt == zip_outoff)
        zip_outcnt = zip_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).
 */
function zip_ct_init() {
    var n;  // iterates over tree elements
    var bits;   // bit counter
    var length; // length value
    var code;   // code value
    var dist;   // distance index

    if(zip_static_dtree[0].dl != 0) return; // ct_init already called

    zip_l_desc.dyn_tree     = zip_dyn_ltree;
    zip_l_desc.static_tree  = zip_static_ltree;
    zip_l_desc.extra_bits   = zip_extra_lbits;
    zip_l_desc.extra_base   = zip_LITERALS + 1;
    zip_l_desc.elems        = zip_L_CODES;
    zip_l_desc.max_length   = zip_MAX_BITS;
    zip_l_desc.max_code     = 0;

    zip_d_desc.dyn_tree     = zip_dyn_dtree;
    zip_d_desc.static_tree  = zip_static_dtree;
    zip_d_desc.extra_bits   = zip_extra_dbits;
    zip_d_desc.extra_base   = 0;
    zip_d_desc.elems        = zip_D_CODES;
    zip_d_desc.max_length   = zip_MAX_BITS;
    zip_d_desc.max_code     = 0;

    zip_bl_desc.dyn_tree    = zip_bl_tree;
    zip_bl_desc.static_tree = null;
    zip_bl_desc.extra_bits  = zip_extra_blbits;
    zip_bl_desc.extra_base  = 0;
    zip_bl_desc.elems       = zip_BL_CODES;
    zip_bl_desc.max_length  = zip_MAX_BL_BITS;
    zip_bl_desc.max_code    = 0;

    // Initialize the mapping length (0..255) -> length code (0..28)
    length = 0;
    for(code = 0; code < zip_LENGTH_CODES-1; code++) {
    zip_base_length[code] = length;
    for(n = 0; n < (1<<zip_extra_lbits[code]); n++)
        zip_length_code[length++] = code;
    }
    // Assert (length == 256, "ct_init: length != 256");

    /* Note that the length 255 (match length 258) can be represented
     * in two different ways: code 284 + 5 bits or code 285, so we
     * overwrite length_code[255] to use the best encoding:
     */
    zip_length_code[length-1] = code;

    /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
    dist = 0;
    for(code = 0 ; code < 16; code++) {
    zip_base_dist[code] = dist;
    for(n = 0; n < (1<<zip_extra_dbits[code]); n++) {
        zip_dist_code[dist++] = code;
    }
    }
    // Assert (dist == 256, "ct_init: dist != 256");
    dist >>= 7; // from now on, all distances are divided by 128
    for( ; code < zip_D_CODES; code++) {
    zip_base_dist[code] = dist << 7;
    for(n = 0; n < (1<<(zip_extra_dbits[code]-7)); n++)
        zip_dist_code[256 + dist++] = code;
    }
    // Assert (dist == 256, "ct_init: 256+dist != 512");

    // Construct the codes of the static literal tree
    for(bits = 0; bits <= zip_MAX_BITS; bits++)
    zip_bl_count[bits] = 0;
    n = 0;
    while(n <= 143) { zip_static_ltree[n++].dl = 8; zip_bl_count[8]++; }
    while(n <= 255) { zip_static_ltree[n++].dl = 9; zip_bl_count[9]++; }
    while(n <= 279) { zip_static_ltree[n++].dl = 7; zip_bl_count[7]++; }
    while(n <= 287) { zip_static_ltree[n++].dl = 8; zip_bl_count[8]++; }
    /* Codes 286 and 287 do not exist, but we must include them in the
     * tree construction to get a canonical Huffman tree (longest code
     * all ones)
     */
    zip_gen_codes(zip_static_ltree, zip_L_CODES + 1);

    /* The static distance tree is trivial: */
    for(n = 0; n < zip_D_CODES; n++) {
    zip_static_dtree[n].dl = 5;
    zip_static_dtree[n].fc = zip_bi_reverse(n, 5);
    }

    // Initialize the first block of the first file:
    zip_init_block();
}

/* ==========================================================================
 * Initialize a new block.
 */
function zip_init_block() {
    var n; // iterates over tree elements

