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stream: implement TextEncoderStream and TextDecoderStream
Experimental as part of the web streams implementation Signed-off-by: James M Snell <[email protected]> PR-URL: #39347 Reviewed-By: Antoine du Hamel <[email protected]> Reviewed-By: Matteo Collina <[email protected]>
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‎doc/api/webstreams.md

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* `chunk` {any}
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* Returns: {number}
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### Class: `TextEncoderStream`
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<!-- YAML
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added: REPLACEME
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-->
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#### `new TextEncoderStream()`
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<!-- YAML
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added: REPLACEME
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-->
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Creates a new `TextEncoderStream` instance.
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#### `textEncoderStream.encoding`
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<!-- YAML
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added: REPLACEME
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-->
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* Type: {string}
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The encoding supported by the `TextEncoderStream` instance.
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#### `textEncoderStream.readable`
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<!-- YAML
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added: REPLACEME
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-->
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* Type: {ReadableStream}
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#### `textEncoderStream.writable`
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<!-- YAML
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added: REPLACEME
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-->
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* Type: {WritableStream}
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### Class: `TextDecoderStream`
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<!-- YAML
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added: REPLACEME
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-->
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#### `new TextDecoderStream([encoding[, options]])`
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<!-- YAML
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added: REPLACEME
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-->
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* `encoding` {string} Identifies the `encoding` that this `TextDecoder` instance
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supports. **Default:** `'utf-8'`.
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* `options` {Object}
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* `fatal` {boolean} `true` if decoding failures are fatal.
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* `ignoreBOM` {boolean} When `true`, the `TextDecoderStream` will include the
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byte order mark in the decoded result. When `false`, the byte order mark
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will be removed from the output. This option is only used when `encoding` is
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`'utf-8'`, `'utf-16be'` or `'utf-16le'`. **Default:** `false`.
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Creates a new `TextDecoderStream` instance.
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#### `textDecoderStream.encoding`
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<!-- YAML
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added: REPLACEME
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-->
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* Type: {string}
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The encoding supported by the `TextDecoderStream` instance.
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#### `textDecoderStream.fatal`
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<!-- YAML
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added: REPLACEME
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-->
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* Type: {boolean}
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The value will be `true` if decoding errors result in a `TypeError` being
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thrown.
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#### `textDecoderStream.ignoreBOM`
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<!-- YAML
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added: REPLACEME
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-->
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* Type: {boolean}
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The value will be `true` if the decoding result will include the byte order
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mark.
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#### `textDecoderStream.readable`
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<!-- YAML
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added: REPLACEME
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-->
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* Type: {ReadableStream}
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#### `textDecoderStream.writable`
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<!-- YAML
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added: REPLACEME
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-->
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* Type: {WritableStream}
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[Streams]: stream.md
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[WHATWG Streams Standard]: https://streams.spec.whatwg.org/

