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// Copyright 2018-2021 the oak authors. All rights reserved. MIT license.
import { copyBytes } from "./deps.ts";
export class AsyncIterableReader<T> implements Deno.Reader {  #asyncIterator: AsyncIterator<T>;  #closed = false;  #current: Uint8Array | undefined;  #processValue: (value: T) => Uint8Array;
  constructor(    asyncIterable: AsyncIterable<T>,    processValue: (value: T) => Uint8Array,  ) {    this.#asyncIterator = asyncIterable[Symbol.asyncIterator]();    this.#processValue = processValue;  }
  #close() {    if (this.#asyncIterator.return) {      this.#asyncIterator.return();    }    // deno-lint-ignore no-explicit-any    (this as any).#asyncIterator = undefined;    this.#closed = true;  }
  async read(p: Uint8Array): Promise<number | null> {    if (this.#closed) {      return null;    }    if (p.byteLength === 0) {      this.#close();      return 0;    }    if (!this.#current) {      const { value, done } = await this.#asyncIterator.next();      if (done) {        this.#close();      }      if (value !== undefined) {        this.#current = this.#processValue(value);      }    }    if (!this.#current) {      if (!this.#closed) {        this.#close();      }      return null;    }    const len = copyBytes(this.#current, p);    if (len >= this.#current.byteLength) {      this.#current = undefined;    } else {      this.#current = this.#current.slice(len);    }    return len;  }}