2022-03-18 00:21:16 +01:00
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export function readableStreamTee<T = any>(
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readable: ReadableStream<T>
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): [ReadableStream<T>, ReadableStream<T>] {
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const transformStream = new TransformStream()
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const transformStream2 = new TransformStream()
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const writer = transformStream.writable.getWriter()
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const writer2 = transformStream2.writable.getWriter()
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const reader = readable.getReader()
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function read() {
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reader.read().then(({ done, value }) => {
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if (done) {
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writer.close()
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writer2.close()
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return
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}
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writer.write(value)
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writer2.write(value)
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read()
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})
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}
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read()
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return [transformStream.readable, transformStream2.readable]
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}
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export function chainStreams<T>(
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streams: ReadableStream<T>[]
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): ReadableStream<T> {
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const { readable, writable } = new TransformStream()
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let promise = Promise.resolve()
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for (let i = 0; i < streams.length; ++i) {
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promise = promise.then(() =>
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streams[i].pipeTo(writable, { preventClose: i + 1 < streams.length })
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2022-03-18 00:21:16 +01:00
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)
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}
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return readable
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}
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export function streamFromArray(strings: string[]): ReadableStream<Uint8Array> {
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// Note: we use a TransformStream here instead of instantiating a ReadableStream
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// because the built-in ReadableStream polyfill runs strings through TextEncoder.
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const { readable, writable } = new TransformStream()
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const writer = writable.getWriter()
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strings.forEach((str) => writer.write(encodeText(str)))
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writer.close()
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return readable
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}
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export async function streamToString(
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stream: ReadableStream<Uint8Array>
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): Promise<string> {
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const reader = stream.getReader()
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2022-04-06 15:34:24 +02:00
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const textDecoder = new TextDecoder()
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2022-03-18 00:21:16 +01:00
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let bufferedString = ''
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while (true) {
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const { done, value } = await reader.read()
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if (done) {
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return bufferedString
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}
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2022-04-06 15:34:24 +02:00
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bufferedString += decodeText(value, textDecoder)
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2022-03-18 00:21:16 +01:00
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}
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}
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export function encodeText(input: string) {
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return new TextEncoder().encode(input)
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}
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2022-03-30 20:24:25 +02:00
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export function decodeText(input?: Uint8Array, textDecoder?: TextDecoder) {
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return textDecoder
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? textDecoder.decode(input, { stream: true })
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: new TextDecoder().decode(input)
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2022-03-18 00:21:16 +01:00
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}
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export function createBufferedTransformStream(): TransformStream<
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Uint8Array,
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Uint8Array
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> {
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let bufferedString = ''
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let pendingFlush: Promise<void> | null = null
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const flushBuffer = (controller: TransformStreamDefaultController) => {
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if (!pendingFlush) {
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pendingFlush = new Promise((resolve) => {
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setTimeout(() => {
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controller.enqueue(encodeText(bufferedString))
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bufferedString = ''
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pendingFlush = null
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resolve()
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}, 0)
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})
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}
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return pendingFlush
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}
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2022-03-30 20:24:25 +02:00
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const textDecoder = new TextDecoder()
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2022-04-07 16:26:30 +02:00
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return new TransformStream({
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2022-03-18 00:21:16 +01:00
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transform(chunk, controller) {
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bufferedString += decodeText(chunk, textDecoder)
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2022-03-18 00:21:16 +01:00
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flushBuffer(controller)
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},
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flush() {
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if (pendingFlush) {
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return pendingFlush
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}
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},
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})
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}
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export function createFlushEffectStream(
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2022-04-08 16:22:25 +02:00
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handleFlushEffect: () => string
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2022-03-18 00:21:16 +01:00
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): TransformStream<Uint8Array, Uint8Array> {
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2022-04-07 16:26:30 +02:00
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return new TransformStream({
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2022-04-08 16:22:25 +02:00
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transform(chunk, controller) {
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const flushedChunk = encodeText(handleFlushEffect())
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2022-04-06 15:34:24 +02:00
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controller.enqueue(flushedChunk)
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controller.enqueue(chunk)
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2022-03-18 00:21:16 +01:00
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},
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})
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}
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2022-03-30 15:15:13 +02:00
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export async function renderToInitialStream({
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ReactDOMServer,
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element,
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}: {
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ReactDOMServer: typeof import('react-dom/server')
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element: React.ReactElement
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}): Promise<
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ReadableStream<Uint8Array> & {
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allReady?: Promise<void>
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}
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> {
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return await (ReactDOMServer as any).renderToReadableStream(element)
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}
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export async function continueFromInitialStream({
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suffix,
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dataStream,
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generateStaticHTML,
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flushEffectHandler,