    // Initialize the trees.
    for(n = 0; n < zip_L_CODES;  n++) zip_dyn_ltree[n].fc = 0;
    for(n = 0; n < zip_D_CODES;  n++) zip_dyn_dtree[n].fc = 0;
    for(n = 0; n < zip_BL_CODES; n++) zip_bl_tree[n].fc = 0;

    zip_dyn_ltree[zip_END_BLOCK].fc = 1;
    zip_opt_len = zip_static_len = 0;
    zip_last_lit = zip_last_dist = zip_last_flags = 0;
    zip_flags = 0;
    zip_flag_bit = 1;
}

/* ==========================================================================
 * Restore the heap property by moving down the tree starting at node k,
 * exchanging a node with the smallest of its two sons if necessary, stopping
 * when the heap property is re-established (each father smaller than its
 * two sons).
 */
function zip_pqdownheap(
    tree,   // the tree to restore
    k) {    // node to move down
    var v = zip_heap[k];
    var j = k << 1; // left son of k

    while(j <= zip_heap_len) {
    // Set j to the smallest of the two sons:
    if(j < zip_heap_len &&
       zip_SMALLER(tree, zip_heap[j + 1], zip_heap[j]))
        j++;

    // Exit if v is smaller than both sons
    if(zip_SMALLER(tree, v, zip_heap[j]))
        break;

    // Exchange v with the smallest son
    zip_heap[k] = zip_heap[j];
    k = j;

    // And continue down the tree, setting j to the left son of k
    j <<= 1;
    }
    zip_heap[k] = v;
}

/* ==========================================================================
 * Compute the optimal bit lengths for a tree and update the total bit length
 * for the current block.
 * IN assertion: the fields freq and dad are set, heap[heap_max] and
 *    above are the tree nodes sorted by increasing frequency.
 * OUT assertions: the field len is set to the optimal bit length, the
 *     array bl_count contains the frequencies for each bit length.
 *     The length opt_len is updated; static_len is also updated if stree is
 *     not null.
 */
function zip_gen_bitlen(desc) { // the tree descriptor
    var tree        = desc.dyn_tree;
    var extra       = desc.extra_bits;
    var base        = desc.extra_base;
    var max_code    = desc.max_code;
    var max_length  = desc.max_length;
    var stree       = desc.static_tree;
    var h;      // heap index
    var n, m;       // iterate over the tree elements
    var bits;       // bit length
    var xbits;      // extra bits
    var f;      // frequency
    var overflow = 0;   // number of elements with bit length too large

    for(bits = 0; bits <= zip_MAX_BITS; bits++)
    zip_bl_count[bits] = 0;

    /* In a first pass, compute the optimal bit lengths (which may
     * overflow in the case of the bit length tree).
     */
    tree[zip_heap[zip_heap_max]].dl = 0; // root of the heap

    for(h = zip_heap_max + 1; h < zip_HEAP_SIZE; h++) {
    n = zip_heap[h];
    bits = tree[tree[n].dl].dl + 1;
    if(bits > max_length) {
        bits = max_length;
        overflow++;
    }
    tree[n].dl = bits;
    // We overwrite tree[n].dl which is no longer needed

    if(n > max_code)
        continue; // not a leaf node

    zip_bl_count[bits]++;
    xbits = 0;
    if(n >= base)
        xbits = extra[n - base];
    f = tree[n].fc;
    zip_opt_len += f * (bits + xbits);
    if(stree != null)
        zip_static_len += f * (stree[n].dl + xbits);
    }
    if(overflow == 0)
    return;

    // This happens for example on obj2 and pic of the Calgary corpus

    // Find the first bit length which could increase:
    do {
    bits = max_length - 1;
    while(zip_bl_count[bits] == 0)
        bits--;
    zip_bl_count[bits]--;       // move one leaf down the tree
    zip_bl_count[bits + 1] += 2;    // move one overflow item as its brother
    zip_bl_count[max_length]--;
    /* The brother of the overflow item also moves one step up,
     * but this does not affect bl_count[max_length]
     */
    overflow -= 2;
    } while(overflow > 0);

