added lightweight zip utils

- deflate/inflate
- zip files
- gz files

src/mol-util/_spec/zip.spec.ts

+/**
+ * Copyright (c) 2020 mol* contributors, licensed under MIT, See LICENSE file for more info.
+ *
+ * @author Alexander Rose <alexander.rose@weirdbyte.de>
+ */
+
+import { deflate, inflate, parse, encode } from '../zip/zip'
+
+describe('zip', () => {
+    it('roundtrip deflate/inflate', () => {
+        const data = new Uint8Array([1, 2, 3, 4, 5, 6, 7])
+        const deflated = deflate(data)
+        console.log(deflated)
+        const inflated = inflate(deflated)
+        console.log(inflated)
+    })
+
+    it('roundtrip zip', () => {
+        const zipped = encode({
+            'test.foo': new Uint8Array([1, 2, 3, 4, 5, 6, 7])
+        })
+        console.log(zipped)
+        const unzipped = parse(zipped)
+        console.log(unzipped)
+    })
+})
\ No newline at end of file

src/mol-util/zip/bin.ts

+/**
+ * Copyright (c) 2020 mol* contributors, licensed under MIT, See LICENSE file for more info.
+ *
+ * @author Alexander Rose <alexander.rose@weirdbyte.de>
+ *
+ * ported from https://github.com/photopea/UZIP.js/blob/master/UZIP.js
+ * MIT License, Copyright (c) 2018 Photopea
+ */
+
+export function toUint32(x: number) {
+    return x >>> 0
+}
+export function toInt32(x: number) {
+    return x >> 0
+}
+
+export function readUshort(buff: Uint8Array, p: number) {
+    return (buff[p]) | (buff[p+1]<<8);
+}
+
+export function writeUshort(buff: Uint8Array, p: number, n: number) {
+    buff[p] = (n)&255;  buff[p+1] = (n>>8)&255;
+}
+
+export function readUint(buff: Uint8Array, p: number) {
+    return (buff[p+3]*(256*256*256)) + ((buff[p+2]<<16) | (buff[p+1]<< 8) | buff[p]);
+}
+
+export function writeUint(buff: Uint8Array, p: number, n: number) {
+    buff[p] = n&255;
+    buff[p+1] = (n>>8)&255;
+    buff[p+2] = (n>>16)&255;
+    buff[p+3] = (n>>24)&255;
+}
+
+function readASCII(buff: Uint8Array, p: number, l: number){
+    let s = '';
+    for(let i=0; i<l; i++) s += String.fromCharCode(buff[p+i]);
+    return s;
+}
+
+// function writeASCII(data: Uint8Array, p: number, s: string){
+//     for(let i=0; i<s.length; i++) data[p+i] = s.charCodeAt(i);
+// }
+
+function pad(n: string) {
+    return n.length < 2 ? '0' + n : n;
+}
+
+export function readUTF8(buff: Uint8Array, p: number, l: number) {
+    let s = '', ns;
+    for(let i = 0; i<l; i++) s += '%' + pad(buff[p+i].toString(16));
+    try {
+        ns = decodeURIComponent(s);
+    } catch(e) {
+        return readASCII(buff, p, l);
+    }
+    return ns;
+}
+
+export function writeUTF8(buff: Uint8Array, p: number, str: string) {
+    const strl = str.length
+    let i = 0;
+    for(let ci = 0; ci<strl; ci++) {
+        const code = str.charCodeAt(ci);
+        if((code&(0xffffffff-(1<< 7)+1)) === 0) {
+            buff[p+i] = (     code     );
+            i++;
+        } else if((code&(0xffffffff-(1<<11)+1)) === 0) {
+            buff[p+i] = (192|(code>> 6));
+            buff[p+i+1] = (128|((code>> 0)&63));
+            i+=2;
+        } else if((code&(0xffffffff-(1<<16)+1)) === 0) {
+            buff[p+i] = (224|(code>>12));
+            buff[p+i+1] = (128|((code>> 6)&63));
+            buff[p+i+2] = (128|((code>>0)&63));
+            i+=3;
+        } else if((code&(0xffffffff-(1<<21)+1)) === 0) {
+            buff[p+i] = (240|(code>>18));
+            buff[p+i+1] = (128|((code>>12)&63));
+            buff[p+i+2] = (128|((code>>6)&63));
+            buff[p+i+3] = (128|((code>>0)&63));
+            i+=4;
+        } else throw 'e';
+    }
+    return i;
+}
+
+export function sizeUTF8(str: string) {
+    const strl = str.length
+    let i = 0;
+    for(let ci = 0; ci < strl; ci++) {
+        const code = str.charCodeAt(ci);
+        if     ((code&(0xffffffff-(1<< 7)+1)) === 0) {  i++ ;  }
+        else if((code&(0xffffffff-(1<<11)+1)) === 0) {  i+=2;  }
+        else if((code&(0xffffffff-(1<<16)+1)) === 0) {  i+=3;  }
+        else if((code&(0xffffffff-(1<<21)+1)) === 0) {  i+=4;  }
+        else throw 'e';
+    }
+    return i;
+}

src/mol-util/zip/checksum.ts

+/**
+ * Copyright (c) 2020 mol* contributors, licensed under MIT, See LICENSE file for more info.
+ *
+ * @author Alexander Rose <alexander.rose@weirdbyte.de>
+ *
+ * ported from https://github.com/photopea/UZIP.js/blob/master/UZIP.js
+ * MIT License, Copyright (c) 2018 Photopea
+ */
+
+const CrcTable = (function() {
+    const tab = new Uint32Array(256);
+    for (let n=0; n<256; n++) {
+        let c = n;
+        for (let k=0; k<8; k++) {
+            if (c & 1)  c = 0xedb88320 ^ (c >>> 1);
+            else        c = c >>> 1;
+        }
+        tab[n] = c;
+    }
+    return tab;
+})()
+
+function _crc(c: number, buf: Uint8Array, off: number, len: number) {
+    for (let i = 0; i<len; i++)  {
+        c = CrcTable[(c ^ buf[off+i]) & 0xff] ^ (c >>> 8);
+    }
+    return c;
+}
+
+export function crc(b: Uint8Array, o: number, l: number)  {
+    return _crc(0xffffffff, b, o, l) ^ 0xffffffff;
+}
+
+export function adler(data: Uint8Array, o: number, len: number) {
+    let a = 1, b = 0;
+    let off = o
+    const end = o+len;
+    while(off < end) {
+        const eend = Math.min(off + 5552, end);
+        while(off < eend) {
+            a += data[off++];
+            b += a;
+        }
+        a = a % 65521;
+        b = b % 65521;
+    }
+    return (b << 16) | a;
+}
\ No newline at end of file

