local-scratch-vm/src/extensions/jg_prism/beatgammit-inflate.js

/* constant parameters */
var WSIZE = 32768, // Sliding Window size
    STORED_BLOCK = 0,
    STATIC_TREES = 1,
    DYN_TREES = 2,

    /* for inflate */
    lbits = 9, // bits in base literal/length lookup table
    dbits = 6, // bits in base distance lookup table

    /* variables (inflate) */
    slide,
    wp, // current position in slide
    fixed_tl = null, // inflate static
    fixed_td, // inflate static
    fixed_bl, // inflate static
    fixed_bd, // inflate static
    bit_buf, // bit buffer
    bit_len, // bits in bit buffer
    method,
    eof,
    copy_leng,
    copy_dist,
    tl, // literal length decoder table
    td, // literal distance decoder table
    bl, // number of bits decoded by tl
    bd, // number of bits decoded by td

    inflate_data,
    inflate_pos,


    /* constant tables (inflate) */
    MASK_BITS = [
        0x0000,
        0x0001, 0x0003, 0x0007, 0x000f, 0x001f, 0x003f, 0x007f, 0x00ff,
        0x01ff, 0x03ff, 0x07ff, 0x0fff, 0x1fff, 0x3fff, 0x7fff, 0xffff
    ],
    // Tables for deflate from PKZIP's appnote.txt.
    // Copy lengths for literal codes 257..285
    cplens = [
        3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
        35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0
    ],
    /* note: see note #13 above about the 258 in this list. */
    // Extra bits for literal codes 257..285
    cplext = [
        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, 99, 99 // 99==invalid
    ],
    // Copy offsets for distance codes 0..29
    cpdist = [
        1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
        257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
        8193, 12289, 16385, 24577
    ],
    // Extra bits for distance codes
    cpdext = [
        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
    ],
    // Order of the bit length code lengths
    border = [
        16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15
    ];
/* objects (inflate) */

function HuftList() {
    this.next = null;
    this.list = null;
}

function HuftNode() {
    this.e = 0; // number of extra bits or operation
    this.b = 0; // number of bits in this code or subcode

    // union
    this.n = 0; // literal, length base, or distance base
    this.t = null; // (HuftNode) pointer to next level of table
}

/*
* @param b-  code lengths in bits (all assumed <= BMAX)
* @param n- number of codes (assumed <= N_MAX)
* @param s- number of simple-valued codes (0..s-1)
* @param d- list of base values for non-simple codes
* @param e- list of extra bits for non-simple codes
* @param mm- maximum lookup bits
*/
function HuftBuild(b, n, s, d, e, mm) {
    this.BMAX = 16; // maximum bit length of any code
    this.N_MAX = 288; // maximum number of codes in any set
    this.status = 0; // 0: success, 1: incomplete table, 2: bad input
    this.root = null; // (HuftList) starting table
    this.m = 0; // maximum lookup bits, returns actual

    /* Given a list of code lengths and a maximum table size, make a set of
    tables to decode that set of codes. Return zero on success, one if
    the given code set is incomplete (the tables are still built in this
    case), two if the input is invalid (all zero length codes or an
    oversubscribed set of lengths), and three if not enough memory.
    The code with value 256 is special, and the tables are constructed
    so that no bits beyond that code are fetched when that code is
    decoded. */
    var a; // counter for codes of length k
    var c = [];
    var el; // length of EOB code (value 256)
    var f; // i repeats in table every f entries
    var g; // maximum code length
    var h; // table level
    var i; // counter, current code
    var j; // counter
    var k; // number of bits in current code
    var lx = [];
    var p; // pointer into c[], b[], or v[]
    var pidx; // index of p
    var q; // (HuftNode) points to current table
    var r = new HuftNode(); // table entry for structure assignment
    var u = [];
    var v = [];
    var w;
    var x = [];
    var xp; // pointer into x or c
    var y; // number of dummy codes added
    var z; // number of entries in current table
    var o;
    var tail; // (HuftList)

    tail = this.root = null;

