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std/hash/_fnv/util.ts

Deno standard library
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// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
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];}