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denoland-deno/io/ioutil.ts

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2019-01-06 14:26:18 -05:00
// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
import { BufReader } from "./bufio.ts";
/* 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;
}