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