src/mol-util/zip/deflate.ts

+/**
+ * Copyright (c) 2020 mol* contributors, licensed under MIT, See LICENSE file for more info.
+ *
+ * @author Alexander Rose <alexander.rose@weirdbyte.de>
+ *
+ * ported from https://github.com/photopea/UZIP.js/blob/master/UZIP.js
+ * MIT License, Copyright (c) 2018 Photopea
+ */
+
+import { NumberArray } from '../type-helpers';
+import { _hufTree } from './huffman';
+import { U, revCodes, makeCodes } from './util';
+
+export function _deflateRaw(data: Uint8Array, out: Uint8Array, opos: number, lvl: number) {
+    const opts = [
+        /*
+            ush good_length; /* reduce lazy search above this match length
+            ush max_lazy;    /* do not perform lazy search above this match length
+            ush nice_length; /* quit search above this match length
+        */
+        /*      good lazy nice chain */
+        /* 0 */ [ 0,   0,   0,    0, 0], /* store only */
+        /* 1 */ [ 4,   4,   8,    4, 0], /* max speed, no lazy matches */
+        /* 2 */ [ 4,   5,  16,    8, 0],
+        /* 3 */ [ 4,   6,  16,   16, 0],
+
+        /* 4 */ [ 4,  10,  16,   32, 0], /* lazy matches */
+        /* 5 */ [ 8,  16,  32,   32, 0],
+        /* 6 */ [ 8,  16, 128,  128, 0],
+        /* 7 */ [ 8,  32, 128,  256, 0],
+        /* 8 */ [32, 128, 258, 1024, 1],
+        /* 9 */ [32, 258, 258, 4096, 1] /* max compression */
+    ]
+
+    const opt = opts[lvl];
+
+    let i = 0, pos = opos<<3, cvrd = 0
+    const dlen = data.length;
+
+    if(lvl === 0) {
+        while(i < dlen) {
+            const len = Math.min(0xffff, dlen-i);
+            _putsE(out, pos, (i + len === dlen ? 1 : 0));
+            pos = _copyExact(data, i, len, out, pos + 8);
+            i += len;
+        }
+        return pos>>>3;
+    }
+
+    const { lits, strt, prev } = U
+    let li = 0, lc = 0, bs = 0, ebits = 0, c = 0, nc = 0;  // last_item, literal_count, block_start
+    if(dlen > 2) {
+        nc=_hash(data,0);
+        strt[nc]=0;
+    }
+
+    // let nmch = 0
+    // let nmci = 0
+
+    for(i = 0; i<dlen; i++)  {
+        c = nc;
+        //*
+        if(i + 1 < dlen - 2) {
+            nc = _hash(data, i+1);
+            const ii = ((i+1)&0x7fff);
+            prev[ii] = strt[nc];
+            strt[nc] = ii;
+        } // */
+        if(cvrd <= i) {
+            if((li > 14000 || lc > 26697) && (dlen - i) > 100) {
+                if(cvrd < i) {
+                    lits[li] = i - cvrd;
+                    li += 2;
+                    cvrd = i;
+                }
+                pos = _writeBlock(((i === dlen - 1) || (cvrd === dlen)) ? 1 : 0, lits, li, ebits, data, bs, i - bs, out, pos);
+                li = lc = ebits = 0;
+                bs = i;
+            }
+
+            let mch = 0;
+            // if(nmci==i) mch= nmch;  else
+            if(i < dlen-2) {
+                mch = _bestMatch(data, i, prev, c, Math.min(opt[2],dlen-i), opt[3]);
+            }
+            /*
+            if(mch!=0 && opt[4]==1 && (mch>>>16)<opt[1] && i+1<dlen-2) {
+                nmch = UZIP.F._bestMatch(data, i+1, prev, nc, opt[2], opt[3]);  nmci=i+1;
+                //var mch2 = UZIP.F._bestMatch(data, i+2, prev, nnc);  //nmci=i+1;
+                if((nmch>>>16)>(mch>>>16)) mch=0;
+            }//*/
+            // const len = mch>>>16, dst = mch & 0xffff;  // if(i-dst<0) throw "e";
+            if(mch !== 0) {
+                const len = mch>>>16, dst = mch&0xffff;  // if(i-dst<0) throw "e";
+                const lgi = _goodIndex(len, U.of0);  U.lhst[257+lgi]++;
+                const dgi = _goodIndex(dst, U.df0);  U.dhst[    dgi]++;  ebits += U.exb[lgi] + U.dxb[dgi];
+                lits[li] = (len<<23)|(i-cvrd);  lits[li+1] = (dst<<16)|(lgi<<8)|dgi;  li+=2;
+                cvrd = i + len;
+            }
+            else {	U.lhst[data[i]]++;  }
+            lc++;
+        }
+    }
+    if(bs !== i || data.length === 0) {
+        if(cvrd < i) {
+            lits[li]=i-cvrd;
+            li+=2;
+            cvrd=i;
+        }
+        pos = _writeBlock(1, lits, li, ebits, data, bs, i-bs, out, pos);
+        li=0;
+        lc=0;
+        li = lc = ebits=0;
+        bs=i;
+    }
+    while((pos&7) !== 0) pos++;
+    return pos>>>3;
+}
+
+function _bestMatch(data: Uint8Array, i: number, prev: Uint16Array, c: number, nice: number, chain: number) {
+    let ci = (i&0x7fff), pi=prev[ci];
+    // console.log("----", i);
+    let dif = ((ci-pi + (1<<15)) & 0x7fff);
+    if(pi === ci || c !== _hash(data,i-dif)) return 0;
+    let tl=0, td=0;  // top length, top distance
+    const dlim = Math.min(0x7fff, i);
+    while(dif<=dlim && --chain !== 0 && pi !== ci /* && c==UZIP.F._hash(data,i-dif)*/) {
+        if(tl === 0 || (data[i+tl] === data[i+tl-dif])) {
+            let cl = _howLong(data, i, dif);
+            if(cl>tl) {
+                tl=cl;  td=dif;  if(tl>=nice) break;    //*
+                if(dif+2<cl) cl = dif+2;
+                let maxd = 0; // pi does not point to the start of the word
+                for(let j=0; j<cl-2; j++) {
+                    const ei =  (i-dif+j+ (1<<15)) & 0x7fff;
+                    const li = prev[ei];
+                    const curd = (ei-li + (1<<15)) & 0x7fff;
+                    if(curd>maxd) {  maxd=curd;  pi = ei; }
+                }
+            }
+        }
+
+        ci=pi;  pi = prev[ci];
+        dif += ((ci-pi + (1<<15)) & 0x7fff);
+    }
+    return (tl<<16)|td;
+}
+
+function _howLong(data: Uint8Array, i: number, dif: number) {
+    if(data[i] !== data[i-dif] || data[i+1] !== data[i+1-dif] || data[i+2] !== data[i+2-dif]) return 0;
+    const oi=i, l = Math.min(data.length, i+258);
+    i+=3;
+    // while(i+4<l && data[i]==data[i-dif] && data[i+1]==data[i+1-dif] && data[i+2]==data[i+2-dif] && data[i+3]==data[i+3-dif]) i+=4;
+    while(i<l && data[i] === data[i-dif]) i++;
+    return i-oi;
+}
+
+function _hash(data: Uint8Array, i: number) {
+    return (((data[i]<<8) | data[i+1])+(data[i+2]<<4))&0xffff;
+    // var hash_shift = 0, hash_mask = 255;
+    // var h = data[i+1] % 251;
+    // h = (((h << 8) + data[i+2]) % 251);
+    // h = (((h << 8) + data[i+2]) % 251);
+    // h = ((h<<hash_shift) ^ (c) ) & hash_mask;
