57 lines
1.4 KiB
JavaScript
57 lines
1.4 KiB
JavaScript
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/**
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* @license Apache-2.0
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*
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* Copyright (c) 2018 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict';
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// MAIN //
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/**
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* Returns the index offset which specifies the location of the first indexed value in a multidimensional array based on a stride array.
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*
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* @param {NonNegativeIntegerArray} shape - array shape
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* @param {IntegerArray} strides - stride array
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* @returns {NonNegativeInteger} offset - offset
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*
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* @example
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* var shape = [ 2, 3, 10 ];
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* var strides = [ 30, -10, 1 ];
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*
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* var offset = strides2offset( shape, strides );
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* // returns 20
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*/
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function strides2offset( shape, strides ) {
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var offset;
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var ndims;
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var i;
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ndims = shape.length;
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offset = 0;
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for ( i = 0; i < ndims; i++ ) {
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if ( strides[ i ] < 0 ) {
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// Note that, since the stride is negative, this operation increments, not decrements, the offset...
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offset -= strides[ i ] * ( shape[ i ]-1 );
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}
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}
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return offset;
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}
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// EXPORTS //
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module.exports = strides2offset;
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