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// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
import { BufReader } from "./bufio.ts";
import { Reader, Writer } from "deno";
import { assert } from "../testing/asserts.ts";
/** copy N size at the most. If read size is lesser than N, then returns nread */
export async function copyN(
dest: Writer,
r: Reader,
size: number
): Promise<number> {
let bytesRead = 0;
let buf = new Uint8Array(1024);
while (bytesRead < size) {
if (size - bytesRead < 1024) {
buf = new Uint8Array(size - bytesRead);
}
const { nread, eof } = await r.read(buf);
bytesRead += nread;
if (nread > 0) {
const n = await dest.write(buf.slice(0, nread));
assert(n === nread, "could not write");
}
if (eof) {
break;
}
}
return bytesRead;
}
/** Read big endian 16bit short from BufReader */
export async function readShort(buf: BufReader): Promise<number> {
const [high, low] = [await buf.readByte(), await buf.readByte()];
return (high << 8) | low;
}
/** Read big endian 32bit integer from BufReader */
export async function readInt(buf: BufReader): Promise<number> {
const [high, low] = [await readShort(buf), await readShort(buf)];
return (high << 16) | low;
}
const BIT32 = 0xffffffff;
/** Read big endian 64bit long from BufReader */
export async function readLong(buf: BufReader): Promise<number> {
const [high, low] = [await readInt(buf), await readInt(buf)];
// ECMAScript doesn't support 64bit bit ops.
return high ? high * (BIT32 + 1) + low : low;
}
/** Slice number into 64bit big endian byte array */
export function sliceLongToBytes(d: number, dest = new Array(8)): number[] {
let mask = 0xff;
let low = (d << 32) >>> 32;
let high = (d - low) / (BIT32 + 1);
let shift = 24;
for (let i = 0; i < 4; i++) {
dest[i] = (high >>> shift) & mask;
dest[i + 4] = (low >>> shift) & mask;
shift -= 8;
}
return dest;
}
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