+    // return h | (data[i]<<8);
+    // return (data[i] | (data[i+1]<<8));
+}
+
+function _writeBlock(BFINAL: number, lits: Uint32Array, li: number, ebits: number, data: Uint8Array, o0: number, l0: number, out: Uint8Array, pos: number) {
+    U.lhst[256]++;
+    const [ ML, MD, MH, numl, numd, numh, lset, dset ] = getTrees()
+
+    const cstSize = (((pos+3)&7) === 0 ? 0 : 8-((pos+3)&7)) + 32 + (l0<<3);
+    const fxdSize = ebits + contSize(U.fltree, U.lhst) + contSize(U.fdtree, U.dhst);
+    let dynSize = ebits + contSize(U.ltree , U.lhst) + contSize(U.dtree , U.dhst);
+    dynSize += 14 + 3 * numh + contSize(U.itree, U.ihst) + (U.ihst[16]*2 + U.ihst[17]*3 + U.ihst[18]*7);
+
+    for(let j=0; j<286; j++) U.lhst[j]=0;
+    for(let j=0; j<30; j++) U.dhst[j]=0;
+    for(let j=0; j<19; j++) U.ihst[j]=0;
+
+    const BTYPE = (cstSize<fxdSize && cstSize<dynSize) ? 0 : ( fxdSize<dynSize ? 1 : 2 );
+    _putsF(out, pos, BFINAL);
+    _putsF(out, pos+1, BTYPE);
+    pos+=3;
+
+    // let opos = pos;
+    if(BTYPE === 0) {
+        while((pos&7) !== 0) pos++;
+        pos = _copyExact(data, o0, l0, out, pos);
+    } else {
+        let ltree: number[], dtree: number[];
+        if(BTYPE === 1) {
+            ltree=U.fltree;  dtree=U.fdtree;
+        } else if(BTYPE === 2) {
+            makeCodes(U.ltree, ML);  revCodes(U.ltree, ML);
+            makeCodes(U.dtree, MD);  revCodes(U.dtree, MD);
+            makeCodes(U.itree, MH);  revCodes(U.itree, MH);
+
+            ltree = U.ltree;  dtree = U.dtree;
+
+            _putsE(out, pos,numl-257);  pos+=5;  // 286
+            _putsE(out, pos,numd-  1);  pos+=5;  // 30
+            _putsE(out, pos,numh-  4);  pos+=4;  // 19
+
+            for(let i=0; i<numh; i++) _putsE(out, pos+i*3, U.itree[(U.ordr[i]<<1)+1]);
+            pos+=3* numh;
+            pos = _codeTiny(lset, U.itree, out, pos);
+            pos = _codeTiny(dset, U.itree, out, pos);
+        } else {
+            throw new Error(`unknown BTYPE ${BTYPE}`)
+        }
+
+        let off=o0;
+        for(let si=0; si<li; si+=2) {
+            const qb=lits[si], len=(qb>>>23), end = off+(qb&((1<<23)-1));
+            while(off<end) pos = _writeLit(data[off++], ltree, out, pos);
+
+            if(len !== 0) {
+                const qc = lits[si+1], dst=(qc>>16), lgi=(qc>>8)&255, dgi=(qc&255);
+                pos = _writeLit(257+lgi, ltree, out, pos);
+                _putsE(out, pos, len-U.of0[lgi]);  pos+=U.exb[lgi];
+
+                pos = _writeLit(dgi, dtree, out, pos);
+                _putsF(out, pos, dst-U.df0[dgi]);  pos+=U.dxb[dgi];  off+=len;
+            }
+        }
+        pos = _writeLit(256, ltree, out, pos);
+    }
+    // console.log(pos-opos, fxdSize, dynSize, cstSize);
+    return pos;
+}
+
+function _copyExact(data: Uint8Array, off: number, len: number, out: Uint8Array, pos: number) {
+    let p8 = (pos>>>3);
+    out[p8]=(len);
+    out[p8+1]=(len>>>8);
+    out[p8+2]=255-out[p8];
+    out[p8+3]=255-out[p8+1];
+    p8+=4;
+    out.set(new Uint8Array(data.buffer, off, len), p8);
+    // for(var i=0; i<len; i++) out[p8+i]=data[off+i];
+    return pos + ((len+4)<<3);
+}
+
+
+/*
+    Interesting facts:
+    - decompressed block can have bytes, which do not occur in a Huffman tree (copied from the previous block by reference)
+*/
+
+function getTrees() {
+    const ML = _hufTree(U.lhst, U.ltree, 15);
+    const MD = _hufTree(U.dhst, U.dtree, 15);
+    const lset: number[] = []
+    const numl = _lenCodes(U.ltree, lset);
+    const dset: number[] = []
+    const numd = _lenCodes(U.dtree, dset);
+    for(let i=0; i<lset.length; i+=2) U.ihst[lset[i]]++;
+    for(let i=0; i<dset.length; i+=2) U.ihst[dset[i]]++;
+    const MH = _hufTree(U.ihst, U.itree,  7);
+    let numh = 19;
+    while(numh>4 && U.itree[(U.ordr[numh-1]<<1)+1] === 0) numh--;
+    return [ML, MD, MH, numl, numd, numh, lset, dset] as const;
+}
+
+function contSize(tree: number[], hst: NumberArray) {
+    let s=0;
+    for(let i=0; i<hst.length; i++) s+= hst[i]*tree[(i<<1)+1];
+    return s;
+}
+
+function _codeTiny(set: number[], tree: number[], out: Uint8Array, pos: number) {
+    for(let i=0; i<set.length; i+=2) {
+        const l = set[i], rst = set[i+1];  // console.log(l, pos, tree[(l<<1)+1]);
+        pos = _writeLit(l, tree, out, pos);
+        const rsl = l === 16 ? 2 : (l === 17 ? 3 : 7);
+        if(l>15) {
+            _putsE(out, pos, rst);
+            pos+=rsl;
+        }
+    }
+    return pos;
+}
+
+
+function _lenCodes(tree: number[], set: number[]) {
+    let len = tree.length;
+    while(len !== 2 && tree[len-1] === 0) len-=2;  // when no distances, keep one code with length 0
+    for(let i=0; i<len; i+=2) {
+        const l = tree[i+1], nxt = (i+3<len ? tree[i+3]:-1),  nnxt = (i+5<len ? tree[i+5]:-1),  prv = (i === 0 ? -1 : tree[i-1]);
+        if(l === 0 && nxt === l && nnxt === l) {
+            let lz = i+5;
+            while(lz+2<len && tree[lz+2] === l) lz+=2;
+            const zc = Math.min((lz+1-i)>>>1, 138);
+            if(zc<11) set.push(17, zc-3);
+            else set.push(18, zc-11);
+            i += zc*2-2;
+        } else if(l === prv && nxt === l && nnxt === l) {
+            let lz = i+5;
+            while(lz+2<len && tree[lz+2] === l) lz+=2;
+            const zc = Math.min((lz+1-i)>>>1, 6);
+            set.push(16, zc-3);
+            i += zc*2-2;
+        }
+        else set.push(l, 0);
+    }
+    return len>>>1;
+}
+
+function _goodIndex(v: number, arr: number[]) {
+    let i=0;
+    if(arr[i|16]<=v) i|=16;
+    if(arr[i|8]<=v) i|=8;
+    if(arr[i|4]<=v) i|=4;
+    if(arr[i|2]<=v) i|=2;
+    if(arr[i|1]<=v) i|=1;
+    return i;
+}
+
+function _writeLit(ch: number, ltree: number[], out: Uint8Array, pos: number) {
+    _putsF(out, pos, ltree[ch<<1]);
+    return pos+ltree[(ch<<1)+1];
+}
+
+function _putsE(dt: NumberArray, pos: number, val: number) {
+    val = val<<(pos&7);
+    const o=(pos>>>3);
+    dt[o]|=val;
+    dt[o+1]|=(val>>>8);
+}
+
+function _putsF(dt: NumberArray, pos: number, val: number) {
+    val = val<<(pos&7);
+    const o=(pos>>>3);
+    dt[o]|=val;
+    dt[o+1]|=(val>>>8);
+    dt[o+2]|=(val>>>16);
+}

