✨ feat(mul64): Add multiplication function.

src/index.js

@@ -4,6 +4,7 @@ export * from './big64' ;
 export * from './compare' ;
 export * from './get64' ;
 export * from './limits' ;
+export * from './mul64' ;
 export * from './not64' ;
 export * from './rotl64' ;
 export * from './rotr64' ;

src/mul64.js

@@ -0,0 +1,27 @@
+import {add64} from './add64';
+
+// TODO finish need function that multiplies two 32 bit values to 64 bit
+const mul3264 = (a, b) => {
+	const a0 = (a >>> 16) & 0xFFFF;
+	const a1 = a & 0xFFFF;
+	const b0 = (b >>> 16) & 0xFFFF;
+	const b1 = b & 0xFFFF;
+
+	const x = [Math.imul(a0,b0), Math.imul(a1, b1)];
+	const t = Math.imul(a0,b1);
+	const u = Math.imul(a1,b0);
+	const y = [(t >>> 16) | 0, (t << 16) | 0];
+	const z = [(u >>> 16) | 0, (u << 16) | 0];
+	return add64(x,add64(y,z));
+};
+
+export function mul64 (a, b) {
+
+	const [a0, a1] = a;
+	const [b0, b1] = b;
+
+	const x = [(Math.imul(a1, b0) + Math.imul(a0, b1)) | 0, 0];
+	const y = mul3264(a1, b1);
+	return add64(x, y);
+
+}

test/src/mul64.js

@@ -0,0 +1,22 @@
+import test from 'ava';
+
+import { mul64 , get64 } from '../../src' ;
+
+function macro (t, A, B, EXPECTED) {
+	const a = get64(...A);
+	const b = get64(...B);
+	const expected = get64(...EXPECTED);
+	t.deepEqual(mul64(a, b), expected, 'a * b');
+	t.deepEqual(mul64(b, a), expected, 'b * a');
+}
+
+macro.title = (providedTitle, a, b, expected) => `${providedTitle || ''} ${a} * ${b} === ${expected}`.trim();
+
+test(macro, [0x00000000, 0x00000000], [0x00000000, 0x00000000], [0x00000000, 0x00000000]);
+test(macro, [0x00000000, 0x00000001], [0x00000000, 0x00000000], [0x00000000, 0x00000000]);
+test(macro, [0x00000000, 0x00000001], [0xFFFFFFFF, 0xFFFFFFFF], [0xFFFFFFFF, 0xFFFFFFFF]);
+test(macro, [0x00000000, 0x00000002], [0xFFFFFFFF, 0xFFFFFFFF], [0xFFFFFFFF, 0xFFFFFFFE]);
+test(macro, [0xFFFFFFFF, 0xFFFFFFFF], [0xFFFFFFFF, 0xFFFFFFFF], [0x00000000, 0x00000001]);
+test(macro, [0x80000000, 0x00000000], [0x80000000, 0x00000000], [0x00000000, 0x00000000]);
+test(macro, [0x00000000, 0x80000000], [0x00000000, 0x80000000], [0x40000000, 0x00000000]);
+test(macro, [0x80000000, 0x80000000], [0x80000000, 0x80000000], [0x40000000, 0x00000000]);