‎lib/internal/webstreams/encoding.js

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'use strict';
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const {
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ObjectDefineProperties,
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Symbol,
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} = primordials;
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const {
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TextDecoder,
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TextEncoder,
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} = require('internal/encoding');
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const {
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TransformStream,
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} = require('internal/webstreams/transformstream');
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const {
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customInspect,
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kEnumerableProperty,
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} = require('internal/webstreams/util');
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const {
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codes: {
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ERR_INVALID_THIS,
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},
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} = require('internal/errors');
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const {
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customInspectSymbol: kInspect
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} = require('internal/util');
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const kHandle = Symbol('kHandle');
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const kTransform = Symbol('kTransform');
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const kType = Symbol('kType');
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/**
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* @typedef {import('./readablestream').ReadableStream} ReadableStream
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* @typedef {import('./writablestream').WritableStream} WritableStream
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*/
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function isTextEncoderStream(value) {
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return typeof value?.[kHandle] === 'object' &&
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value?.[kType] === 'TextEncoderStream';
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}
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function isTextDecoderStream(value) {
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return typeof value?.[kHandle] === 'object' &&
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value?.[kType] === 'TextDecoderStream';
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}
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class TextEncoderStream {
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constructor() {
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this[kType] = 'TextEncoderStream';
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this[kHandle] = new TextEncoder();
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this[kTransform] = new TransformStream({
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transform: (chunk, controller) => {
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const value = this[kHandle].encode(chunk);
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if (value)
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controller.enqueue(value);
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},
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flush: (controller) => {
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const value = this[kHandle].encode();
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if (value.byteLength > 0)
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controller.enqueue(value);
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controller.terminate();
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},
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});
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}
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/**
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* @readonly
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* @type {string}
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*/
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get encoding() {
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if (!isTextEncoderStream(this))
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throw new ERR_INVALID_THIS('TextEncoderStream');
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return this[kHandle].encoding;
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}
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/**
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* @readonly
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* @type {ReadableStream}
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*/
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get readable() {
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if (!isTextEncoderStream(this))
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throw new ERR_INVALID_THIS('TextEncoderStream');
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return this[kTransform].readable;
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}
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/**
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* @readonly
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* @type {WritableStream}
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*/
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get writable() {
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if (!isTextEncoderStream(this))
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throw new ERR_INVALID_THIS('TextEncoderStream');
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return this[kTransform].writable;
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}
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[kInspect](depth, options) {
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if (!isTextEncoderStream(this))
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throw new ERR_INVALID_THIS('TextEncoderStream');
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return customInspect(depth, options, 'TextEncoderStream', {
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encoding: this[kHandle].encoding,
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readable: this[kTransform].readable,
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writable: this[kTransform].writable,
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});
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}
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}
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class TextDecoderStream {
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/**
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* @param {string} [encoding]
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* @param {{
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* fatal? : boolean,
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* ignoreBOM? : boolean,
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* }} [options]
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*/
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constructor(encoding = 'utf-8', options = {}) {
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this[kType] = 'TextDecoderStream';
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this[kHandle] = new TextDecoder(encoding, options);
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this[kTransform] = new TransformStream({
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transform: (chunk, controller) => {
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const value = this[kHandle].decode(chunk, { stream: true });
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if (value)
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controller.enqueue(value);
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},
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flush: (controller) => {
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const value = this[kHandle].decode();
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if (value)
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controller.enqueue(value);
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controller.terminate();
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},
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});
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}
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/**
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* @readonly
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* @type {string}
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*/
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get encoding() {
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if (!isTextDecoderStream(this))
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throw new ERR_INVALID_THIS('TextDecoderStream');
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return this[kHandle].encoding;
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}
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/**
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* @readonly
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* @type {boolean}
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*/
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get fatal() {
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if (!isTextDecoderStream(this))
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throw new ERR_INVALID_THIS('TextDecoderStream');
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return this[kHandle].fatal;
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}
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/**
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* @readonly
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* @type {boolean}
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*/
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get ignoreBOM() {
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if (!isTextDecoderStream(this))
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throw new ERR_INVALID_THIS('TextDecoderStream');
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return this[kHandle].ignoreBOM;
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}
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/**
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* @readonly
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* @type {ReadableStream}
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*/
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get readable() {
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if (!isTextDecoderStream(this))
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throw new ERR_INVALID_THIS('TextDecoderStream');
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return this[kTransform].readable;
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}
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/**
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* @readonly
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* @type {WritableStream}
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*/
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get writable() {
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if (!isTextDecoderStream(this))
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throw new ERR_INVALID_THIS('TextDecoderStream');
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return this[kTransform].writable;
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}
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[kInspect](depth, options) {
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if (!isTextDecoderStream(this))
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throw new ERR_INVALID_THIS('TextDecoderStream');
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return customInspect(depth, options, 'TextDecoderStream', {
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encoding: this[kHandle].encoding,
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fatal: this[kHandle].fatal,
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ignoreBOM: this[kHandle].ignoreBOM,
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readable: this[kTransform].readable,
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writable: this[kTransform].writable,
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});
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}
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}
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ObjectDefineProperties(TextEncoderStream.prototype, {
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encoding: kEnumerableProperty,
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readable: kEnumerableProperty,
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writable: kEnumerableProperty,
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});
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ObjectDefineProperties(TextDecoderStream.prototype, {
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encoding: kEnumerableProperty,
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fatal: kEnumerableProperty,
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ignoreBOM: kEnumerableProperty,
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readable: kEnumerableProperty,
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writable: kEnumerableProperty,
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});
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module.exports = {
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TextEncoderStream,
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TextDecoderStream,
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};

‎lib/stream/web.js

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CountQueuingStrategy,
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} = require('internal/webstreams/queuingstrategies');
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const {
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TextEncoderStream,
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TextDecoderStream,
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} = require('internal/webstreams/encoding');
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module.exports = {
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ReadableStream,
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ReadableStreamDefaultReader,
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WritableStreamDefaultController,
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ByteLengthQueuingStrategy,
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CountQueuingStrategy,
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TextEncoderStream,
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TextDecoderStream,
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};

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