    /* Now recompute all bit lengths, scanning in increasing frequency.
     * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
     * lengths instead of fixing only the wrong ones. This idea is taken
     * from 'ar' written by Haruhiko Okumura.)
     */
    for(bits = max_length; bits != 0; bits--) {
    n = zip_bl_count[bits];
    while(n != 0) {
        m = zip_heap[--h];
        if(m > max_code)
        continue;
        if(tree[m].dl != bits) {
        zip_opt_len += (bits - tree[m].dl) * tree[m].fc;
        tree[m].fc = bits;
        }
        n--;
    }
    }
}

  /* ==========================================================================
   * Generate the codes for a given tree and bit counts (which need not be
   * optimal).
   * IN assertion: the array bl_count contains the bit length statistics for
   * the given tree and the field len is set for all tree elements.
   * OUT assertion: the field code is set for all tree elements of non
   *     zero code length.
   */
function zip_gen_codes(tree,    // the tree to decorate
           max_code) {  // largest code with non zero frequency
    var next_code = new Array(zip_MAX_BITS+1); // next code value for each bit length
    var code = 0;       // running code value
    var bits;           // bit index
    var n;          // code index

    /* The distribution counts are first used to generate the code values
     * without bit reversal.
     */
    for(bits = 1; bits <= zip_MAX_BITS; bits++) {
    code = ((code + zip_bl_count[bits-1]) << 1);
    next_code[bits] = code;
    }

    /* Check that the bit counts in bl_count are consistent. The last code
     * must be all ones.
     */
//    Assert (code + encoder->bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
//      "inconsistent bit counts");
//    Tracev((stderr,"\ngen_codes: max_code %d ", max_code));

    for(n = 0; n <= max_code; n++) {
    var len = tree[n].dl;
    if(len == 0)
        continue;
    // Now reverse the bits
    tree[n].fc = zip_bi_reverse(next_code[len]++, len);

//      Tracec(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
//    n, (isgraph(n) ? n : ' '), len, tree[n].fc, next_code[len]-1));
    }
}

/* ==========================================================================
 * Construct one Huffman tree and assigns the code bit strings and lengths.
 * Update the total bit length for the current block.
 * IN assertion: the field freq is set for all tree elements.
 * OUT assertions: the fields len and code are set to the optimal bit length
 *     and corresponding code. The length opt_len is updated; static_len is
 *     also updated if stree is not null. The field max_code is set.
 */
function zip_build_tree(desc) { // the tree descriptor
    var tree    = desc.dyn_tree;
    var stree   = desc.static_tree;
    var elems   = desc.elems;
    var n, m;       // iterate over heap elements
    var max_code = -1;  // largest code with non zero frequency
    var node = elems;   // next internal node of the tree

    /* Construct the initial heap, with least frequent element in
     * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
     * heap[0] is not used.
     */
    zip_heap_len = 0;
    zip_heap_max = zip_HEAP_SIZE;

    for(n = 0; n < elems; n++) {
    if(tree[n].fc != 0) {
        zip_heap[++zip_heap_len] = max_code = n;
        zip_depth[n] = 0;
    } else
        tree[n].dl = 0;
    }

    /* The pkzip format requires that at least one distance code exists,
     * and that at least one bit should be sent even if there is only one
     * possible code. So to avoid special checks later on we force at least
     * two codes of non zero frequency.
     */
    while(zip_heap_len < 2) {
    var xnew = zip_heap[++zip_heap_len] = (max_code < 2 ? ++max_code : 0);
    tree[xnew].fc = 1;
    zip_depth[xnew] = 0;
    zip_opt_len--;
    if(stree != null)
        zip_static_len -= stree[xnew].dl;
    // new is 0 or 1 so it does not have extra bits
    }
    desc.max_code = max_code;

    /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
     * establish sub-heaps of increasing lengths:
     */
    for(n = zip_heap_len >> 1; n >= 1; n--)
    zip_pqdownheap(tree, n);

    /* Construct the Huffman tree by repeatedly combining the least two
     * frequent nodes.
     */
    do {
    n = zip_heap[zip_SMALLEST];
    zip_heap[zip_SMALLEST] = zip_heap[zip_heap_len--];
    zip_pqdownheap(tree, zip_SMALLEST);

    m = zip_heap[zip_SMALLEST];  // m = node of next least frequency

    // keep the nodes sorted by frequency
    zip_heap[--zip_heap_max] = n;
    zip_heap[--zip_heap_max] = m;