    // bit length count table
    for (i = 0; i < this.BMAX + 1; i++) {
        c[i] = 0;
    }
    // stack of bits per table
    for (i = 0; i < this.BMAX + 1; i++) {
        lx[i] = 0;
    }
    // HuftNode[BMAX][]  table stack
    for (i = 0; i < this.BMAX; i++) {
        u[i] = null;
    }
    // values in order of bit length
    for (i = 0; i < this.N_MAX; i++) {
        v[i] = 0;
    }
    // bit offsets, then code stack
    for (i = 0; i < this.BMAX + 1; i++) {
        x[i] = 0;
    }

    // Generate counts for each bit length
    el = n > 256 ? b[256] : this.BMAX; // set length of EOB code, if any
    p = b; pidx = 0;
    i = n;
    do {
        c[p[pidx]]++; // assume all entries <= BMAX
        pidx++;
    } while (--i > 0);
    if (c[0] === n) { // null input--all zero length codes
        this.root = null;
        this.m = 0;
        this.status = 0;
        return;
    }

    // Find minimum and maximum length, bound *m by those
    for (j = 1; j <= this.BMAX; j++) {
        if (c[j] !== 0) {
            break;
        }
    }
    k = j; // minimum code length
    if (mm < j) {
        mm = j;
    }
    for (i = this.BMAX; i !== 0; i--) {
        if (c[i] !== 0) {
            break;
        }
    }
    g = i; // maximum code length
    if (mm > i) {
        mm = i;
    }

    // Adjust last length count to fill out codes, if needed
    for (y = 1 << j; j < i; j++, y <<= 1) {
        if ((y -= c[j]) < 0) {
            this.status = 2; // bad input: more codes than bits
            this.m = mm;
            return;
        }
    }
    if ((y -= c[i]) < 0) {
        this.status = 2;
        this.m = mm;
        return;
    }
    c[i] += y;

    // Generate starting offsets into the value table for each length
    x[1] = j = 0;
    p = c;
    pidx = 1;
    xp = 2;
    while (--i > 0) { // note that i == g from above
        x[xp++] = (j += p[pidx++]);
    }

    // Make a table of values in order of bit lengths
    p = b; pidx = 0;
    i = 0;
    do {
        if ((j = p[pidx++]) !== 0) {
            v[x[j]++] = i;
        }
    } while (++i < n);
    n = x[g]; // set n to length of v

    // Generate the Huffman codes and for each, make the table entries
    x[0] = i = 0; // first Huffman code is zero
    p = v; pidx = 0; // grab values in bit order
    h = -1; // no tables yet--level -1
    w = lx[0] = 0; // no bits decoded yet
    q = null; // ditto
    z = 0; // ditto

    // go through the bit lengths (k already is bits in shortest code)
    for (null; k <= g; k++) {
        a = c[k];
        while (a-- > 0) {
            // here i is the Huffman code of length k bits for value p[pidx]
            // make tables up to required level
            while (k > w + lx[1 + h]) {
                w += lx[1 + h]; // add bits already decoded
                h++;

                // compute minimum size table less than or equal to *m bits
                z = (z = g - w) > mm ? mm : z; // upper limit
                if ((f = 1 << (j = k - w)) > a + 1) { // try a k-w bit table
                    // too few codes for k-w bit table
                    f -= a + 1; // deduct codes from patterns left
                    xp = k;
                    while (++j < z) { // try smaller tables up to z bits
                        if ((f <<= 1) <= c[++xp]) {
                            break; // enough codes to use up j bits
                        }
                        f -= c[xp]; // else deduct codes from patterns
                    }
                }
                if (w + j > el && w < el) {
                    j = el - w; // make EOB code end at table
                }
                z = 1 << j; // table entries for j-bit table
                lx[1 + h] = j; // set table size in stack

                // allocate and link in new table
                q = [];
                for (o = 0; o < z; o++) {
                    q[o] = new HuftNode();
                }

                if (!tail) {
                    tail = this.root = new HuftList();
                } else {
                    tail = tail.next = new HuftList();
                }
                tail.next = null;
                tail.list = q;
                u[h] = q; // table starts after link

                /* connect to last table, if there is one */
                if (h > 0) {
                    x[h] = i; // save pattern for backing up
                    r.b = lx[h]; // bits to dump before this table
                    r.e = 16 + j; // bits in this table
                    r.t = q; // pointer to this table
                    j = (i & ((1 << w) - 1)) >> (w - lx[h]);
                    u[h - 1][j].e = r.e;
                    u[h - 1][j].b = r.b;
                    u[h - 1][j].n = r.n;
                    u[h - 1][j].t = r.t;
                }
            }

