107 lines
2.5 KiB
JavaScript
107 lines
2.5 KiB
JavaScript
/**
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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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* Computes the minimum and maximum linear indices in an underlying data buffer which are accessible to an array view and assigns results to a provided output 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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* @param {NonNegativeInteger} offset - index offset
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* @param {(Array|TypedArray|Object)} out - output object
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* @returns {(Array|TypedArray|Object)} linear indices
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*
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* @example
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* var shape = [ 10, 10 ];
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* var strides = [ 10, 1 ];
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* var offset = 10;
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*
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* var out = [ 0, 0 ];
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* var idx = minmaxViewBufferIndex( shape, strides, offset, out );
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* // returns [ 10, 109 ]
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*
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* var bool = ( idx === out );
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* // returns true
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*
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* @example
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* var shape = [ 10, 10 ];
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* var strides = [ -10, -1 ];
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* var offset = 99;
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*
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* var out = [ 0, 0 ];
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* var idx = minmaxViewBufferIndex( shape, strides, offset, out );
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* // returns [ 0, 99 ]
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*
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* var bool = ( idx === out );
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* // returns true
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*
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* @example
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* var shape = [ 10, 10 ];
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* var strides = [ 1, 10 ];
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* var offset = 10;
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*
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* var out = [ 0, 0 ];
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* var idx = minmaxViewBufferIndex( shape, strides, offset, out );
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* // returns [ 10, 109 ]
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*
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* var bool = ( idx === out );
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* // returns true
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*
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* @example
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* var shape = [ 10, 10 ];
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* var strides = [ -1, -10 ];
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* var offset = 99;
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*
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* var out = [ 0, 0 ];
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* var idx = minmaxViewBufferIndex( shape, strides, offset, out );
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* // returns [ 0, 99 ]
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*
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* var bool = ( idx === out );
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* // returns true
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*/
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function minmaxViewBufferIndex( shape, strides, offset, out ) {
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var ndims;
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var min;
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var max;
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var s;
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var i;
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ndims = shape.length;
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min = offset;
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max = offset;
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for ( i = 0; i < ndims; i++ ) {
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s = strides[ i ];
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if ( s > 0 ) {
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max += s * ( shape[i]-1 );
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} else if ( s < 0 ) {
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min += s * ( shape[i]-1 ); // decrements min
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}
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}
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out[ 0 ] = min;
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out[ 1 ] = max;
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return out;
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}
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// EXPORTS //
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module.exports = minmaxViewBufferIndex;
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