src/mol-util/zip/huffman.ts

+/**
+ * Copyright (c) 2020 mol* contributors, licensed under MIT, See LICENSE file for more info.
+ *
+ * @author Alexander Rose <alexander.rose@weirdbyte.de>
+ *
+ * ported from https://github.com/photopea/UZIP.js/blob/master/UZIP.js
+ * MIT License, Copyright (c) 2018 Photopea
+ */
+
+import { NumberArray } from '../type-helpers';
+
+export type HufTree = {
+    lit: number,
+    f: number,
+    l?: HufTree,
+    r?: HufTree,
+    d: number
+}
+export function _hufTree(hst: NumberArray, tree: number[], MAXL: number) {
+    const list: HufTree[] = []
+    const hl = hst.length, tl=tree.length
+    for(let i=0; i<tl; i+=2) {
+        tree[i]=0;
+        tree[i+1]=0;
+    }
+    for(let i=0; i<hl; i++) if(hst[i] !== 0) list.push({ lit: i, f: hst[i], d: undefined as any });
+    const end = list.length, l2=list.slice(0);
+    if(end === 0) return 0;  // empty histogram (usually for dist)
+    if(end === 1) {
+        const lit = list[0].lit, l2 = lit === 0 ? 1 : 0;
+        tree[(lit<<1)+1]=1;
+        tree[(l2<<1)+1]=1;
+        return 1;
+    }
+    list.sort(function(a,b){return a.f - b.f;});
+    let a=list[0], b=list[1], i0=0, i1=1, i2=2;
+    list[0] = {
+        lit: -1,
+        f: a.f + b.f,
+        l: a,
+        r: b,
+        d: 0
+    };
+    while(i1 !== end-1) {
+        if(i0 !== i1 && (i2 === end || list[i0].f<list[i2].f)) {
+            a=list[i0++];
+        } else {
+            a=list[i2++];
+        }
+        if(i0 !== i1 && (i2 === end || list[i0].f<list[i2].f)) {
+            b=list[i0++];
+        } else {
+            b=list[i2++];
+        }
+        list[i1++] = {
+            lit: -1,
+            f: a.f + b.f,
+            l: a,
+            r: b,
+            d: undefined as any
+        };
+    }
+    let maxl = setDepth(list[i1-1], 0);
+    if(maxl > MAXL) {
+        restrictDepth(l2, MAXL, maxl);
+        maxl = MAXL;
+    }
+    for(let i=0; i<end; i++) tree[(l2[i].lit<<1)+1] = l2[i].d;
+    return maxl;
+}
+
+function setDepth(t: HufTree, d: number): number {
+    if(t.lit !== -1) {
+        t.d = d;
+        return d;
+    }
+    return Math.max(setDepth(t.l!, d+1), setDepth(t.r!, d+1));
+}
+
+function restrictDepth(dps: HufTree[], MD: number, maxl: number) {
+    let i=0, bCost=1<<(maxl-MD), dbt=0;
+    dps.sort(function(a: HufTree, b: HufTree){return b.d === a.d ? a.f - b.f : b.d - a.d;});
+
+    for(i=0; i<dps.length; i++) {
+        if(dps[i].d>MD) {
+            const od=dps[i].d;
+            dps[i].d=MD;
+            dbt+=bCost-(1<<(maxl-od));
+        } else {
+            break;
+        }
+    }
+    dbt = dbt>>>(maxl-MD);
+    while(dbt>0) {
+        const od=dps[i].d;
+        if(od<MD) {
+            dps[i].d++;
+            dbt-=(1<<(MD-od-1));
+        } else {
+            i++;
+        }
+    }
+    for(; i>=0; i--) {
+        if(dps[i].d === MD && dbt<0) {
+            dps[i].d--;
+            dbt++;
+        }
+    }
+    if(dbt !== 0) console.log('debt left');
+}
\ No newline at end of file

