assign.js (2644B)
1 /** 2 * @license Apache-2.0 3 * 4 * Copyright (c) 2021 The Stdlib Authors. 5 * 6 * Licensed under the Apache License, Version 2.0 (the "License"); 7 * you may not use this file except in compliance with the License. 8 * You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 */ 18 19 'use strict'; 20 21 // MODULES // 22 23 var IS_LITTLE_ENDIAN = require( '@stdlib/assert/is-little-endian' ); 24 var Uint8Array = require( '@stdlib/array/uint8' ); 25 var DataView = require( '@stdlib/array/dataview' ); 26 var floor = require( '@stdlib/math/base/special/floor' ); 27 28 29 // VARIABLES // 30 31 // 0xFFFFFFFF = 2**32 - 1 => 11111111 11111111 11111111 11111111 32 var LOW_MASK = 0xFFFFFFFF >>> 0; 33 34 // 2**32 35 var TWO_32 = 4294967296; 36 37 // Byte array workspace: 38 var BYTES = new Uint8Array( 8 ); 39 var VIEW = new DataView( BYTES.buffer ); 40 41 42 // MAIN // 43 44 /** 45 * Converts an integer-valued double-precision floating-point number to a signed 64-bit integer byte array according to host byte order (endianness). 46 * 47 * ## Notes 48 * 49 * - This function assumes that the input value is less than the maximum safe double-precision floating-point integer plus one (i.e., `2**53`). 50 * 51 * @param {number} x - input value 52 * @param {Collection} out - output array 53 * @param {integer} stride - output array stride 54 * @param {NonNegativeInteger} offset - output array index offset 55 * @returns {Collection} output array 56 * 57 * @example 58 * var Uint8Array = require( '@stdlib/array/uint8' ); 59 * 60 * var out = new Uint8Array( 8 ); 61 * var bytes = float64ToInt64Bytes( 1.0, out, 1, 0 ); 62 * // returns <Uint8Array> 63 */ 64 function float64ToInt64Bytes( x, out, stride, offset ) { 65 var hi; 66 var lo; 67 var i; 68 69 if ( x === 0 ) { 70 for ( i = 0; i < BYTES.length; i++ ) { 71 out[ offset ] = 0; 72 offset += stride; 73 } 74 return out; 75 } 76 // Get the low 32-bit word: 77 lo = (x&LOW_MASK)>>>0; 78 79 // Get the high 32-bit word: 80 hi = floor( x/TWO_32 ); 81 82 // Insert the high and low words according to host byte order (endianness): 83 if ( IS_LITTLE_ENDIAN ) { 84 VIEW.setUint32( 0, lo, IS_LITTLE_ENDIAN ); 85 VIEW.setUint32( 4, hi, IS_LITTLE_ENDIAN ); 86 } else { 87 VIEW.setUint32( 0, hi, IS_LITTLE_ENDIAN ); 88 VIEW.setUint32( 4, lo, IS_LITTLE_ENDIAN ); 89 } 90 for ( i = 0; i < BYTES.length; i++ ) { 91 out[ offset ] = BYTES[ i ]; 92 offset += stride; 93 } 94 return out; 95 } 96 97 98 // EXPORTS // 99 100 module.exports = float64ToInt64Bytes;