main.js (2174B)
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 38 // MAIN // 39 40 /** 41 * Converts an integer-valued double-precision floating-point number to a signed 64-bit integer byte array according to host byte order (endianness). 42 * 43 * ## Notes 44 * 45 * - This function assumes that the input value is less than the maximum safe double-precision floating-point integer plus one (i.e., `2**53`). 46 * 47 * @param {number} x - input value 48 * @returns {Uint8Array} byte array 49 * 50 * @example 51 * var bytes = float64ToInt64Bytes( 1.0 ); 52 * // returns <Uint8Array> 53 */ 54 function float64ToInt64Bytes( x ) { 55 var bytes; 56 var view; 57 var hi; 58 var lo; 59 60 bytes = new Uint8Array( 8 ); 61 if ( x === 0 ) { 62 return bytes; 63 } 64 // Get the low 32-bit word: 65 lo = (x&LOW_MASK)>>>0; 66 67 // Get the high 32-bit word: 68 hi = floor( x/TWO_32 ); 69 70 // Insert the high and low words according to host byte order (endianness): 71 view = new DataView( bytes.buffer ); 72 if ( IS_LITTLE_ENDIAN ) { 73 view.setUint32( 0, lo, IS_LITTLE_ENDIAN ); 74 view.setUint32( 4, hi, IS_LITTLE_ENDIAN ); 75 } else { 76 view.setUint32( 0, hi, IS_LITTLE_ENDIAN ); 77 view.setUint32( 4, lo, IS_LITTLE_ENDIAN ); 78 } 79 return bytes; 80 } 81 82 83 // EXPORTS // 84 85 module.exports = float64ToInt64Bytes;