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// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
function n16(n: number): number {
return n & 0xffff;
}
function n32(n: number): number {
return n >>> 0;
}
function add32WithCarry(a: number, b: number): [number, number] {
const added = n32(a) + n32(b);
return [n32(added), added > 0xffffffff ? 1 : 0];
}
function mul32WithCarry(a: number, b: number): [number, number] {
const al = n16(a);
const ah = n16(a >>> 16);
const bl = n16(b);
const bh = n16(b >>> 16);
const [t, tc] = add32WithCarry(al * bh, ah * bl);
const [n, nc] = add32WithCarry(al * bl, n32(t << 16));
const carry = nc + (tc << 16) + n16(t >>> 16) + ah * bh;
return [n, carry];
}
/**
* mul32 performs 32-bit multiplication, a * b
* @param a
* @param b
*/
export function mul32(a: number, b: number): number {
// https://stackoverflow.com/a/28151933
const al = n16(a);
const ah = a - al;
return n32(n32(ah * b) + al * b);
}
/**
* mul64 performs 64-bit multiplication with two 32-bit words
* @param [ah, al]
* @param [bh, bl]
*/
export function mul64(
[ah, al]: [number, number],
[bh, bl]: [number, number],
): [number, number] {
const [n, c] = mul32WithCarry(al, bl);
return [n32(mul32(al, bh) + mul32(ah, bl) + c), n];
}
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