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renderStream,
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}: {
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suffix?: string
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dataStream?: ReadableStream<Uint8Array>
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generateStaticHTML: boolean
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2022-04-08 16:22:25 +02:00
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flushEffectHandler?: () => string
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2022-03-30 15:15:13 +02:00
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renderStream: ReadableStream<Uint8Array> & {
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allReady?: Promise<void>
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}
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}): Promise<ReadableStream<Uint8Array>> {
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const closeTag = '</body></html>'
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const suffixUnclosed = suffix ? suffix.split(closeTag)[0] : null
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if (generateStaticHTML) {
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await renderStream.allReady
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}
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const transforms: Array<TransformStream<Uint8Array, Uint8Array>> = [
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createBufferedTransformStream(),
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flushEffectHandler ? createFlushEffectStream(flushEffectHandler) : null,
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suffixUnclosed != null ? createPrefixStream(suffixUnclosed) : null,
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dataStream ? createInlineDataStream(dataStream) : null,
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suffixUnclosed != null ? createSuffixStream(closeTag) : null,
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].filter(Boolean) as any
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return transforms.reduce(
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2022-04-07 16:26:30 +02:00
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(readable, transform) => readable.pipeThrough(transform),
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2022-03-30 15:15:13 +02:00
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renderStream
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)
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}
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2022-03-18 00:21:16 +01:00
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export async function renderToStream({
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ReactDOMServer,
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element,
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suffix,
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dataStream,
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generateStaticHTML,
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flushEffectHandler,
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}: {
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ReactDOMServer: typeof import('react-dom/server')
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element: React.ReactElement
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suffix?: string
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dataStream?: ReadableStream<Uint8Array>
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generateStaticHTML: boolean
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2022-04-08 16:22:25 +02:00
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flushEffectHandler?: () => string
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2022-03-18 00:21:16 +01:00
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}): Promise<ReadableStream<Uint8Array>> {
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2022-04-06 17:45:06 +02:00
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const renderStream = await renderToInitialStream({ ReactDOMServer, element })
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return continueFromInitialStream({
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suffix,
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dataStream,
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generateStaticHTML,
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flushEffectHandler,
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renderStream,
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})
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2022-03-18 00:21:16 +01:00
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}
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export function createSuffixStream(
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suffix: string
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): TransformStream<Uint8Array, Uint8Array> {
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2022-04-07 16:26:30 +02:00
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return new TransformStream({
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2022-03-18 00:21:16 +01:00
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flush(controller) {
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if (suffix) {
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controller.enqueue(encodeText(suffix))
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}
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},
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})
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}
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export function createPrefixStream(
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prefix: string
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): TransformStream<Uint8Array, Uint8Array> {
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let prefixFlushed = false
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let prefixPrefixFlushFinished: Promise<void> | null = null
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return new TransformStream({
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2022-03-18 00:21:16 +01:00
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transform(chunk, controller) {
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controller.enqueue(chunk)
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if (!prefixFlushed && prefix) {
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prefixFlushed = true
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prefixPrefixFlushFinished = new Promise((res) => {
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// NOTE: streaming flush
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// Enqueue prefix part before the major chunks are enqueued so that
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// prefix won't be flushed too early to interrupt the data stream
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setTimeout(() => {
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controller.enqueue(encodeText(prefix))
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res()
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})
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})
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}
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},
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flush(controller) {
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if (prefixPrefixFlushFinished) return prefixPrefixFlushFinished
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if (!prefixFlushed && prefix) {
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prefixFlushed = true
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controller.enqueue(encodeText(prefix))
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}
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},
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})
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}
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export function createInlineDataStream(
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dataStream: ReadableStream<Uint8Array>
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): TransformStream<Uint8Array, Uint8Array> {
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let dataStreamFinished: Promise<void> | null = null
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2022-04-07 16:26:30 +02:00
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return new TransformStream({
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2022-03-18 00:21:16 +01:00
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transform(chunk, controller) {
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controller.enqueue(chunk)
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if (!dataStreamFinished) {
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const dataStreamReader = dataStream.getReader()
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// NOTE: streaming flush
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// We are buffering here for the inlined data stream because the
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// "shell" stream might be chunkenized again by the underlying stream
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// implementation, e.g. with a specific high-water mark. To ensure it's
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// the safe timing to pipe the data stream, this extra tick is
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// necessary.
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dataStreamFinished = new Promise((res) =>
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setTimeout(async () => {
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try {
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while (true) {
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const { done, value } = await dataStreamReader.read()
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if (done) {
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return res()
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}
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controller.enqueue(value)
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}
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} catch (err) {
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controller.error(err)
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}
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res()
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}, 0)
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)
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}
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},
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flush() {
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if (dataStreamFinished) {
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return dataStreamFinished
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}
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},
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})
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}
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