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limited_transform_stream.ts
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limited_transform_stream.ts
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// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
// This module is browser compatible.
/** A TransformStream that will only read & enqueue `size` amount of chunks.
*
* if options.error is set, then instead of terminating the stream,
* an error will be thrown.
*
* ```ts
* import { LimitedTransformStream } from "https://deno.land/std@$STD_VERSION/streams/limited_transform_stream.ts";
* const res = await fetch("https://example.com");
* const parts = res.body!.pipeThrough(new LimitedTransformStream(50));
* ```
*/
export class LimitedTransformStream<T> extends TransformStream<T, T> {
#read = 0;
constructor(size: number, options: { error?: boolean } = {}) {
super({
transform: (chunk, controller) => {
if ((this.#read + 1) > size) {
if (options.error) {
throw new RangeError(`Exceeded chunk limit of '${size}'`);
} else {
controller.terminate();
}
} else {
this.#read++;
controller.enqueue(chunk);
}
},
});
}
}