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zip_readable_streams.ts
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zip_readable_streams.ts
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// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
// This module is browser compatible.
/**
* Merge multiple streams into a single one, taking order into account, and each stream
* will wait for a chunk to enqueue before the next stream can append another chunk.
* If a stream ends before other ones, the others will continue adding data in order,
* and the finished one will not add any more data.
*/
export function zipReadableStreams<T>(
...streams: ReadableStream<T>[]
): ReadableStream<T> {
const readers = streams.map((s) => s.getReader());
return new ReadableStream<T>({
async start(controller) {
try {
let resolved = 0;
while (resolved != streams.length) {
for (const [key, reader] of Object.entries(readers)) {
const { value, done } = await reader.read();
if (!done) {
controller.enqueue(value!);
} else {
resolved++;
readers.splice(+key, 1);
}
}
}
controller.close();
} catch (e) {
controller.error(e);
}
},
});
}