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* @license Apache-2.0
*
* Copyright (c) 2023 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 isNonNegativeInteger = require( '@stdlib/assert/is-nonnegative-integer' ).isPrimitive;
var allocUnsafe = require( '@stdlib/buffer/alloc-unsafe' );
var ctors = require( '@stdlib/array/typed-ctors' );
var zeros = require( '@stdlib/array/base/zeros' );
var bytesPerElement = require( '@stdlib/ndarray/base/bytes-per-element' );
var defaults = require( '@stdlib/array/defaults' );
var format = require( '@stdlib/string/format' );
// VARIABLES //
var DEFAULT_DTYPE = defaults.get( 'dtypes.default' );
// MAIN //
/**
* Creates an uninitialized array having a specified length.
*
* @param {NonNegativeInteger} length - array length
* @param {string} [dtype="float64"] - data type
* @throws {TypeError} first argument must be a nonnegative integer
* @throws {TypeError} second argument must be a recognized data type
* @returns {(TypedArray|Array|ComplexArray)} array or typed array
*
* @example
* var arr = empty( 2 );
* // returns <Float64Array>
*
* @example
* var arr = empty( 2, 'float32' );
* // returns <Float32Array>
*/
function empty( length ) {
var nbytes;
var offset;
var dtype;
var ctor;
var buf;
var out;
var nb;
if ( !isNonNegativeInteger( length ) ) {
throw new TypeError( format( 'invalid argument. First argument must be a nonnegative integer. Value: `%s`.', length ) );
}
if ( arguments.length > 1 ) {
dtype = arguments[ 1 ];
} else {
dtype = DEFAULT_DTYPE;
}
if ( dtype === 'generic' ) {
return zeros( length );
}
nbytes = bytesPerElement( dtype );
if ( nbytes === null ) {
throw new TypeError( format( 'invalid argument. Second argument must be a supported data type. Value: `%s`.', dtype ) );
}
// Resolve typed array constructor:
ctor = ctors( dtype );
// Compute the number of bytes to allocate:
nb = nbytes * length;
if ( dtype === 'complex128' ) {
nb += 8; // Note: need to allocate additional bytes to ensure alignment
}
// Allocate binary buffer:
buf = allocUnsafe( nb );
// Resolve the byte offset:
offset = buf.byteOffset;
if ( dtype === 'complex128' ) {
if ( !isNonNegativeInteger( offset/nbytes ) ) {
offset += 8; // Note: ensure alignment
}
}
// Reinterpret the binary buffer:
out = new ctor( buf.buffer, offset, length );
return out;
}
// EXPORTS //
module.exports = empty;
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