    // Create a new node father of n and m
    tree[node].fc = tree[n].fc + tree[m].fc;
//  depth[node] = (char)(MAX(depth[n], depth[m]) + 1);
    if(zip_depth[n] > zip_depth[m] + 1)
        zip_depth[node] = zip_depth[n];
    else
        zip_depth[node] = zip_depth[m] + 1;
    tree[n].dl = tree[m].dl = node;

    // and insert the new node in the heap
    zip_heap[zip_SMALLEST] = node++;
    zip_pqdownheap(tree, zip_SMALLEST);

    } while(zip_heap_len >= 2);

    zip_heap[--zip_heap_max] = zip_heap[zip_SMALLEST];

    /* At this point, the fields freq and dad are set. We can now
     * generate the bit lengths.
     */
    zip_gen_bitlen(desc);

    // The field len is now set, we can generate the bit codes
    zip_gen_codes(tree, max_code);
}

/* ==========================================================================
 * Scan a literal or distance tree to determine the frequencies of the codes
 * in the bit length tree. Updates opt_len to take into account the repeat
 * counts. (The contribution of the bit length codes will be added later
 * during the construction of bl_tree.)
 */
function zip_scan_tree(tree,// the tree to be scanned
               max_code) {  // and its largest code of non zero frequency
    var n;          // iterates over all tree elements
    var prevlen = -1;       // last emitted length
    var curlen;         // length of current code
    var nextlen = tree[0].dl;   // length of next code
    var count = 0;      // repeat count of the current code
    var max_count = 7;      // max repeat count
    var min_count = 4;      // min repeat count

    if(nextlen == 0) {
    max_count = 138;
    min_count = 3;
    }
    tree[max_code + 1].dl = 0xffff; // guard

    for(n = 0; n <= max_code; n++) {
    curlen = nextlen;
    nextlen = tree[n + 1].dl;
    if(++count < max_count && curlen == nextlen)
        continue;
    else if(count < min_count)
        zip_bl_tree[curlen].fc += count;
    else if(curlen != 0) {
        if(curlen != prevlen)
        zip_bl_tree[curlen].fc++;
        zip_bl_tree[zip_REP_3_6].fc++;
    } else if(count <= 10)
        zip_bl_tree[zip_REPZ_3_10].fc++;
    else
        zip_bl_tree[zip_REPZ_11_138].fc++;
    count = 0; prevlen = curlen;
    if(nextlen == 0) {
        max_count = 138;
        min_count = 3;
    } else if(curlen == nextlen) {
        max_count = 6;
        min_count = 3;
    } else {
        max_count = 7;
        min_count = 4;
    }
    }
}

  /* ==========================================================================
   * Send a literal or distance tree in compressed form, using the codes in
   * bl_tree.
   */
function zip_send_tree(tree, // the tree to be scanned
           max_code) { // and its largest code of non zero frequency
    var n;          // iterates over all tree elements
    var prevlen = -1;       // last emitted length
    var curlen;         // length of current code
    var nextlen = tree[0].dl;   // length of next code
    var count = 0;      // repeat count of the current code
    var max_count = 7;      // max repeat count
    var min_count = 4;      // min repeat count

    /* tree[max_code+1].dl = -1; */  /* guard already set */
    if(nextlen == 0) {
      max_count = 138;
      min_count = 3;
    }

    for(n = 0; n <= max_code; n++) {
    curlen = nextlen;
    nextlen = tree[n+1].dl;
    if(++count < max_count && curlen == nextlen) {
        continue;
    } else if(count < min_count) {
        do { zip_SEND_CODE(curlen, zip_bl_tree); } while(--count != 0);
    } else if(curlen != 0) {
        if(curlen != prevlen) {
        zip_SEND_CODE(curlen, zip_bl_tree);
        count--;
        }
        // Assert(count >= 3 && count <= 6, " 3_6?");
        zip_SEND_CODE(zip_REP_3_6, zip_bl_tree);
        zip_send_bits(count - 3, 2);
    } else if(count <= 10) {
        zip_SEND_CODE(zip_REPZ_3_10, zip_bl_tree);
        zip_send_bits(count-3, 3);
    } else {
        zip_SEND_CODE(zip_REPZ_11_138, zip_bl_tree);
        zip_send_bits(count-11, 7);
    }
    count = 0;
    prevlen = curlen;
    if(nextlen == 0) {
        max_count = 138;
        min_count = 3;
    } else if(curlen == nextlen) {
        max_count = 6;
        min_count = 3;
    } else {
        max_count = 7;
        min_count = 4;
    }
    }
}