src/mol-util/zip/inflate.ts

+/**
+ * Copyright (c) 2020 mol* contributors, licensed under MIT, See LICENSE file for more info.
+ *
+ * @author Alexander Rose <alexander.rose@weirdbyte.de>
+ *
+ * ported from https://github.com/photopea/UZIP.js/blob/master/UZIP.js
+ * MIT License, Copyright (c) 2018 Photopea
+ */
+
+import { NumberArray } from '../type-helpers';
+import { U, makeCodes, codes2map } from './util';
+
+export function _inflate(data: Uint8Array, buf?: Uint8Array) {
+    if(data[0] === 3 && data[1] === 0) return (buf ? buf : new Uint8Array(0));
+    // var F=UZIP.F, bitsF = F._bitsF, bitsE = F._bitsE, decodeTiny = F._decodeTiny, makeCodes = F.makeCodes, codes2map=F.codes2map, get17 = F._get17;
+    // var U = F.U;
+
+    const noBuf = buf === undefined;
+    if(buf === undefined) buf = new Uint8Array((data.length>>>2)<<3);
+
+    let BFINAL=0, BTYPE=0, HLIT=0, HDIST=0, HCLEN=0, ML=0, MD=0;
+    let off = 0, pos = 0;
+    let lmap, dmap;
+
+    while(BFINAL === 0) {
+        BFINAL = _bitsF(data, pos  , 1);
+        BTYPE  = _bitsF(data, pos+1, 2);
+        pos+=3;
+
+        if(BTYPE === 0) {
+            if((pos&7) !== 0) pos+=8-(pos&7);
+            const p8 = (pos>>>3)+4, len = data[p8-4]|(data[p8-3]<<8);  // console.log(len);//bitsF(data, pos, 16),
+            if(noBuf) buf=_check(buf, off+len);
+            buf.set(new Uint8Array(data.buffer, data.byteOffset+p8, len), off);
+            // for(var i=0; i<len; i++) buf[off+i] = data[p8+i];
+            // for(var i=0; i<len; i++) if(buf[off+i] != data[p8+i]) throw "e";
+            pos = ((p8+len)<<3);  off+=len;  continue;
+        }
+        if(noBuf) buf=_check(buf, off+(1<<17));  // really not enough in many cases (but PNG and ZIP provide buffer in advance)
+        if(BTYPE === 1) {
+            lmap = U.flmap;
+            dmap = U.fdmap;
+            ML = (1<<9)-1;
+            MD = (1<<5)-1;
+        } else if(BTYPE === 2) {
+            HLIT  = _bitsE(data, pos   , 5)+257;
+            HDIST = _bitsE(data, pos+ 5, 5)+  1;
+            HCLEN = _bitsE(data, pos+10, 4)+  4;  pos+=14;
+            // const ppos = pos;
+            for(let i=0; i<38; i+=2) {
+                U.itree[i]=0;
+                U.itree[i+1]=0;
+            }
+            let tl = 1;
+            for(let i=0; i<HCLEN; i++) {
+                const l=_bitsE(data, pos+i*3, 3);
+                U.itree[(U.ordr[i]<<1)+1] = l;
+                if(l>tl) tl = l;
+            }
+            pos+=3*HCLEN;  // console.log(itree);
+            makeCodes(U.itree, tl);
+            codes2map(U.itree, tl, U.imap);
+
+            lmap = U.lmap;  dmap = U.dmap;
+
+            pos = _decodeTiny(U.imap, (1<<tl)-1, HLIT+HDIST, data, pos, U.ttree);
+            const mx0 = _copyOut(U.ttree,    0, HLIT , U.ltree);  ML = (1<<mx0)-1;
+            const mx1 = _copyOut(U.ttree, HLIT, HDIST, U.dtree);  MD = (1<<mx1)-1;
+
+            // var ml = decodeTiny(U.imap, (1<<tl)-1, HLIT , data, pos, U.ltree); ML = (1<<(ml>>>24))-1;  pos+=(ml&0xffffff);
+            makeCodes(U.ltree, mx0);
+            codes2map(U.ltree, mx0, lmap);
+
+            // var md = decodeTiny(U.imap, (1<<tl)-1, HDIST, data, pos, U.dtree); MD = (1<<(md>>>24))-1;  pos+=(md&0xffffff);
+            makeCodes(U.dtree, mx1);
+            codes2map(U.dtree, mx1, dmap);
+        } else {
+            throw new Error(`unknown BTYPE ${BTYPE}`)
+        }
+
+        // var ooff=off, opos=pos;
+        while(true) {
+            const code = lmap[_get17(data, pos) & ML];
+            pos += code&15;
+            const lit = code >>> 4;  // U.lhst[lit]++;
+            if((lit >>> 8) === 0) {
+                buf[off++] = lit;
+            } else if(lit === 256) {
+                break;
+            } else {
+                let end = off+lit-254;
+                if(lit > 264) {
+                    const ebs = U.ldef[lit-257];
+                    end = off + (ebs>>>3) + _bitsE(data, pos, ebs&7);
+                    pos += ebs&7;
+                }
+                // UZIP.F.dst[end-off]++;
+
+                const dcode = dmap[_get17(data, pos) & MD];  pos += dcode&15;
+                const dlit = dcode>>>4;
+                const dbs = U.ddef[dlit], dst = (dbs>>>4) + _bitsF(data, pos, dbs&15);  pos += dbs&15;
+
+                // var o0 = off-dst, stp = Math.min(end-off, dst);
+                // if(stp>20) while(off<end) {  buf.copyWithin(off, o0, o0+stp);  off+=stp;  }  else
+                // if(end-dst<=off) buf.copyWithin(off, off-dst, end-dst);  else
+                // if(dst==1) buf.fill(buf[off-1], off, end);  else
+                if(noBuf) buf = _check(buf, off+(1<<17));
+                while(off<end) {
+                    buf[off]=buf[off++-dst];
+                    buf[off]=buf[off++-dst];
+                    buf[off]=buf[off++-dst];
+                    buf[off]=buf[off++-dst];
+                }
+                off=end;
+                // while(off!=end) {  buf[off]=buf[off++-dst];  }
+            }
+        }
+        // console.log(off-ooff, (pos-opos)>>>3);
+    }
+    // console.log(UZIP.F.dst);
+    // console.log(tlen, dlen, off-tlen+tcnt);
+    return buf.length === off ? buf : buf.slice(0, off);
+}
+
+function _check(buf: Uint8Array, len: number) {
+    const bl = buf.length;
+    if(len <= bl) return buf;
+    const nbuf = new Uint8Array(Math.max(bl << 1, len));
+    nbuf.set(buf, 0);
+    // for(var i=0; i<bl; i+=4) {  nbuf[i]=buf[i];  nbuf[i+1]=buf[i+1];  nbuf[i+2]=buf[i+2];  nbuf[i+3]=buf[i+3];  }
+    return nbuf;
+}
+
+function _decodeTiny(lmap: NumberArray, LL: number, len: number, data: Uint8Array, pos: number, tree: number[]) {
+    let i = 0;
+    while(i<len) {
+        const code = lmap[_get17(data, pos)&LL];
+        pos += code&15;
+        const lit = code>>>4;
+        if(lit<=15) {
+            tree[i]=lit;
+            i++;
+        } else {
+            let ll = 0, n = 0;
+            if(lit === 16) {
+                n = (3  + _bitsE(data, pos, 2));  pos += 2;  ll = tree[i-1];
+            } else if(lit === 17) {
+                n = (3  + _bitsE(data, pos, 3));  pos += 3;
+            } else if(lit === 18) {
+                n = (11 + _bitsE(data, pos, 7));  pos += 7;
+            }
+            const ni = i+n;
+            while(i<ni) {
+                tree[i]=ll;
+                i++;
+            }
+        }
+    }
+    return pos;
+}
+
+function _copyOut(src: number[], off: number, len: number, tree: number[]) {
+    let mx=0, i=0, tl=tree.length>>>1;
+    while(i<len) {
+        let v=src[i+off];
+        tree[(i<<1)]=0;
+        tree[(i<<1)+1]=v;
+        if(v>mx)mx=v;
+        i++;
+    }
+    while(i<tl ) {
+        tree[(i<<1)]=0;
+        tree[(i<<1)+1]=0;
+        i++;
+    }
+    return mx;
+}
+
+function _bitsE(dt: NumberArray, pos: number, length: number) {
+    return ((dt[pos>>>3] | (dt[(pos>>>3)+1]<<8))>>>(pos&7))&((1<<length)-1);
+}
+
+function _bitsF(dt: NumberArray, pos: number, length: number) {
+    return ((dt[pos>>>3] | (dt[(pos>>>3)+1]<<8) | (dt[(pos>>>3)+2]<<16))>>>(pos&7))&((1<<length)-1);
+}
+
+function _get17(dt: NumberArray, pos: number) {	// return at least 17 meaningful bytes
+    return (dt[pos>>>3] | (dt[(pos>>>3)+1]<<8) | (dt[(pos>>>3)+2]<<16) )>>>(pos&7);
+}
\ No newline at end of file

