main.js (2073B)
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 * Computes the minimum and maximum linear indices in an underlying data buffer which are accessible to an array view. 25 * 26 * @param {NonNegativeIntegerArray} shape - array shape 27 * @param {IntegerArray} strides - stride array 28 * @param {NonNegativeInteger} offset - index offset 29 * @returns {Array} linear indices 30 * 31 * @example 32 * var shape = [ 10, 10 ]; 33 * var strides = [ 10, 1 ]; 34 * var offset = 10; 35 * 36 * var idx = minmaxViewBufferIndex( shape, strides, offset ); 37 * // returns [ 10, 109 ] 38 * 39 * @example 40 * var shape = [ 10, 10 ]; 41 * var strides = [ -10, -1 ]; 42 * var offset = 99; 43 * 44 * var idx = minmaxViewBufferIndex( shape, strides, offset ); 45 * // returns [ 0, 99 ] 46 * 47 * @example 48 * var shape = [ 10, 10 ]; 49 * var strides = [ 1, 10 ]; 50 * var offset = 10; 51 * 52 * var idx = minmaxViewBufferIndex( shape, strides, offset ); 53 * // returns [ 10, 109 ] 54 * 55 * @example 56 * var shape = [ 10, 10 ]; 57 * var strides = [ -1, -10 ]; 58 * var offset = 99; 59 * 60 * var idx = minmaxViewBufferIndex( shape, strides, offset ); 61 * // returns [ 0, 99 ] 62 */ 63 function minmaxViewBufferIndex( shape, strides, offset ) { 64 var ndims; 65 var min; 66 var max; 67 var s; 68 var i; 69 70 ndims = shape.length; 71 min = offset; 72 max = offset; 73 for ( i = 0; i < ndims; i++ ) { 74 s = strides[ i ]; 75 if ( s > 0 ) { 76 max += s * ( shape[i]-1 ); 77 } else if ( s < 0 ) { 78 min += s * ( shape[i]-1 ); // decrements min 79 } 80 } 81 return [ min, max ]; 82 } 83 84 85 // EXPORTS // 86 87 module.exports = minmaxViewBufferIndex;