/* ==========================================================================
 * Construct the Huffman tree for the bit lengths and return the index in
 * bl_order of the last bit length code to send.
 */
function zip_build_bl_tree() {
    var max_blindex;  // index of last bit length code of non zero freq

    // Determine the bit length frequencies for literal and distance trees
    zip_scan_tree(zip_dyn_ltree, zip_l_desc.max_code);
    zip_scan_tree(zip_dyn_dtree, zip_d_desc.max_code);

    // Build the bit length tree:
    zip_build_tree(zip_bl_desc);
    /* opt_len now includes the length of the tree representations, except
     * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
     */

    /* Determine the number of bit length codes to send. The pkzip format
     * requires that at least 4 bit length codes be sent. (appnote.txt says
     * 3 but the actual value used is 4.)
     */
    for(max_blindex = zip_BL_CODES-1; max_blindex >= 3; max_blindex--) {
    if(zip_bl_tree[zip_bl_order[max_blindex]].dl != 0) break;
    }
    /* Update opt_len to include the bit length tree and counts */
    zip_opt_len += 3*(max_blindex+1) + 5+5+4;
//    Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
//      encoder->opt_len, encoder->static_len));

    return max_blindex;
}

/* ==========================================================================
 * Send the header for a block using dynamic Huffman trees: the counts, the
 * lengths of the bit length codes, the literal tree and the distance tree.
 * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
 */
function zip_send_all_trees(lcodes, dcodes, blcodes) { // number of codes for each tree
    var rank; // index in bl_order

//    Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
//    Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
//      "too many codes");
//    Tracev((stderr, "\nbl counts: "));
    zip_send_bits(lcodes-257, 5); // not +255 as stated in appnote.txt
    zip_send_bits(dcodes-1,   5);
    zip_send_bits(blcodes-4,  4); // not -3 as stated in appnote.txt
    for(rank = 0; rank < blcodes; rank++) {
//      Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
    zip_send_bits(zip_bl_tree[zip_bl_order[rank]].dl, 3);
    }

    // send the literal tree
    zip_send_tree(zip_dyn_ltree,lcodes-1);

    // send the distance tree
    zip_send_tree(zip_dyn_dtree,dcodes-1);
}

/* ==========================================================================
 * Determine the best encoding for the current block: dynamic trees, static
 * trees or store, and output the encoded block to the zip file.
 */
function zip_flush_block(eof) { // true if this is the last block for a file
    var opt_lenb, static_lenb; // opt_len and static_len in bytes
    var max_blindex;    // index of last bit length code of non zero freq
    var stored_len; // length of input block

    stored_len = zip_strstart - zip_block_start;
    zip_flag_buf[zip_last_flags] = zip_flags; // Save the flags for the last 8 items

    // Construct the literal and distance trees
    zip_build_tree(zip_l_desc);
//    Tracev((stderr, "\nlit data: dyn %ld, stat %ld",
//      encoder->opt_len, encoder->static_len));

    zip_build_tree(zip_d_desc);
//    Tracev((stderr, "\ndist data: dyn %ld, stat %ld",
//      encoder->opt_len, encoder->static_len));
    /* At this point, opt_len and static_len are the total bit lengths of
     * the compressed block data, excluding the tree representations.
     */

    /* Build the bit length tree for the above two trees, and get the index
     * in bl_order of the last bit length code to send.
     */
    max_blindex = zip_build_bl_tree();

    // Determine the best encoding. Compute first the block length in bytes
    opt_lenb    = (zip_opt_len   +3+7)>>3;
    static_lenb = (zip_static_len+3+7)>>3;

//    Trace((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u dist %u ",
//     opt_lenb, encoder->opt_len,
//     static_lenb, encoder->static_len, stored_len,
//     encoder->last_lit, encoder->last_dist));

    if(static_lenb <= opt_lenb)
    opt_lenb = static_lenb;
    if(stored_len + 4 <= opt_lenb // 4: two words for the lengths
       && zip_block_start >= 0) {
    var i;

