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wasm-hash.js
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Wed, Feb 5, 18:11

wasm-hash.js
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/*
MIT License http://www.opensource.org/licenses/mit-license.php
Author Tobias Koppers @sokra
*/
"use strict";
// 65536 is the size of a wasm memory page
// 64 is the maximum chunk size for every possible wasm hash implementation
// 4 is the maximum number of bytes per char for string encoding (max is utf-8)
// ~3 makes sure that it's always a block of 4 chars, so avoid partially encoded bytes for base64
const MAX_SHORT_STRING = Math.floor((65536 - 64) / 4) & ~3;
class WasmHash {
/**
* @param {WebAssembly.Instance} instance wasm instance
* @param {WebAssembly.Instance[]} instancesPool pool of instances
* @param {number} chunkSize size of data chunks passed to wasm
* @param {number} digestSize size of digest returned by wasm
*/
constructor(instance, instancesPool, chunkSize, digestSize) {
const exports = /** @type {any} */ (instance.exports);
exports.init();
this.exports = exports;
this.mem = Buffer.from(exports.memory.buffer, 0, 65536);
this.buffered = 0;
this.instancesPool = instancesPool;
this.chunkSize = chunkSize;
this.digestSize = digestSize;
}
reset() {
this.buffered = 0;
this.exports.init();
}
/**
* @param {Buffer | string} data data
* @param {BufferEncoding=} encoding encoding
* @returns {this} itself
*/
update(data, encoding) {
if (typeof data === "string") {
while (data.length > MAX_SHORT_STRING) {
this._updateWithShortString(data.slice(0, MAX_SHORT_STRING), encoding);
data = data.slice(MAX_SHORT_STRING);
}
this._updateWithShortString(data, encoding);
return this;
}
this._updateWithBuffer(data);
return this;
}
/**
* @param {string} data data
* @param {BufferEncoding=} encoding encoding
* @returns {void}
*/
_updateWithShortString(data, encoding) {
const { exports, buffered, mem, chunkSize } = this;
let endPos;
if (data.length < 70) {
if (!encoding || encoding === "utf-8" || encoding === "utf8") {
endPos = buffered;
for (let i = 0; i < data.length; i++) {
const cc = data.charCodeAt(i);
if (cc < 0x80) {
mem[endPos++] = cc;
} else if (cc < 0x800) {
mem[endPos] = (cc >> 6) | 0xc0;
mem[endPos + 1] = (cc & 0x3f) | 0x80;
endPos += 2;
} else {
// bail-out for weird chars
endPos += mem.write(data.slice(i), endPos, encoding);
break;
}
}
} else if (encoding === "latin1") {
endPos = buffered;
for (let i = 0; i < data.length; i++) {
const cc = data.charCodeAt(i);
mem[endPos++] = cc;
}
} else {
endPos = buffered + mem.write(data, buffered, encoding);
}
} else {
endPos = buffered + mem.write(data, buffered, encoding);
}
if (endPos < chunkSize) {
this.buffered = endPos;
} else {
const l = endPos & ~(this.chunkSize - 1);
exports.update(l);
const newBuffered = endPos - l;
this.buffered = newBuffered;
if (newBuffered > 0) {
mem.copyWithin(0, l, endPos);
}
}
}
/**
* @param {Buffer} data data
* @returns {void}
*/
_updateWithBuffer(data) {
const { exports, buffered, mem } = this;
const length = data.length;
if (buffered + length < this.chunkSize) {
data.copy(mem, buffered, 0, length);
this.buffered += length;
} else {
const l = (buffered + length) & ~(this.chunkSize - 1);
if (l > 65536) {
let i = 65536 - buffered;
data.copy(mem, buffered, 0, i);
exports.update(65536);
const stop = l - buffered - 65536;
while (i < stop) {
data.copy(mem, 0, i, i + 65536);
exports.update(65536);
i += 65536;
}
data.copy(mem, 0, i, l - buffered);
exports.update(l - buffered - i);
} else {
data.copy(mem, buffered, 0, l - buffered);
exports.update(l);
}
const newBuffered = length + buffered - l;
this.buffered = newBuffered;
if (newBuffered > 0) {
data.copy(mem, 0, length - newBuffered, length);
}
}
}
digest(type) {
const { exports, buffered, mem, digestSize } = this;
exports.final(buffered);
this.instancesPool.push(this);
const hex = mem.toString("latin1", 0, digestSize);
if (type === "hex") {
return hex;
}
if (type === "binary" || !type) {
return Buffer.from(hex, "hex");
}
return Buffer.from(hex, "hex").toString(type);
}
}
const create = (wasmModule, instancesPool, chunkSize, digestSize) => {
if (instancesPool.length > 0) {
const old = instancesPool.pop();
old.reset();
return old;
} else {
return new WasmHash(
new WebAssembly.Instance(wasmModule),
instancesPool,
chunkSize,
digestSize
);
}
};
module.exports = create;
module.exports.MAX_SHORT_STRING = MAX_SHORT_STRING;

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