            // set up table entry in r
            r.b = k - w;
            if (pidx >= n) {
                r.e = 99; // out of values--invalid code
            } else if (p[pidx] < s) {
                r.e = (p[pidx] < 256 ? 16 : 15); // 256 is end-of-block code
                r.n = p[pidx++]; // simple code is just the value
            } else {
                r.e = e[p[pidx] - s]; // non-simple--look up in lists
                r.n = d[p[pidx++] - s];
            }

            // fill code-like entries with r //
            f = 1 << (k - w);
            for (j = i >> w; j < z; j += f) {
                q[j].e = r.e;
                q[j].b = r.b;
                q[j].n = r.n;
                q[j].t = r.t;
            }

            // backwards increment the k-bit code i
            for (j = 1 << (k - 1); (i & j) !== 0; j >>= 1) {
                i ^= j;
            }
            i ^= j;

            // backup over finished tables
            while ((i & ((1 << w) - 1)) !== x[h]) {
                w -= lx[h]; // don't need to update q
                h--;
            }
        }
    }

    /* return actual size of base table */
    this.m = lx[1];

    /* Return true (1) if we were given an incomplete table */
    this.status = ((y !== 0 && g !== 1) ? 1 : 0);
}


/* routines (inflate) */

function GET_BYTE() {
    if (inflate_data.length === inflate_pos) {
        return -1;
    }
    return inflate_data[inflate_pos++] & 0xff;
}

function NEEDBITS(n) {
    while (bit_len < n) {
        bit_buf |= GET_BYTE() << bit_len;
        bit_len += 8;
    }
}

function GETBITS(n) {
    return bit_buf & MASK_BITS[n];
}

function DUMPBITS(n) {
    bit_buf >>= n;
    bit_len -= n;
}

function inflate_codes(buff, off, size) {
    // inflate (decompress) the codes in a deflated (compressed) block.
    // Return an error code or zero if it all goes ok.
    var e; // table entry flag/number of extra bits
    var t; // (HuftNode) pointer to table entry
    var n;

    if (size === 0) {
        return 0;
    }

    // inflate the coded data
    n = 0;
    for (; ;) { // do until end of block
        NEEDBITS(bl);
        t = tl.list[GETBITS(bl)];
        e = t.e;
        while (e > 16) {
            if (e === 99) {
                return -1;
            }
            DUMPBITS(t.b);
            e -= 16;
            NEEDBITS(e);
            t = t.t[GETBITS(e)];
            e = t.e;
        }
        DUMPBITS(t.b);

        if (e === 16) { // then it's a literal
            wp &= WSIZE - 1;
            buff[off + n++] = slide[wp++] = t.n;
            if (n === size) {
                return size;
            }
            continue;
        }

        // exit if end of block
        if (e === 15) {
            break;
        }

        // it's an EOB or a length

        // get length of block to copy
        NEEDBITS(e);
        copy_leng = t.n + GETBITS(e);
        DUMPBITS(e);

        // decode distance of block to copy
        NEEDBITS(bd);
        t = td.list[GETBITS(bd)];
        e = t.e;

        while (e > 16) {
            if (e === 99) {
                return -1;
            }
            DUMPBITS(t.b);
            e -= 16;
            NEEDBITS(e);
            t = t.t[GETBITS(e)];
            e = t.e;
        }
        DUMPBITS(t.b);
        NEEDBITS(e);
        copy_dist = wp - t.n - GETBITS(e);
        DUMPBITS(e);

        // do the copy
        while (copy_leng > 0 && n < size) {
            copy_leng--;
            copy_dist &= WSIZE - 1;
            wp &= WSIZE - 1;
            buff[off + n++] = slide[wp++] = slide[copy_dist++];
        }

        if (n === size) {
            return size;
        }
    }

    method = -1; // done
    return n;
}

function inflate_stored(buff, off, size) {
    /* "decompress" an inflated type 0 (stored) block. */
    var n;

    // go to byte boundary
    n = bit_len & 7;
    DUMPBITS(n);

    // get the length and its complement
    NEEDBITS(16);
    n = GETBITS(16);
    DUMPBITS(16);
    NEEDBITS(16);
    if (n !== ((~bit_buf) & 0xffff)) {
        return -1; // error in compressed data
    }
    DUMPBITS(16);

