91 lines
2.2 KiB
TypeScript
91 lines
2.2 KiB
TypeScript
// Copyright 2023 Signal Messenger, LLC
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// SPDX-License-Identifier: AGPL-3.0-only
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import { Transform } from 'stream';
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import { missingCaseError } from './missingCaseError';
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enum State {
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Prefix = 'Prefix',
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Data = 'Data',
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}
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export class DelimitedStream extends Transform {
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#state = State.Prefix;
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#prefixValue = 0;
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#prefixSize = 0;
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#parts = new Array<Buffer>();
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constructor() {
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super({ readableObjectMode: true });
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}
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override _transform(
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chunk: Buffer,
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_encoding: BufferEncoding,
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done: (error?: Error) => void
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): void {
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let offset = 0;
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while (offset < chunk.length) {
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if (this.#state === State.Prefix) {
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const b = chunk[offset];
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offset += 1;
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// See: https://protobuf.dev/programming-guides/encoding/
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// eslint-disable-next-line no-bitwise
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const isLast = (b & 0x80) === 0;
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// eslint-disable-next-line no-bitwise
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const value = b & 0x7f;
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// eslint-disable-next-line no-bitwise
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this.#prefixValue |= value << (7 * this.#prefixSize);
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this.#prefixSize += 1;
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// Check that we didn't go over 32bits. Node.js buffers can never
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// be larger than 2gb anyway!
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if (this.#prefixSize > 4) {
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done(new Error('Delimiter encoding overflow'));
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return;
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}
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if (isLast) {
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this.#state = State.Data;
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}
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} else if (this.#state === State.Data) {
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const toTake = Math.min(this.#prefixValue, chunk.length - offset);
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const part = chunk.slice(offset, offset + toTake);
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offset += toTake;
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this.#prefixValue -= toTake;
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this.#parts.push(part);
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if (this.#prefixValue <= 0) {
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this.#state = State.Prefix;
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this.#prefixSize = 0;
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this.#prefixValue = 0;
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const whole = Buffer.concat(this.#parts);
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this.#parts = [];
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this.push(whole);
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}
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} else {
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throw missingCaseError(this.#state);
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}
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}
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done();
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}
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override _flush(done: (error?: Error) => void): void {
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if (this.#state !== State.Prefix) {
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done(new Error('Unfinished data'));
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return;
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}
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if (this.#prefixSize !== 0) {
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done(new Error('Unfinished prefix'));
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return;
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}
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done();
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}
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}
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