main.js (1480B)
1 /** 2 * @license Apache-2.0 3 * 4 * Copyright (c) 2018 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 // MAIN // 22 23 /** 24 * Returns the index offset which specifies the location of the first indexed value in a multidimensional array based on a stride array. 25 * 26 * @param {NonNegativeIntegerArray} shape - array shape 27 * @param {IntegerArray} strides - stride array 28 * @returns {NonNegativeInteger} offset - offset 29 * 30 * @example 31 * var shape = [ 2, 3, 10 ]; 32 * var strides = [ 30, -10, 1 ]; 33 * 34 * var offset = strides2offset( shape, strides ); 35 * // returns 20 36 */ 37 function strides2offset( shape, strides ) { 38 var offset; 39 var ndims; 40 var i; 41 42 ndims = shape.length; 43 offset = 0; 44 for ( i = 0; i < ndims; i++ ) { 45 if ( strides[ i ] < 0 ) { 46 // Note that, since the stride is negative, this operation increments, not decrements, the offset... 47 offset -= strides[ i ] * ( shape[ i ]-1 ); 48 } 49 } 50 return offset; 51 } 52 53 54 // EXPORTS // 55 56 module.exports = strides2offset;