fflate.ts

/* eslint-disable */

type InflateState = {
  // lmap
  l?: Uint16Array | undefined;
  // dmap
  d?: Uint16Array | undefined;
  // lbits
  m?: number | undefined;
  // dbits
  n?: number | undefined;
  // final
  f?: number;
  // pos
  p?: number;
  // byte
  b?: number;
  // lstchk
  i?: boolean;
};

const u8 = Uint8Array, u16 = Uint16Array, u32 = Uint32Array;

const clim = new u8([16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15]);

const fleb = new u8([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, /* unused */ 0, 0, /* impossible */ 0]);

const fdeb = new u8([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, /* unused */ 0, 0]);

const freb = (eb: Uint8Array, start: number) => {
  const b = new u16(31);
  for (let i = 0; i < 31; ++i) {
    b[i] = start += 1 << eb[i - 1];
  }
  // numbers here are at max 18 bits
  const r = new u32(b[30]);
  for (let i = 1; i < 30; ++i) {
    for (let j = b[i]; j < b[i + 1]; ++j) {
      r[j] = ((j - b[i]) << 5) | i;
    }
  }
  return [b, r] as const;
}

const [fl, revfl] = freb(fleb, 2);
fl[28] = 258, revfl[258] = 28;
const [fd] = freb(fdeb, 0);

const rev = new u16(32768);
for (let i = 0; i < 32768; ++i) {
  // reverse table algorithm from SO
  let x = ((i & 0xAAAA) >>> 1) | ((i & 0x5555) << 1);
  x = ((x & 0xCCCC) >>> 2) | ((x & 0x3333) << 2);
  x = ((x & 0xF0F0) >>> 4) | ((x & 0x0F0F) << 4);
  rev[i] = (((x & 0xFF00) >>> 8) | ((x & 0x00FF) << 8)) >>> 1;
}

const hMap = ((cd: Uint8Array, mb: number, r: 0 | 1) => {
  const s = cd.length;
  // index
  let i = 0;
  // u16 "map": index -> # of codes with bit length = index
  const l = new u16(mb);
  // length of cd must be 288 (total # of codes)
  for (; i < s; ++i) ++l[cd[i] - 1];
  // u16 "map": index -> minimum code for bit length = index
  const le = new u16(mb);
  for (i = 0; i < mb; ++i) {
    le[i] = (le[i - 1] + l[i - 1]) << 1;
  }
  let co: Uint16Array;
  if (r) {
    // u16 "map": index -> number of actual bits, symbol for code
    co = new u16(1 << mb);
    // bits to remove for reverser
    const rvb = 15 - mb;
    for (i = 0; i < s; ++i) {
      // ignore 0 lengths
      if (cd[i]) {
        // num encoding both symbol and bits read
        const sv = (i << 4) | cd[i];
        // free bits
        const r = mb - cd[i];
        // start value
        let v = le[cd[i] - 1]++ << r;
        // m is end value
        for (const m = v | ((1 << r) - 1); v <= m; ++v) {
          // every 16 bit value starting with the code yields the same result
          co[rev[v] >>> rvb] = sv;
        }
      }
    }
  } else {
    co = new u16(s);
    for (i = 0; i < s; ++i) co[i] = rev[le[cd[i] - 1]++] >>> (15 - cd[i]);
  }
  return co;
});

const flt = new u8(288);
for (let i = 0; i < 144; ++i) flt[i] = 8;
for (let i = 144; i < 256; ++i) flt[i] = 9;
for (let i = 256; i < 280; ++i) flt[i] = 7;
for (let i = 280; i < 288; ++i) flt[i] = 8;
const fdt = new u8(32);
for (let i = 0; i < 32; ++i) fdt[i] = 5;

const flrm = hMap(flt, 9, 1);
const fdrm = hMap(fdt, 5, 1);

const bits = (d: Uint8Array, p: number, m: number) => {
  const o = p >>> 3;
  return ((d[o] | (d[o + 1] << 8)) >>> (p & 7)) & m;
}

const bits16 = (d: Uint8Array, p: number) => {
  const o = p >>> 3;
  return ((d[o] | (d[o + 1] << 8) | (d[o + 2] << 16)) >>> (p & 7));
}

const shft = (p: number) => (p >>> 3) + (p & 7 && 1);

const slc = <T extends Uint8Array | Uint16Array | Uint32Array>(v: T, s: number, e?: number): T => {
  if (s == null || s < 0) s = 0;
  if (e == null || e > v.length) e = v.length;
  // can't use .constructor in case user-supplied
  const n = new (v instanceof u16 ? u16 : v instanceof u32 ? u32 : u8)(e - s) as T;
  n.set(v.subarray(s, e));
  return n;
}

const max = (a: Uint8Array | number[]) => {
  let m = a[0];
  for (let i = 1, count = a.length; i < count; ++i) {
    if (a[i] > m) m = a[i];
  }
  return m;
};

