feat: add fft/base/fftpack/ndarray/rffti

lib/node_modules/@stdlib/fft/base/fftpack/ndarray/rffti/lib/main.js

@@ -0,0 +1,83 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 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 getStride = require( '@stdlib/ndarray/base/stride' );
+var getOffset = require( '@stdlib/ndarray/base/offset' );
+var getData = require( '@stdlib/ndarray/base/data-buffer' );
+var strided = require( '@stdlib/fft/base/fftpack/rffti' );
+var ndarraylike2scalar = require( '@stdlib/ndarray/base/ndarraylike2scalar' );
+
+
+// MAIN //
+
+/**
+* Initializes a workspace array for performing a real-valued Fourier transform on a one-dimensional ndarray.
+*
+* ## Notes
+*
+* -   The function expects the following ndarrays:
+*
+*     -   a zero-dimensional ndarray containing the length of the sequence to transform.
+*     -   a one-dimensional input ndarray.
+*
+* @param {ArrayLikeObject<Object>} arrays - array-like object containing ndarrays
+* @returns {ndarrayLike} output ndarray
+*
+* @example
+* var Float64Vector = require( '@stdlib/ndarray/vector/float64' );
+* var scalar2ndarray = require( '@stdlib/ndarray/from-scalar' );
+* var Slice = require( '@stdlib/slice/ctor' );
+* var slice = require( '@stdlib/ndarray/slice' );
+*
+* var N = 8;
+* var len = scalar2ndarray( N, {
+*     'dtype': 'int32'
+* });
+*
+* var workspace = new Float64Vector( ( 2*N ) + 34 );
+*
+* var out = rffti( [ len, workspace ] );
+* // returns <ndarray>
+*
+* var bool = ( out === workspace );
+* // returns true
+*
+* var twiddleFactors = slice( workspace, new Slice( N, 2*N ) );
+* // returns <ndarray>[ ~0.707, ~0.707, 0, 0, 0, 0, 0, 0 ]
+*
+* var factors = slice( workspace, new Slice( 2*N, ( 2*N ) + 4 ) );
+* // returns <ndarray>[ 8, 2, 2, 4 ]
+*/
+function rffti( arrays ) {
+	var workspace;
+	var N;
+
+	N = ndarraylike2scalar( arrays[ 0 ] );
+	workspace = arrays[ 1 ];
+	strided( N, getData( workspace ), getStride( workspace, 0 ), getOffset( workspace ) ); // eslint-disable-line max-len
+	return workspace;
+}
+
+
+// EXPORTS //
+
+module.exports = rffti;