52 lines
1.4 KiB
TypeScript
52 lines
1.4 KiB
TypeScript
// Copyright 2024 Signal Messenger, LLC
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// SPDX-License-Identifier: AGPL-3.0-only
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import { Transform } from 'node:stream';
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import { strictAssert } from './assert';
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/**
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* Truncates the stream to the target size and analyzes padding type.
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*/
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export function trimPadding(
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size: number,
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onPaddingAnalyzed: ({
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isPaddingAllZeros,
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}: {
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isPaddingAllZeros: boolean;
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}) => void
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): Transform {
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let total = 0;
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let seenNonZeroPadding = false;
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return new Transform({
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transform(chunk, _encoding, callback) {
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strictAssert(chunk instanceof Uint8Array, 'chunk must be Uint8Array');
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const chunkSize = chunk.byteLength;
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const sizeLeft = size - total;
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let paddingInThisChunk: Uint8Array | undefined;
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if (sizeLeft >= chunkSize) {
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total += chunkSize;
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callback(null, chunk);
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} else if (sizeLeft > 0) {
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total += sizeLeft;
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const data = chunk.subarray(0, sizeLeft);
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paddingInThisChunk = chunk.subarray(sizeLeft);
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callback(null, data);
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} else {
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paddingInThisChunk = chunk;
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callback(null, null);
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}
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if (
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paddingInThisChunk &&
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!seenNonZeroPadding &&
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!paddingInThisChunk.every(el => el === 0)
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) {
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seenNonZeroPadding = true;
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}
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},
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flush(callback) {
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onPaddingAnalyzed({ isPaddingAllZeros: !seenNonZeroPadding });
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callback();
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},
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});
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}
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