const inflt = (dat: Uint8Array, buf?: Uint8Array, st?: InflateState) => {
  const noSt = !st || st.i;
  if (!st) st = {};
  // source length
  const sl = dat.length;
  // have to estimate size
  const noBuf = !buf || !noSt;
  // Assumes roughly 33% compression ratio average
  if (!buf) buf = new u8(sl * 3);
  // ensure buffer can fit at least l elements
  const cbuf = (l: number) => {
    let bl = buf!.length;
    // need to increase size to fit
    if (l > bl) {
      // Double or set to necessary, whichever is greater
      const nbuf = new u8(Math.max(bl << 1, l));
      nbuf.set(buf!);
      buf = nbuf;
    }
  };
  //  last chunk         bitpos           bytes
  let final = st.f || 0, pos = st.p || 0, bt = st.b || 0, lm = st.l, dm = st.d, lbt = st.m, dbt = st.n;
  if (final && !lm) return buf;
  // total bits
  const tbts = sl << 3;
  do {
    if (!lm) {
      // BFINAL - this is only 1 when last chunk is next
      st.f = final = bits(dat, pos, 1);
      // type: 0 = no compression, 1 = fixed huffman, 2 = dynamic huffman
      const type = bits(dat, pos + 1, 3);
      pos += 3;
      if (!type) {
        // go to end of byte boundary
        const s = shft(pos) + 4, l = dat[s - 4] | (dat[s - 3] << 8), t = s + l;
        if (t > sl) {
          if (noSt) throw 'unexpected EOF';
          break;
        }
        // ensure size
        if (noBuf) cbuf(bt + l);
        // Copy over uncompressed data
        buf.set(dat.subarray(s, t), bt);
        // Get new bitpos, update byte count
        st.b = bt += l, st.p = pos = t << 3;
        continue;
      }
      else if (type == 1) lm = flrm, dm = fdrm, lbt = 9, dbt = 5;
      else if (type == 2) {
        //  literal                            lengths
        const hLit = bits(dat, pos, 31) + 257, hcLen = bits(dat, pos + 10, 15) + 4;
        const tl = hLit + bits(dat, pos + 5, 31) + 1;
        pos += 14;
        // length+distance tree
        const ldt = new u8(tl);
        // code length tree
        const clt = new u8(19);
        for (let i = 0; i < hcLen; ++i) {
          // use index map to get real code
          clt[clim[i]] = bits(dat, pos + i * 3, 7);
        }
        pos += hcLen * 3;
        // code lengths bits
        const clb = max(clt), clbmsk = (1 << clb) - 1;
        if (!noSt && pos + tl * (clb + 7) > tbts) break;
        // code lengths map
        const clm = hMap(clt, clb, 1);
        for (let i = 0; i < tl;) {
          const r = clm[bits(dat, pos, clbmsk)];
          // bits read
          pos += r & 15;
          // symbol
          const s = r >>> 4;
          // code length to copy
          if (s < 16) {
            ldt[i++] = s;
          } else {
            //  copy   count
            let c = 0, n = 0;
            if (s == 16) n = 3 + bits(dat, pos, 3), pos += 2, c = ldt[i - 1];
            else if (s == 17) n = 3 + bits(dat, pos, 7), pos += 3;
            else if (s == 18) n = 11 + bits(dat, pos, 127), pos += 7;
            while (n--) ldt[i++] = c;
          }
        }
        //    length tree                 distance tree
        const lt = ldt.subarray(0, hLit), dt = ldt.subarray(hLit);
        // max length bits
        lbt = max(lt);
        // max dist bits
        dbt = max(dt);
        lm = hMap(lt, lbt, 1);
        dm = hMap(dt, dbt, 1);
      } else throw 'invalid block type';
      if (pos > tbts) throw 'unexpected EOF';
    }
    // Make sure the buffer can hold this + the largest possible addition
    // maximum chunk size (practically, theoretically infinite) is 2^17;
    if (noBuf) cbuf(bt + 131072);
    const lms = (1 << lbt!) - 1, dms = (1 << dbt!) - 1;
    const mxa = lbt! + dbt! + 18;
    while (noSt || pos + mxa < tbts) {
      // bits read, code
      const c = lm[bits16(dat, pos) & lms], sym = c >>> 4;
      pos += c & 15;
      if (pos > tbts) throw 'unexpected EOF';
      if (!c) throw 'invalid length/literal';
      if (sym < 256) buf[bt++] = sym;
      else if (sym == 256) {
        lm = undefined;
        break;
      }
      else {
        let add = sym - 254;
        // no extra bits needed if less
        if (sym > 264) {
          // index
          const i = sym - 257, b = fleb[i];
          add = bits(dat, pos, (1 << b) - 1) + fl[i];
          pos += b;
        }
        // dist
        const d = dm![bits16(dat, pos) & dms], dsym = d >>> 4;
        if (!d) throw 'invalid distance';
        pos += d & 15;
        let dt = fd[dsym];
        if (dsym > 3) {
          const b = fdeb[dsym];
          dt += bits16(dat, pos) & ((1 << b) - 1), pos += b;
        }
        if (pos > tbts) throw 'unexpected EOF';
        if (noBuf) cbuf(bt + 131072);
        const end = bt + add;
        for (; bt < end; bt += 4) {
          buf[bt] = buf[bt - dt];
          buf[bt + 1] = buf[bt + 1 - dt];
          buf[bt + 2] = buf[bt + 2 - dt];
          buf[bt + 3] = buf[bt + 3 - dt];
        }
        bt = end;
      }
    }
    st.l = lm, st.p = pos, st.b = bt;
    if (lm) final = 1, st.m = lbt, st.d = dm, st.n = dbt;
  } while (!final);
  return bt == buf.length ? buf : slc(buf, 0, bt);
}

const zlv = (d: Uint8Array) => {
  if ((d[0] & 15) != 8 || (d[0] >>> 4) > 7 || ((d[0] << 8 | d[1]) % 31)) throw 'invalid zlib data';
  if (d[1] & 32) throw 'invalid zlib data: preset dictionaries not supported';
}

/**
 * Expands Zlib data
 * @param data The data to decompress
 * @param out Where to write the data. Saves memory if you know the decompressed size and provide an output buffer of that length.
 * @returns The decompressed version of the data
 */
export function unzlibSync(data: Uint8Array, out?: Uint8Array) {
  return inflt((zlv(data), data.subarray(2, -4)), out);
}