@stdlib/ndarray-base-ctor
Version:
Base multidimensional array.
99 lines (91 loc) • 2.58 kB
JavaScript
/**
* @license Apache-2.0
*
* Copyright (c) 2018 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
'use strict';
// MAIN //
/**
* Returns an array element located a specified linear view index.
*
* ## Notes
*
* - For zero-dimensional arrays, the input argument is ignored and, for clarity, should not be provided.
*
* @private
* @param {integer} [idx] - linear view index
* @returns {*} array element
*/
function iget( idx ) {
/* eslint-disable no-invalid-this */
var strides;
var shape;
var ndims;
var ind;
var s;
var i;
ndims = this._ndims;
if ( ndims === 0 ) {
if ( this._accessors ) {
return this._buffer.get( this._offset );
}
return this._buffer[ this._offset ];
}
if ( this._flags.ROW_MAJOR_CONTIGUOUS || this._flags.COLUMN_MAJOR_CONTIGUOUS ) { // eslint-disable-line max-len
// Trivial case where we have all positive strides...
if ( this._iterationOrder === 1 ) {
if ( this._accessors ) {
return this._buffer.get( this._offset+idx );
}
return this._buffer[ this._offset+idx ];
}
// Trivial case where we have all negative strides...
if ( this._iterationOrder === -1 ) {
if ( this._accessors ) {
return this._buffer.get( this.offset-idx );
}
return this._buffer[ this._offset-idx ];
}
}
// The approach which follows is to resolve a view index to its subscripts and then plug the subscripts into the standard formula for computing the linear index in the underlying data buffer...
shape = this._shape;
strides = this._strides;
ind = this._offset;
if ( this._order === 'column-major' ) {
for ( i = 0; i < ndims; i++ ) {
s = idx % shape[ i ];
idx -= s;
idx /= shape[ i ];
ind += s * strides[ i ];
}
if ( this._accessors ) {
return this._buffer.get( ind );
}
return this._buffer[ ind ];
}
// Case: row-major
for ( i = ndims-1; i >= 0; i-- ) {
s = idx % shape[ i ];
idx -= s;
idx /= shape[ i ];
ind += s * strides[ i ];
}
if ( this._accessors ) {
return this._buffer.get( ind );
}
return this._buffer[ ind ];
}
// EXPORTS //
module.exports = iget;