@oazmi/build-tools/esm/deps/jsr.io/@std/io/0.223.0/copy_n.js

general deno build tool scripts which I practically use in all of my typescript repos

// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
// This module is browser compatible.
import { assert } from "../../assert/0.223.0/assert.js";
const DEFAULT_BUFFER_SIZE = 32 * 1024;
/**
 * Copy N size at the most. If read size is lesser than N, then returns nread
 * @param r Reader
 * @param dest Writer
 * @param size Read size
 *
 * @deprecated (will be removed after 1.0.0) Use the {@link https://developer.mozilla.org/en-US/docs/Web/API/Streams_API | Web Streams API} instead.
 */
export async function copyN(r, dest, size) {
    let bytesRead = 0;
    let buf = new Uint8Array(DEFAULT_BUFFER_SIZE);
    while (bytesRead < size) {
        if (size - bytesRead < DEFAULT_BUFFER_SIZE) {
            buf = new Uint8Array(size - bytesRead);
        }
        const result = await r.read(buf);
        const nread = result ?? 0;
        bytesRead += nread;
        if (nread > 0) {
            let n = 0;
            while (n < nread) {
                n += await dest.write(buf.slice(n, nread));
            }
            assert(n === nread, "could not write");
        }
        if (result === null) {
            break;
        }
    }
    return bytesRead;
}