src/mol-util/zip/util.ts

+/**
+ * Copyright (c) 2020 mol* contributors, licensed under MIT, See LICENSE file for more info.
+ *
+ * @author Alexander Rose <alexander.rose@weirdbyte.de>
+ *
+ * ported from https://github.com/photopea/UZIP.js/blob/master/UZIP.js
+ * MIT License, Copyright (c) 2018 Photopea
+ */
+
+export const U = (function(){
+    const u16=Uint16Array, u32=Uint32Array;
+    return {
+        next_code : new u16(16),
+        bl_count  : new u16(16),
+        ordr : [ 16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15 ],
+        of0  : [3,4,5,6,7,8,9,10,11,13,15,17,19,23,27,31,35,43,51,59,67,83,99,115,131,163,195,227,258,999,999,999],
+        exb  : [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,  0,  0,  0],
+        ldef : new u16(32),
+        df0  : [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, 65535, 65535],
+        dxb  : [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,     0,     0],
+        ddef : new u32(32),
+        flmap: new u16(  512),  fltree: [] as number[],
+        fdmap: new u16(   32),  fdtree: [] as number[],
+        lmap : new u16(32768),  ltree : [] as number[],  ttree:[] as number[],
+        dmap : new u16(32768),  dtree : [] as number[],
+        imap : new u16(  512),  itree : [] as number[],
+        // rev9 : new u16(  512)
+        rev15: new u16(1<<15),
+        lhst : new u32(286), dhst : new u32( 30), ihst : new u32(19),
+        lits : new u32(15000),
+        strt : new u16(1<<16),
+        prev : new u16(1<<15)
+    };
+})();
+
+(function(){
+    const len = 1<<15;
+    for(let i=0; i<len; i++) {
+        let x = i;
+        x = (((x & 0xaaaaaaaa) >>> 1) | ((x & 0x55555555) << 1));
+        x = (((x & 0xcccccccc) >>> 2) | ((x & 0x33333333) << 2));
+        x = (((x & 0xf0f0f0f0) >>> 4) | ((x & 0x0f0f0f0f) << 4));
+        x = (((x & 0xff00ff00) >>> 8) | ((x & 0x00ff00ff) << 8));
+        U.rev15[i] = (((x >>> 16) | (x << 16)))>>>17;
+    }
+
+    function pushV(tgt: number[], n: number, sv: number) {
+        while(n-- !== 0) tgt.push(0, sv);
+    }
+
+    for(let i=0; i<32; i++) {
+        U.ldef[i] = (U.of0[i]<<3)|U.exb[i];
+        U.ddef[i] = (U.df0[i]<<4)|U.dxb[i];
+    }
+
+    pushV(U.fltree, 144, 8);
+    pushV(U.fltree, 255-143, 9);
+    pushV(U.fltree, 279-255, 7);
+    pushV(U.fltree,287-279,8);
+    /*
+    var i = 0;
+    for(; i<=143; i++) U.fltree.push(0,8);
+    for(; i<=255; i++) U.fltree.push(0,9);
+    for(; i<=279; i++) U.fltree.push(0,7);
+    for(; i<=287; i++) U.fltree.push(0,8);
+    */
+    makeCodes(U.fltree, 9);
+    codes2map(U.fltree, 9, U.flmap);
+    revCodes (U.fltree, 9)
+
+    pushV(U.fdtree,32,5);
+    // for(i=0;i<32; i++) U.fdtree.push(0,5);
+    makeCodes(U.fdtree, 5);
+    codes2map(U.fdtree, 5, U.fdmap);
+    revCodes (U.fdtree, 5)
+
+    pushV(U.itree,19,0);  pushV(U.ltree,286,0);  pushV(U.dtree,30,0);  pushV(U.ttree,320,0);
+    /*
+    for(var i=0; i< 19; i++) U.itree.push(0,0);
+    for(var i=0; i<286; i++) U.ltree.push(0,0);
+    for(var i=0; i< 30; i++) U.dtree.push(0,0);
+    for(var i=0; i<320; i++) U.ttree.push(0,0);
+    */
+})();
+
+export function codes2map(tree: number[], MAX_BITS: number, map: Uint16Array) {
+    const max_code = tree.length;
+    const r15 = U.rev15;
+    for(let i=0; i<max_code; i+=2) {
+        if(tree[i+1] !== 0)  {
+            const lit = i>>1;
+            const cl = tree[i+1], val = (lit<<4)|cl; // :  (0x8000 | (U.of0[lit-257]<<7) | (U.exb[lit-257]<<4) | cl);
+            const rest = (MAX_BITS-cl)
+            let i0 = tree[i]<<rest
+            const i1 = i0 + (1<<rest);
+            // tree[i]=r15[i0]>>>(15-MAX_BITS);
+            while(i0 !== i1) {
+                const p0 = r15[i0]>>>(15-MAX_BITS);
+                map[p0]=val;  i0++;
+            }
+        }
+    }
+}
+
+export function makeCodes(tree: number[], MAX_BITS: number) {  // code, length
+    const max_code = tree.length;
+
+    const bl_count = U.bl_count;
+    for(let i=0; i<=MAX_BITS; i++) bl_count[i]=0;
+    for(let i=1; i<max_code; i+=2) bl_count[tree[i]]++;
+
+    const next_code = U.next_code;	// smallest code for each length
+
+    let code = 0;
+    bl_count[0] = 0;
+    for (let bits = 1; bits <= MAX_BITS; bits++) {
+        code = (code + bl_count[bits-1]) << 1;
+        next_code[bits] = code;
+    }
+
+    for (let n = 0; n < max_code; n+=2) {
+        const len = tree[n+1];
+        if (len !== 0) {
+            tree[n] = next_code[len];
+            next_code[len]++;
+        }
+    }
+}
+
+export function revCodes(tree: number[], MAX_BITS: number) {
+    const r15 = U.rev15, imb = 15-MAX_BITS;
+    for(let i=0; i<tree.length; i+=2) {
+        const i0 = (tree[i]<<(MAX_BITS-tree[i+1]));
+        tree[i] = r15[i0]>>>imb;
+    }
+}
\ No newline at end of file

