packages/wasm-util/src/fflate.ts
// Copyright 2019-2024 @polkadot/wasm-util authors & contributors
// SPDX-License-Identifier: Apache-2.0
// MIT License
//
// Copyright (c) 2020 Arjun Barrett
//
// Copied from https://github.com/101arrowz/fflate/blob/73c737941ec89d85cdf0ad39ee6f26c5fdc95fd7/src/index.ts
// This only contains the unzlibSync function, no compression, no async, no workers
//
// These 2 issues are addressed as a short-term, stop-gap solution
// - https://github.com/polkadot-js/api/issues/2963
// - https://github.com/101arrowz/fflate/issues/17
//
// Only tweaks made here are some TS adjustments (we use strict null checks),
// the code is otherwise as-is with only the single required function provided
// (compression is still being done in the build with fflate)
/* eslint-disable */
// inflate state
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;
};
// aliases for shorter compressed code (most minifers don't do this)
const u8 = Uint8Array, u16 = Uint16Array, u32 = Uint32Array;
// code length index map
const clim = new u8([16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15]);
// fixed length extra bits
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]);
// fixed distance extra bits
// see fleb note
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]);
// get base, reverse index map from extra bits
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);
// we can ignore the fact that the other numbers are wrong; they never happen anyway
fl[28] = 258, revfl[258] = 28;
const [fd] = freb(fdeb, 0);
// map of value to reverse (assuming 16 bits)
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;
}
// create huffman tree from u8 "map": index -> code length for code index
// mb (max bits) must be at most 15
// TODO: optimize/split up?
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) {
if (cd[i]) ++l[cd[i] - 1];
}
// u16 "map": index -> minimum code for bit length = index
const le = new u16(mb);
for (i = 1; 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) {
if (cd[i]) {
co[i] = rev[le[cd[i] - 1]++] >> (15 - cd[i]);
}
}
}
return co;
});
// fixed length tree
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;
// fixed distance tree
const fdt = new u8(32);
for (let i = 0; i < 32; ++i) fdt[i] = 5;
// fixed length map
const flrm = hMap(flt, 9, 1);
// fixed distance map
const fdrm = hMap(fdt, 5, 1);
// read d, starting at bit p and mask with m
const bits = (d: Uint8Array, p: number, m: number) => {
const o = p >>> 3;
return ((d[o] | (d[o + 1] << 8)) >>> (p & 7)) & m;
}
// read d, starting at bit p continuing for at least 16 bits
const bits16 = (d: Uint8Array, p: number) => {
const o = p >>> 3;
return ((d[o] | (d[o + 1] << 8) | (d[o + 2] << 16)) >>> (p & 7));
}
// get end of byte
const shft = (p: number) => (p >>> 3) + (p & 7 && 1);
// typed array slice - allows garbage collector to free original reference,
// while being more compatible than .slice
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;
}
// find max of array
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;
};
// expands raw DEFLATE data
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);
}
// zlib valid
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);
}