mirror of
https://github.com/denoland/deno.git
synced 2024-11-14 16:33:45 -05:00
117 lines
3.4 KiB
TypeScript
117 lines
3.4 KiB
TypeScript
// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
|
|
|
|
// TODO(ry) It'd be better to make Deferred a class that inherits from
|
|
// Promise, rather than an interface. This is possible in ES2016, however
|
|
// typescript produces broken code when targeting ES5 code.
|
|
// See https://github.com/Microsoft/TypeScript/issues/15202
|
|
// At the time of writing, the github issue is closed but the problem remains.
|
|
export interface Deferred<T> extends Promise<T> {
|
|
resolve: (value?: T | PromiseLike<T>) => void;
|
|
// eslint-disable-next-line @typescript-eslint/no-explicit-any
|
|
reject: (reason?: any) => void;
|
|
}
|
|
|
|
/** Creates a Promise with the `reject` and `resolve` functions
|
|
* placed as methods on the promise object itself. It allows you to do:
|
|
*
|
|
* const p = deferred<number>();
|
|
* // ...
|
|
* p.resolve(42);
|
|
*/
|
|
export function deferred<T>(): Deferred<T> {
|
|
let methods;
|
|
const promise = new Promise<T>((resolve, reject): void => {
|
|
methods = { resolve, reject };
|
|
});
|
|
return Object.assign(promise, methods) as Deferred<T>;
|
|
}
|
|
|
|
interface TaggedYieldedValue<T> {
|
|
iterator: AsyncIterableIterator<T>;
|
|
value: T;
|
|
}
|
|
|
|
/** The MuxAsyncIterator class multiplexes multiple async iterators into a
|
|
* single stream. It currently makes a few assumptions:
|
|
* - The iterators do not throw.
|
|
* - The final result (the value returned and not yielded from the iterator)
|
|
* does not matter; if there is any, it is discarded.
|
|
*/
|
|
export class MuxAsyncIterator<T> implements AsyncIterable<T> {
|
|
private iteratorCount = 0;
|
|
private yields: Array<TaggedYieldedValue<T>> = [];
|
|
private signal: Deferred<void> = deferred();
|
|
|
|
add(iterator: AsyncIterableIterator<T>): void {
|
|
++this.iteratorCount;
|
|
this.callIteratorNext(iterator);
|
|
}
|
|
|
|
private async callIteratorNext(
|
|
iterator: AsyncIterableIterator<T>
|
|
): Promise<void> {
|
|
const { value, done } = await iterator.next();
|
|
if (done) {
|
|
--this.iteratorCount;
|
|
} else {
|
|
this.yields.push({ iterator, value });
|
|
}
|
|
this.signal.resolve();
|
|
}
|
|
|
|
async *iterate(): AsyncIterableIterator<T> {
|
|
while (this.iteratorCount > 0) {
|
|
// Sleep until any of the wrapped iterators yields.
|
|
await this.signal;
|
|
|
|
// Note that while we're looping over `yields`, new items may be added.
|
|
for (let i = 0; i < this.yields.length; i++) {
|
|
const { iterator, value } = this.yields[i];
|
|
yield value;
|
|
this.callIteratorNext(iterator);
|
|
}
|
|
|
|
// Clear the `yields` list and reset the `signal` promise.
|
|
this.yields.length = 0;
|
|
this.signal = deferred();
|
|
}
|
|
}
|
|
|
|
[Symbol.asyncIterator](): AsyncIterableIterator<T> {
|
|
return this.iterate();
|
|
}
|
|
}
|
|
|
|
/** Collects all Uint8Arrays from an AsyncIterable and retuns a single
|
|
* Uint8Array with the concatenated contents of all the collected arrays.
|
|
*/
|
|
export async function collectUint8Arrays(
|
|
it: AsyncIterable<Uint8Array>
|
|
): Promise<Uint8Array> {
|
|
const chunks = [];
|
|
let length = 0;
|
|
for await (const chunk of it) {
|
|
chunks.push(chunk);
|
|
length += chunk.length;
|
|
}
|
|
if (chunks.length === 1) {
|
|
// No need to copy.
|
|
return chunks[0];
|
|
}
|
|
const collected = new Uint8Array(length);
|
|
let offset = 0;
|
|
for (const chunk of chunks) {
|
|
collected.set(chunk, offset);
|
|
offset += chunk.length;
|
|
}
|
|
return collected;
|
|
}
|
|
|
|
// Delays the given milliseconds and resolves.
|
|
export function delay(ms: number): Promise<void> {
|
|
return new Promise((res): number =>
|
|
setTimeout((): void => {
|
|
res();
|
|
}, ms)
|
|
);
|
|
}
|