src/mol-util/zip/zip.ts

+/**
+ * Copyright (c) 2020 mol* contributors, licensed under MIT, See LICENSE file for more info.
+ *
+ * @author Alexander Rose <alexander.rose@weirdbyte.de>
+ *
+ * ported from https://github.com/photopea/UZIP.js/blob/master/UZIP.js
+ * MIT License, Copyright (c) 2018 Photopea
+ *
+ * - added `ungzip`
+ */
+
+import { writeUint, writeUshort, sizeUTF8, writeUTF8, readUshort, readUint, readUTF8, toInt32 } from './bin';
+import { crc, adler } from './checksum';
+import { _inflate } from './inflate';
+import { _deflateRaw } from './deflate';
+
+export function parse(buf: ArrayBuffer, onlyNames = false) {
+    const out: { [k: string]: Uint8Array | { size: number, csize: number } } = Object.create(null);
+    const data = new Uint8Array(buf);
+    let eocd = data.length-4;
+
+    while(readUint(data, eocd) !== 0x06054b50) eocd--;
+
+    let o = eocd;
+    o += 4;	// sign  = 0x06054b50
+    o += 4; // disks = 0;
+    const cnu = readUshort(data, o);
+    o += 2;
+    // const cnt = readUshort(data, o);
+    o += 2;
+
+    // const csize = readUint(data, o);
+    o+=4;
+    const coffs = readUint(data, o);  o+=4;
+
+    o = coffs;
+    for(let i = 0; i<cnu; i++) {
+        // const sign = readUint(data, o);
+        o += 4;
+        o += 4;  // versions;
+        o += 4;  // flag + compr
+        o += 4;  // time
+
+        // const crc32 = readUint(data, o);
+        o+=4;
+        const csize = readUint(data, o);
+        o+=4;
+        const usize = readUint(data, o);
+        o+=4;
+
+        const nl = readUshort(data, o)
+        const el = readUshort(data, o+2)
+        const cl = readUshort(data, o+4);
+        o += 6;  // name, extra, comment
+        o += 8;  // disk, attribs
+
+        const roff = readUint(data, o);  o+=4;
+        o += nl + el + cl;
+
+        _readLocal(data, roff, out, csize, usize, onlyNames);
+    }
+    // console.log(out);
+    return out;
+}
+
+function _readLocal(data: Uint8Array, o: number, out: { [k: string]: Uint8Array | { size: number, csize: number } }, csize: number, usize: number, onlyNames: boolean) {
+    // const sign  = readUint(data, o);
+    o+=4;
+    // const ver   = readUshort(data, o);
+    o+=2;
+    // const gpflg = readUshort(data, o);
+    o+=2;
+    // if((gpflg&8)!=0) throw "unknown sizes";
+    const cmpr  = readUshort(data, o);
+    o+=2;
+
+    // const time  = readUint(data, o);
+    o+=4;
+
+    // const crc32 = readUint(data, o);
+    o+=4;
+    // var csize = rUi(data, o);  o+=4;
+    // var usize = rUi(data, o);  o+=4;
+    o+=8;
+
+    const nlen  = readUshort(data, o);
+    o+=2;
+    const elen  = readUshort(data, o);
+    o+=2;
+
+    const name =  readUTF8(data, o, nlen);
+    o += nlen;  // console.log(name);
+    o += elen;
+
+    // console.log(sign.toString(16), ver, gpflg, cmpr, crc32.toString(16), "csize, usize", csize, usize, nlen, elen, name, o);
+    if(onlyNames) {
+        out[name] = { size: usize, csize };
+        return;
+    }
+
+    const file = new Uint8Array(data.buffer, o);
+    if(cmpr === 0) {
+        out[name] = new Uint8Array(file.buffer.slice(o, o+csize));
+    } else if(cmpr === 8) {
+        const buf = new Uint8Array(usize);
+        inflateRaw(file, buf);
+        // var nbuf = pako["inflateRaw"](file);
+        // if(usize>8514000) {
+        //     //console.log(PUtils.readASCII(buf , 8514500, 500));
+        //     //console.log(PUtils.readASCII(nbuf, 8514500, 500));
+        // }
+        // for(var i=0; i<buf.length; i++) if(buf[i]!=nbuf[i]) {  console.log(buf.length, nbuf.length, usize, i);  throw "e";  }
+        out[name] = buf;
+    }
+    else throw `unknown compression method: ${cmpr}`;
+}
+
+export function inflateRaw(file: Uint8Array, buf?: Uint8Array) {
+    return _inflate(file, buf);
+}
+
+export function inflate(file: Uint8Array, buf?: Uint8Array) {
+    // const CMF = file[0]
+    // const FLG = file[1]
+    // const CM = (CMF&15)
+    // const CINFO = (CMF>>>4);
+    // console.log(CM, CINFO,CMF,FLG);
+    return inflateRaw(new Uint8Array(file.buffer, file.byteOffset+2, file.length-6), buf);
+}
+
+// https://tools.ietf.org/html/rfc1952
+export function ungzip(file: Uint8Array, buf?: Uint8Array) {
+    // const id1 = file[0]
+    // const id2 = file[1]
+    // const cm = file[2]
+    const flg = file[3]
+    // const mtime = readUint(file, 4)
+    // const xfl = file[8]
+    // const os = file[9]
+
+    let o = 10
+    if (flg & 4) { // FEXTRA
+        const xlen = readUshort(file, o)
+        // console.log('FEXTRA', xlen)