    // read and output the compressed data
    copy_leng = n;

    n = 0;
    while (copy_leng > 0 && n < size) {
        copy_leng--;
        wp &= WSIZE - 1;
        NEEDBITS(8);
        buff[off + n++] = slide[wp++] = GETBITS(8);
        DUMPBITS(8);
    }

    if (copy_leng === 0) {
        method = -1; // done
    }
    return n;
}

function inflate_fixed(buff, off, size) {
    // decompress an inflated type 1 (fixed Huffman codes) block.  We should
    // either replace this with a custom decoder, or at least precompute the
    // Huffman tables.

    // if first time, set up tables for fixed blocks
    if (!fixed_tl) {
        var i; // temporary variable
        var l = []; // 288 length list for huft_build (initialized below)
        var h; // HuftBuild

        // literal table
        for (i = 0; i < 144; i++) {
            l[i] = 8;
        }
        for (null; i < 256; i++) {
            l[i] = 9;
        }
        for (null; i < 280; i++) {
            l[i] = 7;
        }
        for (null; i < 288; i++) { // make a complete, but wrong code set
            l[i] = 8;
        }
        fixed_bl = 7;

        h = new HuftBuild(l, 288, 257, cplens, cplext, fixed_bl);
        if (h.status !== 0) {
            console.error("HufBuild error: " + h.status);
            return -1;
        }
        fixed_tl = h.root;
        fixed_bl = h.m;

        // distance table
        for (i = 0; i < 30; i++) { // make an incomplete code set
            l[i] = 5;
        }
        fixed_bd = 5;

        h = new HuftBuild(l, 30, 0, cpdist, cpdext, fixed_bd);
        if (h.status > 1) {
            fixed_tl = null;
            console.error("HufBuild error: " + h.status);
            return -1;
        }
        fixed_td = h.root;
        fixed_bd = h.m;
    }

    tl = fixed_tl;
    td = fixed_td;
    bl = fixed_bl;
    bd = fixed_bd;
    return inflate_codes(buff, off, size);
}

function inflate_dynamic(buff, off, size) {
    // decompress an inflated type 2 (dynamic Huffman codes) block.
    var i; // temporary variables
    var j;
    var l; // last length
    var n; // number of lengths to get
    var t; // (HuftNode) literal/length code table
    var nb; // number of bit length codes
    var nl; // number of literal/length codes
    var nd; // number of distance codes
    var ll = [];
    var h; // (HuftBuild)

    // literal/length and distance code lengths
    for (i = 0; i < 286 + 30; i++) {
        ll[i] = 0;
    }

    // read in table lengths
    NEEDBITS(5);
    nl = 257 + GETBITS(5); // number of literal/length codes
    DUMPBITS(5);
    NEEDBITS(5);
    nd = 1 + GETBITS(5); // number of distance codes
    DUMPBITS(5);
    NEEDBITS(4);
    nb = 4 + GETBITS(4); // number of bit length codes
    DUMPBITS(4);
    if (nl > 286 || nd > 30) {
        return -1; // bad lengths
    }

    // read in bit-length-code lengths
    for (j = 0; j < nb; j++) {
        NEEDBITS(3);
        ll[border[j]] = GETBITS(3);
        DUMPBITS(3);
    }
    for (null; j < 19; j++) {
        ll[border[j]] = 0;
    }

    // build decoding table for trees--single level, 7 bit lookup
    bl = 7;
    h = new HuftBuild(ll, 19, 19, null, null, bl);
    if (h.status !== 0) {
        return -1; // incomplete code set
    }

    tl = h.root;
    bl = h.m;

