edgevpn/js/deflate.js

/* Copyright (C) 1999 Masanao Izumo <[email protected]>
* Version: 1.0.1
* LastModified: Dec 25 1999
*/

/* Interface:
* data = deflate(src);
*/
const deflate = (function () {
    /* 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;

    /* 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;
    }

    /* constant tables */
    var zip_extra_lbits = [
        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 = [
        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 = [
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 3, 7];
    var zip_bl_order = [16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15];
    var zip_configuration_table = [
        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)];


    /* 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;
        }
    }

    return function deflate(str, level) {
        var i, j;

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

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