    /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
     * Otherwise we can't have processed more than WSIZE input bytes since
     * the last block flush, because compression would have been
     * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
     * transform a block into a stored block.
     */
    zip_send_bits((zip_STORED_BLOCK<<1)+eof, 3);  /* send block type */
    zip_bi_windup();         /* align on byte boundary */
    zip_put_short(stored_len);
    zip_put_short(~stored_len);

      // copy block
/*
      p = &window[block_start];
      for(i = 0; i < stored_len; i++)
    put_byte(p[i]);
*/
    for(i = 0; i < stored_len; i++)
        zip_put_byte(zip_window[zip_block_start + i]);

    } else if(static_lenb == opt_lenb) {
    zip_send_bits((zip_STATIC_TREES<<1)+eof, 3);
    zip_compress_block(zip_static_ltree, zip_static_dtree);
    } else {
    zip_send_bits((zip_DYN_TREES<<1)+eof, 3);
    zip_send_all_trees(zip_l_desc.max_code+1,
               zip_d_desc.max_code+1,
               max_blindex+1);
    zip_compress_block(zip_dyn_ltree, zip_dyn_dtree);
    }

    zip_init_block();

    if(eof != 0)
    zip_bi_windup();
}

/* ==========================================================================
 * Save the match info and tally the frequency counts. Return true if
 * the current block must be flushed.
 */
function zip_ct_tally(
    dist, // distance of matched string
    lc) { // match length-MIN_MATCH or unmatched char (if dist==0)
    zip_l_buf[zip_last_lit++] = lc;
    if(dist == 0) {
    // lc is the unmatched char
    zip_dyn_ltree[lc].fc++;
    } else {
    // Here, lc is the match length - MIN_MATCH
    dist--;         // dist = match distance - 1
//      Assert((ush)dist < (ush)MAX_DIST &&
//       (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
//       (ush)D_CODE(dist) < (ush)D_CODES,  "ct_tally: bad match");

    zip_dyn_ltree[zip_length_code[lc]+zip_LITERALS+1].fc++;
    zip_dyn_dtree[zip_D_CODE(dist)].fc++;

    zip_d_buf[zip_last_dist++] = dist;
    zip_flags |= zip_flag_bit;
    }
    zip_flag_bit <<= 1;

    // Output the flags if they fill a byte
    if((zip_last_lit & 7) == 0) {
    zip_flag_buf[zip_last_flags++] = zip_flags;
    zip_flags = 0;
    zip_flag_bit = 1;
    }
    // Try to guess if it is profitable to stop the current block here
    if(zip_compr_level > 2 && (zip_last_lit & 0xfff) == 0) {
    // Compute an upper bound for the compressed length
    var out_length = zip_last_lit * 8;
    var in_length = zip_strstart - zip_block_start;
    var dcode;

    for(dcode = 0; dcode < zip_D_CODES; dcode++) {
        out_length += zip_dyn_dtree[dcode].fc * (5 + zip_extra_dbits[dcode]);
    }
    out_length >>= 3;
//      Trace((stderr,"\nlast_lit %u, last_dist %u, in %ld, out ~%ld(%ld%%) ",
//       encoder->last_lit, encoder->last_dist, in_length, out_length,
//       100L - out_length*100L/in_length));
    if(zip_last_dist < parseInt(zip_last_lit/2) &&
       out_length < parseInt(in_length/2))
        return true;
    }
    return (zip_last_lit == zip_LIT_BUFSIZE-1 ||
        zip_last_dist == zip_DIST_BUFSIZE);
    /* We avoid equality with LIT_BUFSIZE because of wraparound at 64K
     * on 16 bit machines and because stored blocks are restricted to
     * 64K-1 bytes.
     */
}

