vscode/src/vs/base/common/bits/bits.ts

/*---------------------------------------------------------------------------------------------
 *  Copyright (c) Microsoft Corporation. All rights reserved.
 *  Licensed under the MIT License. See License.txt in the project root for license information.
 *--------------------------------------------------------------------------------------------*/
'use strict';

export function leftPad(value: string, length: number, char: string = '0'): string {
	return new Array(length - value.length + 1).join(char) + value;
}

export function toHexString(value: number, bitsize: number = 32): string {
	return leftPad((value >>> 0).toString(16), bitsize / 4);
}

export function leftRotate(value: number, bits: number, totalBits: number = 32): number {
	// delta + bits = totalBits
	var delta = totalBits - bits;

	// All ones, expect `delta` zeros aligned to the right
	var mask = ~((1 << delta) - 1);

	// Join (value left-shifted `bits` bits) with (masked value right-shifted `delta` bits)
	return ((value << bits) | ((mask & value) >>> delta)) >>> 0;
}

export function multiply64(a: number, b: number): number[] {
	/*                      A1        A0   => A
	 *                      B1        B0   => B
	 *	               B0 * A1   B0 * A0
	 *         B1 * A1   B1 * A0
	 *	C3        C2        C1        C0   => C
	*/

	var a0 = a & 0xffff, a1 = a >>> 16;
	var b0 = b & 0xffff, b1 = b >>> 16;
	var c0 = 0, c1 = 0, c2 = 0, c3 = 0;

	var x = b0 * a0;
	c0 += x & 0xffff;
	c1 += x >>> 16;

	x = b0 * a1;
	c1 += x & 0xffff;
	c2 += x >>> 16;

	x = b1 * a0;
	c1 += x & 0xffff;
	c2 += x >>> 16;

	c2 += c1 >>> 16;
	c1 = c1 & 0xffff;

	x = b1 * a1;
	c2 += x & 0xffff;
	c3 += x >>> 16;

	c3 += c2 >>> 16;
	c2 = c2 & 0xffff;

	return [(c3 << 16 | c2) >>> 0, (c1 << 16 | c0) >>> 0];
}