    // read in literal and distance code lengths
    n = nl + nd;
    i = l = 0;
    while (i < n) {
        NEEDBITS(bl);
        t = tl.list[GETBITS(bl)];
        j = t.b;
        DUMPBITS(j);
        j = t.n;
        if (j < 16) { // length of code in bits (0..15)
            ll[i++] = l = j; // save last length in l
        } else if (j === 16) { // repeat last length 3 to 6 times
            NEEDBITS(2);
            j = 3 + GETBITS(2);
            DUMPBITS(2);
            if (i + j > n) {
                return -1;
            }
            while (j-- > 0) {
                ll[i++] = l;
            }
        } else if (j === 17) { // 3 to 10 zero length codes
            NEEDBITS(3);
            j = 3 + GETBITS(3);
            DUMPBITS(3);
            if (i + j > n) {
                return -1;
            }
            while (j-- > 0) {
                ll[i++] = 0;
            }
            l = 0;
        } else { // j === 18: 11 to 138 zero length codes
            NEEDBITS(7);
            j = 11 + GETBITS(7);
            DUMPBITS(7);
            if (i + j > n) {
                return -1;
            }
            while (j-- > 0) {
                ll[i++] = 0;
            }
            l = 0;
        }
    }

    // build the decoding tables for literal/length and distance codes
    bl = lbits;
    h = new HuftBuild(ll, nl, 257, cplens, cplext, bl);
    if (bl === 0) { // no literals or lengths
        h.status = 1;
    }
    if (h.status !== 0) {
        if (h.status !== 1) {
            return -1; // incomplete code set
        }
        // **incomplete literal tree**
    }
    tl = h.root;
    bl = h.m;

    for (i = 0; i < nd; i++) {
        ll[i] = ll[i + nl];
    }
    bd = dbits;
    h = new HuftBuild(ll, nd, 0, cpdist, cpdext, bd);
    td = h.root;
    bd = h.m;

    if (bd === 0 && nl > 257) { // lengths but no distances
        // **incomplete distance tree**
        return -1;
    }
    /*
    if (h.status === 1) {
        // **incomplete distance tree**
    }
    */
    if (h.status !== 0) {
        return -1;
    }

    // decompress until an end-of-block code
    return inflate_codes(buff, off, size);
}

function inflate_start() {
    if (!slide) {
        slide = []; // new Array(2 * WSIZE); // slide.length is never called
    }
    wp = 0;
    bit_buf = 0;
    bit_len = 0;
    method = -1;
    eof = false;
    copy_leng = copy_dist = 0;
    tl = null;
}

function inflate_internal(buff, off, size) {
    // decompress an inflated entry
    var n, i;

    n = 0;
    while (n < size) {
        if (eof && method === -1) {
            return n;
        }

        if (copy_leng > 0) {
            if (method !== STORED_BLOCK) {
                // STATIC_TREES or DYN_TREES
                while (copy_leng > 0 && n < size) {
                    copy_leng--;
                    copy_dist &= WSIZE - 1;
                    wp &= WSIZE - 1;
                    buff[off + n++] = slide[wp++] = slide[copy_dist++];
                }
            } else {
                while (copy_leng > 0 && n < size) {
                    copy_leng--;
                    wp &= WSIZE - 1;
                    NEEDBITS(8);
                    buff[off + n++] = slide[wp++] = GETBITS(8);
                    DUMPBITS(8);
                }
                if (copy_leng === 0) {
                    method = -1; // done
                }
            }
            if (n === size) {
                return n;
            }
        }

        if (method === -1) {
            if (eof) {
                break;
            }

            // read in last block bit
            NEEDBITS(1);
            if (GETBITS(1) !== 0) {
                eof = true;
            }
            DUMPBITS(1);

            // read in block type
            NEEDBITS(2);
            method = GETBITS(2);
            DUMPBITS(2);
            tl = null;
            copy_leng = 0;
        }

        switch (method) {
            case STORED_BLOCK:
                i = inflate_stored(buff, off + n, size - n);
                break;

            case STATIC_TREES:
                if (tl) {
                    i = inflate_codes(buff, off + n, size - n);
                } else {
                    i = inflate_fixed(buff, off + n, size - n);
                }
                break;

            case DYN_TREES:
                if (tl) {
                    i = inflate_codes(buff, off + n, size - n);
                } else {
                    i = inflate_dynamic(buff, off + n, size - n);
                }
                break;

            default: // error
                i = -1;
                break;
        }

        if (i === -1) {
            if (eof) {
                return 0;
            }
            return -1;
        }
        n += i;
    }
    return n;
}

function inflate(arr) {
    var buff = [], i;

    inflate_start();
    inflate_data = arr;
    inflate_pos = 0;

    do {
        i = inflate_internal(buff, buff.length, 1024);
    } while (i > 0);
    inflate_data = null; // G.C.
    return buff;
}

module.exports = inflate;