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* @license Apache-2.0
*
* Copyright (c) 2018 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
'use strict';
// MODULES //
var imul = require( '@stdlib/number/int32/base/mul' );
// VARIABLES //
// Define a mask for the least significant 16 bits (low word): 65535 => 0x0000ffff => 00000000000000001111111111111111
var LOW_WORD_MASK = 0x0000ffff>>>0; // asm type annotation
// MAIN //
/**
* Performs multiplication of two signed 32-bit integers and returns an array of two signed 32-bit integers which represents the signed 64-bit integer product.
*
* @param {uinteger32} a - integer
* @param {uinteger32} b - integer
* @param {Collection} out - output array
* @param {integer} stride - output array stride
* @param {NonNegativeInteger} offset - output array index offset
* @returns {Collection} output array
*
* @example
* var v = imuldw( 0xAAAAAAAA, 0x55555555, [ 0, 0 ], 1, 0 );
* // returns [ -477218589, 1908874354 ]
*/
function imuldw( a, b, out, stride, offset ) {
var w1;
var w2;
var ha;
var hb;
var la;
var lb;
var t;
var k;
a |= 0; // asm type annotation
b |= 0; // asm type annotation
ha = ( a >> 16 ) | 0;
la = ( a & LOW_WORD_MASK ) >>> 0;
hb = ( b >> 16 ) | 0;
lb = ( b & LOW_WORD_MASK ) >>> 0;
t = ( la*lb ) >>> 0;
k = ( t >>> 16 ) >>> 0;
t = ( ( ha*lb ) + k ) >>> 0;
w2 = ( t & LOW_WORD_MASK ) >>> 0;
w1 = ( t >> 16 ) >>> 0;
t = ( ( la*hb ) + w2 ) >>> 0;
k = ( t >> 16 ) >>> 0;
out[ offset ] = ( ( ha*hb ) + w1 + k ) | 0; // compute the higher 32 bits and cast to a signed 32-bit integer
out[ offset + stride ] = imul( a, b ) | 0; // compute the lower 32 bits and cast to a signed 32-bit integer
return out;
}
// EXPORTS //
module.exports = imuldw;
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