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* @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';
// MODULES //
var isColumnMajor = require( '@stdlib/ndarray/base/assert/is-column-major-string' );
var trunc = require( '@stdlib/math/base/special/trunc' );
var format = require( '@stdlib/string/format' );
// MAIN //
/**
* Converts a linear index to an array of subscripts.
*
* @param {NonNegativeIntegerArray} shape - array shape
* @param {IntegerArray} strides - stride array
* @param {NonNegativeInteger} offset - location of the first indexed value **based** on the stride array
* @param {string} order - specifies whether an array is row-major (C-style) or column-major (Fortran-style)
* @param {integer} idx - linear index
* @param {string} mode - specifies how to handle a linear index which exceeds array dimensions
* @param {(Array|TypedArray|Object)} out - destination object
* @throws {RangeError} linear index must not exceed array dimensions
* @returns {(Array|TypedArray|Object)} subscripts
*
* @example
* var shape = [ 3, 3, 3 ];
* var strides = [ 9, 6, 1 ];
* var offset = 0;
* var order = 'row-major';
*
* var s = [ 0, 0, 0 ];
* var out = ind2sub( shape, strides, offset, order, 17, 'throw', s );
* // returns [ 1, 2, 2 ]
*
* var bool = ( out === s );
* // returns true
*/
function ind2sub( shape, strides, offset, order, idx, mode, out ) {
var ndims;
var len;
var k;
var s;
var i;
ndims = shape.length;
len = 1;
for ( i = 0; i < ndims; i++ ) {
len *= shape[ i ];
}
if ( mode === 'clamp' ) {
if ( idx < 0 ) {
idx = 0;
} else if ( idx >= len ) {
idx = len - 1;
}
} else if ( mode === 'wrap' ) {
if ( idx < 0 ) {
idx += len; // slight optimization to avoid modulo arithmetic when |idx| <= len
if ( idx < 0 ) {
idx %= len;
if ( idx !== 0 ) {
idx += len;
}
}
} else if ( idx >= len ) {
idx -= len; // slight optimization to avoid modulo arithmetic when len < idx <= 2*len
if ( idx >= len ) {
idx %= len;
}
}
} else {
if ( mode === 'normalize' && idx < 0 ) {
idx += len;
}
if ( idx < 0 || idx >= len ) {
throw new RangeError( format( 'invalid argument. Linear index must not exceed array dimensions. Number of array elements: `%u`. Value: `%d`.', len, idx ) );
}
}
if ( offset === 0 ) {
if ( isColumnMajor( order ) ) {
for ( i = 0; i < ndims; i++ ) {
s = idx % shape[ i ];
idx -= s;
idx /= shape[ i ];
out[ i ] = s;
}
return out;
}
// Case: row-major
for ( i = ndims-1; i >= 0; i-- ) {
s = idx % shape[ i ];
idx -= s;
idx /= shape[ i ];
out[ i ] = s;
}
return out;
}
if ( isColumnMajor( order ) ) {
for ( i = ndims-1; i >= 0; i-- ) {
s = strides[ i ];
if ( s < 0 ) {
k = trunc( idx/s );
idx -= k * s;
out[ i ] = shape[ i ] - 1 + k;
} else {
k = trunc( idx/s );
idx -= k * s;
out[ i ] = k;
}
}
return out;
}
// Case: row-major
for ( i = 0; i < ndims; i++ ) {
s = strides[ i ];
if ( s < 0 ) {
k = trunc( idx/s );
idx -= k * s;
out[ i ] = shape[ i ] - 1 + k;
} else {
k = trunc( idx/s );
idx -= k * s;
out[ i ] = k;
}
}
return out;
}
// EXPORTS //
module.exports = ind2sub;
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