  /* ==========================================================================
   * Send the block data compressed using the given Huffman trees
   */
function zip_compress_block(
    ltree,  // literal tree
    dtree) {    // distance tree
    var dist;       // distance of matched string
    var lc;     // match length or unmatched char (if dist == 0)
    var lx = 0;     // running index in l_buf
    var dx = 0;     // running index in d_buf
    var fx = 0;     // running index in flag_buf
    var flag = 0;   // current flags
    var code;       // the code to send
    var extra;      // number of extra bits to send

    if(zip_last_lit != 0) do {
    if((lx & 7) == 0)
        flag = zip_flag_buf[fx++];
    lc = zip_l_buf[lx++] & 0xff;
    if((flag & 1) == 0) {
        zip_SEND_CODE(lc, ltree); /* send a literal byte */
//  Tracecv(isgraph(lc), (stderr," '%c' ", lc));
    } else {
        // Here, lc is the match length - MIN_MATCH
        code = zip_length_code[lc];
        zip_SEND_CODE(code+zip_LITERALS+1, ltree); // send the length code
        extra = zip_extra_lbits[code];
        if(extra != 0) {
        lc -= zip_base_length[code];
        zip_send_bits(lc, extra); // send the extra length bits
        }
        dist = zip_d_buf[dx++];
        // Here, dist is the match distance - 1
        code = zip_D_CODE(dist);
//  Assert (code < D_CODES, "bad d_code");

        zip_SEND_CODE(code, dtree);   // send the distance code
        extra = zip_extra_dbits[code];
        if(extra != 0) {
        dist -= zip_base_dist[code];
        zip_send_bits(dist, extra);   // send the extra distance bits
        }
    } // literal or match pair ?
    flag >>= 1;
    } while(lx < zip_last_lit);

    zip_SEND_CODE(zip_END_BLOCK, ltree);
}

/* ==========================================================================
 * Send a value on a given number of bits.
 * IN assertion: length <= 16 and value fits in length bits.
 */
var zip_Buf_size = 16; // bit size of bi_buf
function zip_send_bits(
    value,  // value to send
    length) {   // number of bits
    /* If not enough room in bi_buf, use (valid) bits from bi_buf and
     * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
     * unused bits in value.
     */
    if(zip_bi_valid > zip_Buf_size - length) {
    zip_bi_buf |= (value << zip_bi_valid);
    zip_put_short(zip_bi_buf);
    zip_bi_buf = (value >> (zip_Buf_size - zip_bi_valid));
    zip_bi_valid += length - zip_Buf_size;
    } else {
    zip_bi_buf |= value << zip_bi_valid;
    zip_bi_valid += length;
    }
}

/* ==========================================================================
 * Reverse the first len bits of a code, using straightforward code (a faster
 * method would use a table)
 * IN assertion: 1 <= len <= 15
 */
function zip_bi_reverse(
    code,   // the value to invert
    len) {  // its bit length
    var res = 0;
    do {
    res |= code & 1;
    code >>= 1;
    res <<= 1;
    } while(--len > 0);
    return res >> 1;
}

/* ==========================================================================
 * Write out any remaining bits in an incomplete byte.
 */
function zip_bi_windup() {
    if(zip_bi_valid > 8) {
    zip_put_short(zip_bi_buf);
    } else if(zip_bi_valid > 0) {
    zip_put_byte(zip_bi_buf);
    }
    zip_bi_buf = 0;
    zip_bi_valid = 0;
}

function zip_qoutbuf() {
    if(zip_outcnt != 0) {
    var q, i;
    q = zip_new_queue();
    if(zip_qhead == null)
        zip_qhead = zip_qtail = q;
    else
        zip_qtail = zip_qtail.next = q;
    q.len = zip_outcnt - zip_outoff;
//      System.arraycopy(zip_outbuf, zip_outoff, q.ptr, 0, q.len);
    for(i = 0; i < q.len; i++)
        q.ptr[i] = zip_outbuf[zip_outoff + i];
    zip_outcnt = zip_outoff = 0;
    }
}

function zip_deflate(str, level) {
    var out, buff;
    var i, j;

    zip_deflate_data = str;
    zip_deflate_pos = 0;
    if(typeof level == "undefined")
    level = zip_DEFAULT_LEVEL;
    zip_deflate_start(level);

    buff = new Array(1024);
    out = "";
    while((i = zip_deflate_internal(buff, 0, buff.length)) > 0) {
    for(j = 0; j < i; j++)
        out += String.fromCharCode(buff[j]);
    }
    zip_deflate_data = null; // G.C.
    return out;
}