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// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
import { DEFAULT_BUFFER_SIZE } from "./_common.ts";
/** Copies from `src` to `dst` until either EOF (`null`) is read from `src` or * an error occurs. It resolves to the number of bytes copied or rejects with * the first error encountered while copying. * * ```ts * import { copy } from "https://deno.land/std@$STD_VERSION/streams/copy.ts"; * * const source = await Deno.open("my_file.txt"); * const bytesCopied1 = await copy(source, Deno.stdout); * const destination = await Deno.create("my_file_2.txt"); * const bytesCopied2 = await copy(source, destination); * ``` * * @param src The source to copy from * @param dst The destination to copy to * @param options Can be used to tune size of the buffer. Default size is 32kB */export async function copy(  src: Deno.Reader,  dst: Deno.Writer,  options?: {    bufSize?: number;  },): Promise<number> {  let n = 0;  const bufSize = options?.bufSize ?? DEFAULT_BUFFER_SIZE;  const b = new Uint8Array(bufSize);  let gotEOF = false;  while (gotEOF === false) {    const result = await src.read(b);    if (result === null) {      gotEOF = true;    } else {      let nwritten = 0;      while (nwritten < result) {        nwritten += await dst.write(b.subarray(nwritten, result));      }      n += nwritten;    }  }  return n;}