85 lines
3.2 KiB
JavaScript
85 lines
3.2 KiB
JavaScript
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import {getStreamContents} from './contents.js';
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import {noop, throwObjectStream, getLengthProp} from './utils.js';
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export async function getStreamAsArrayBuffer(stream, options) {
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return getStreamContents(stream, arrayBufferMethods, options);
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}
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const initArrayBuffer = () => ({contents: new ArrayBuffer(0)});
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const useTextEncoder = chunk => textEncoder.encode(chunk);
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const textEncoder = new TextEncoder();
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const useUint8Array = chunk => new Uint8Array(chunk);
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const useUint8ArrayWithOffset = chunk => new Uint8Array(chunk.buffer, chunk.byteOffset, chunk.byteLength);
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const truncateArrayBufferChunk = (convertedChunk, chunkSize) => convertedChunk.slice(0, chunkSize);
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// `contents` is an increasingly growing `Uint8Array`.
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const addArrayBufferChunk = (convertedChunk, {contents, length: previousLength}, length) => {
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const newContents = hasArrayBufferResize() ? resizeArrayBuffer(contents, length) : resizeArrayBufferSlow(contents, length);
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new Uint8Array(newContents).set(convertedChunk, previousLength);
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return newContents;
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};
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// Without `ArrayBuffer.resize()`, `contents` size is always a power of 2.
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// This means its last bytes are zeroes (not stream data), which need to be
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// trimmed at the end with `ArrayBuffer.slice()`.
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const resizeArrayBufferSlow = (contents, length) => {
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if (length <= contents.byteLength) {
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return contents;
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}
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const arrayBuffer = new ArrayBuffer(getNewContentsLength(length));
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new Uint8Array(arrayBuffer).set(new Uint8Array(contents), 0);
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return arrayBuffer;
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};
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// With `ArrayBuffer.resize()`, `contents` size matches exactly the size of
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// the stream data. It does not include extraneous zeroes to trim at the end.
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// The underlying `ArrayBuffer` does allocate a number of bytes that is a power
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// of 2, but those bytes are only visible after calling `ArrayBuffer.resize()`.
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const resizeArrayBuffer = (contents, length) => {
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if (length <= contents.maxByteLength) {
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contents.resize(length);
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return contents;
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}
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const arrayBuffer = new ArrayBuffer(length, {maxByteLength: getNewContentsLength(length)});
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new Uint8Array(arrayBuffer).set(new Uint8Array(contents), 0);
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return arrayBuffer;
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};
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// Retrieve the closest `length` that is both >= and a power of 2
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const getNewContentsLength = length => SCALE_FACTOR ** Math.ceil(Math.log(length) / Math.log(SCALE_FACTOR));
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const SCALE_FACTOR = 2;
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const finalizeArrayBuffer = ({contents, length}) => hasArrayBufferResize() ? contents : contents.slice(0, length);
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// `ArrayBuffer.slice()` is slow. When `ArrayBuffer.resize()` is available
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// (Node >=20.0.0, Safari >=16.4 and Chrome), we can use it instead.
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// eslint-disable-next-line no-warning-comments
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// TODO: remove after dropping support for Node 20.
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// eslint-disable-next-line no-warning-comments
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// TODO: use `ArrayBuffer.transferToFixedLength()` instead once it is available
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const hasArrayBufferResize = () => 'resize' in ArrayBuffer.prototype;
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const arrayBufferMethods = {
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init: initArrayBuffer,
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convertChunk: {
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string: useTextEncoder,
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buffer: useUint8Array,
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arrayBuffer: useUint8Array,
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dataView: useUint8ArrayWithOffset,
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typedArray: useUint8ArrayWithOffset,
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others: throwObjectStream,
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},
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getSize: getLengthProp,
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truncateChunk: truncateArrayBufferChunk,
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addChunk: addArrayBufferChunk,
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getFinalChunk: noop,
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finalize: finalizeArrayBuffer,
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};
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