+        o += xlen
+    }
+    if (flg & 8) { // FNAME
+        let zero = o
+        while(file[zero] !== 0) ++zero
+        // const name = readUTF8(file, o, zero - o)
+        // console.log('FNAME', name, zero - o)
+        o = zero + 1
+    }
+    if (flg & 16) { // FCOMMENT
+        let zero = o
+        while(file[zero] !== 0) ++zero
+        // const comment = readUTF8(file, o, zero - o)
+        // console.log('FCOMMENT', comment)
+        o = zero + 1
+    }
+
+    if (flg & 1) { // FHCRC
+        // const hcrc = readUshort(file, o)
+        // console.log('FHCRC', hcrc)
+        o += 2
+    }
+
+    const crc32 = toInt32(readUint(file, file.length - 8))
+    const isize = readUint(file, file.length - 4)
+    if (buf === undefined) buf = new Uint8Array(isize)
+
+    const blocks = new Uint8Array(file.buffer, file.byteOffset + o, file.length - o - 8)
+    const inflated = inflateRaw(blocks, buf);
+    const crcValue = crc(inflated, 0, inflated.length)
+    if (crc32 !== crcValue) {
+        console.error("ungzip: checksums don't match")
+    }
+
+    return inflated
+}
+
+export function deflate(data: Uint8Array, opts?: { level: number }/* , buf, off*/) {
+    if(opts === undefined) opts={ level: 6 };
+    let off=0
+    const buf = new Uint8Array(50 + Math.floor(data.length * 1.1));
+    buf[off]=120;  buf[off+1]=156;  off+=2;
+    off = _deflateRaw(data, buf, off, opts.level);
+    const crcValue = adler(data, 0, data.length);
+    buf[off+0] = ((crcValue>>>24)&255);
+    buf[off+1] = ((crcValue>>>16)&255);
+    buf[off+2] = ((crcValue>>> 8)&255);
+    buf[off+3] = ((crcValue>>> 0)&255);
+    return new Uint8Array(buf.buffer, 0, off+4);
+}
+
+function deflateRaw(data: Uint8Array, opts?: { level: number }) {
+    if(opts === undefined) opts = { level: 6 };
+    const buf = new Uint8Array(50 + Math.floor(data.length * 1.1));
+    const off = _deflateRaw(data, buf, 0, opts.level);
+    return new Uint8Array(buf.buffer, 0, off);
+}
+
+export function encode(obj: { [k: string]: Uint8Array }, noCmpr = false) {
+    let tot = 0;
+    const zpd: { [k: string]: { cpr: boolean, usize: number, crc: number, file: Uint8Array } } = {};
+    for(const p in obj) {
+        const cpr = !_noNeed(p) && !noCmpr, buf = obj[p]
+        const crcValue = crc(buf, 0, buf.length);
+        zpd[p] = {
+            cpr,
+            usize: buf.length,
+            crc: crcValue,
+            file: (cpr ? deflateRaw(buf) : buf)
+        };
+    }
+
+    for(const p in zpd) tot += zpd[p].file.length + 30 + 46 + 2 * sizeUTF8(p);
+    tot +=  22;
+
+    const data = new Uint8Array(tot)
+    let o = 0;
+    const fof = []
+
+    for(const p in zpd) {
+        const file = zpd[p];  fof.push(o);
+        o = _writeHeader(data, o, p, file, 0);
+    }
+    let i=0, ioff = o;
+    for(const p in zpd) {
+        const file = zpd[p];
+        fof.push(o);
+        o = _writeHeader(data, o, p, file, 1, fof[i++]);
+    }
+    const csize = o-ioff;
+
+    writeUint(data, o, 0x06054b50);  o+=4;
+    o += 4;  // disks
+    writeUshort(data, o, i);  o += 2;
+    writeUshort(data, o, i);  o += 2;	// number of c d records
+    writeUint(data, o, csize);  o += 4;
+    writeUint(data, o, ioff );  o += 4;
+    o += 2;
+    return data.buffer;
+}
+
+// no need to compress .PNG, .ZIP, .JPEG ....
+function _noNeed(fn: string) {
+    const ext = fn.split('.').pop()!.toLowerCase();
+    return 'png,jpg,jpeg,zip'.indexOf(ext) !== -1;
+}
+
+function _writeHeader(data: Uint8Array, o: number, p: string, obj: { cpr: boolean, usize: number, crc: number, file: Uint8Array }, t: number, roff = 0) {
+    const file = obj.file;
+
+    writeUint(data, o, t === 0 ? 0x04034b50 : 0x02014b50); o+=4; // sign
+    if(t === 1) o+=2;  // ver made by
+    writeUshort(data, o, 20);  o+=2;	// ver
+    writeUshort(data, o,  0);  o+=2;    // gflip
+    writeUshort(data, o,  obj.cpr?8:0);  o+=2;	// cmpr
+
+    writeUint(data, o,  0);  o+=4;	// time
+    writeUint(data, o, obj.crc);  o+=4;	// crc32
+    writeUint(data, o, file.length);  o+=4;	// csize
+    writeUint(data, o, obj.usize);  o+=4;	// usize
+
+    writeUshort(data, o, sizeUTF8(p));  o+=2;	// nlen
+    writeUshort(data, o, 0);  o+=2;	// elen
+
+    if(t === 1) {
+        o += 2;  // comment length
+        o += 2;  // disk number
+        o += 6;  // attributes
+        writeUint(data, o, roff);  o+=4;	// usize
+    }
+    const nlen = writeUTF8(data, o, p);  o+= nlen;
+    if(t === 0) {
+        data.set(file, o);
+        o += file.length;
+    }
+    return o;
+}
\ No newline at end of file