feat: add blas/ext/base/dcircshift

lib/node_modules/@stdlib/blas/ext/base/dcircshift/README.md

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+<!--
+
+@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.
+
+-->
+
+# dcircshift
+
+> Perform a circular shift on a double-precision floating-point strided array in-place.
+
+<section class="usage">
+
+## Usage
+
+```javascript
+var dcircshift = require( '@stdlib/blas/ext/base/dcircshift' );
+```
+
+#### dcircshift( N, k, x, strideX )
+
+Performs a circular shift on a double-precision floating-point strided array in-place.
+
+```javascript
+var Float64Array = require( '@stdlib/array/float64' );
+
+var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0 ] );
+
+dcircshift( x.length, 2, x, 1 );
+// x => <Float64Array>[ 4.0, 5.0, 1.0, 2.0, 3.0 ]
+```
+
+The function has the following parameters:
+
+-   **N**: number of indexed elements.
+-   **k**: number of positions to shift.
+-   **x**: input [`Float64Array`][@stdlib/array/float64].
+-   **strideX**: stride length.
+
+The `N` and stride parameters determine which elements in the strided array are accessed at runtime. For example, to circularly shift every other element:
+
+```javascript
+var Float64Array = require( '@stdlib/array/float64' );
+
+var x = new Float64Array( [ 1.0, 0.0, 2.0, 0.0, 3.0, 0.0, 4.0, 0.0 ] );
+
+dcircshift( 4, 1, x, 2 );
+// x => <Float64Array>[ 4.0, 0.0, 1.0, 0.0, 2.0, 0.0, 3.0, 0.0 ]
+```
+
+Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.
+
+```javascript
+var Float64Array = require( '@stdlib/array/float64' );
+
+// Initial array...
+var x0 = new Float64Array( [ 0.0, 1.0, 2.0, 3.0, 4.0, 5.0 ] );
+
+// Create an offset view...
+var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
+
+// Circularly shift elements in the view:
+dcircshift( 5, 2, x1, 1 );
+// x0 => <Float64Array>[ 0.0, 4.0, 5.0, 1.0, 2.0, 3.0 ]
+```
+
+#### dcircshift.ndarray( N, k, x, strideX, offsetX )
+
+Performs a circular shift on a double-precision floating-point strided array in-place using alternative indexing semantics.
+
+```javascript
+var Float64Array = require( '@stdlib/array/float64' );
+
+var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0 ] );
+
+dcircshift.ndarray( x.length, 2, x, 1, 0 );
+// x => <Float64Array>[ 4.0, 5.0, 1.0, 2.0, 3.0 ]
+```
+
+The function has the following additional parameters:
+
+-   **offsetX**: starting index.
+
+While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying buffer, the offset parameter supports indexing semantics based on a starting index. For example, to access only the last three elements of the strided array:
+
+```javascript
+var Float64Array = require( '@stdlib/array/float64' );
+
+var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
+
+dcircshift.ndarray( 3, 1, x, 1, x.length-3 );
+// x => <Float64Array>[ 1.0, 2.0, 3.0, 6.0, 4.0, 5.0 ]
+```
+
+</section>
+
+<!-- /.usage -->
+
+<section class="notes">
+
+## Notes
+
+-   If `N <= 0`, both functions return the strided array unchanged.
+-   If `k` is a multiple of `N`, both functions return the strided array unchanged.
+-   If `k > 0` elements are shifted to the right.
+-   If `k < 0` elements are shifted to the left.
+
+</section>
+
+<!-- /.notes -->
+
+<section class="examples">
+
+## Examples
+
+<!-- eslint no-undef: "error" -->
+
+```javascript
+var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
+var dcircshift = require( '@stdlib/blas/ext/base/dcircshift' );
+
+var x = discreteUniform( 10, -100, 100, {
+    'dtype': 'float64'
+});
+console.log( x );
+
+dcircshift( x.length, 3, x, 1 );
+console.log( x );
+```
+
+</section>
+
+<!-- /.examples -->
+
+<!-- C interface documentation. -->
+
+* * *
+
+<section class="c">
+
+## C APIs
+
+<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
+
+<section class="intro">
+
+</section>
+
+<!-- /.intro -->
+
+<!-- C usage documentation. -->
+
+<section class="usage">
+
+### Usage
+
+```c
+#include "stdlib/blas/ext/base/dcircshift.h"
+```
+
+#### stdlib_strided_dcircshift( N, k, \*X, strideX )
+
+Performs a circular shift on a double-precision floating-point strided array in-place.
+
+```c
+double x[] = { 1.0, 2.0, 3.0, 4.0, 5.0 };
+
+stdlib_strided_dcircshift( 5, 2, x, 1 );
+```
+
+The function accepts the following arguments:
+
+-   **N**: `[in] CBLAS_INT` number of indexed elements.
+-   **k**: `[in] CBLAS_INT` number of positions to shift.
+-   **X**: `[inout] double*` input array.
+-   **strideX**: `[in] CBLAS_INT` stride length.
+
+```c
+void stdlib_strided_dcircshift( const CBLAS_INT N, const CBLAS_INT k, double *X, const CBLAS_INT strideX );
+```
+
+#### stdlib_strided_dcircshift_ndarray( N, k, \*X, strideX, offsetX )
+
+Performs a circular shift on a double-precision floating-point strided array in-place using alternative indexing semantics.
+
+```c
+double x[] = { 1.0, 2.0, 3.0, 4.0, 5.0 };
+
+stdlib_strided_dcircshift_ndarray( 5, 2, x, 1, 0 );
+```
+
+The function accepts the following arguments:
+
+-   **N**: `[in] CBLAS_INT` number of indexed elements.
+-   **k**: `[in] CBLAS_INT` number of positions to shift.
+-   **X**: `[inout] double*` input array.
+-   **strideX**: `[in] CBLAS_INT` stride length.
+-   **offsetX**: `[in] CBLAS_INT` starting index.
+
+```c
+void stdlib_strided_dcircshift_ndarray( const CBLAS_INT N, const CBLAS_INT k, double *X, const CBLAS_INT strideX, const CBLAS_INT offsetX );
+```
+
+</section>
+
+<!-- /.usage -->
+
+<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="notes">
+
+</section>
+
+<!-- /.notes -->
+
+<!-- C API usage examples. -->
+
+<section class="examples">
+
+### Examples
+
+```c
+#include "stdlib/blas/ext/base/dcircshift.h"
+#include <stdio.h>
+
+int main( void ) {
+    // Create a strided array:
+    double x[] = { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 };
+
+    // Specify the number of elements:
+    const int N = 8;
+
+    // Specify the shift amount:
+    const int k = 3;
+
+    // Specify a stride:
+    const int strideX = 1;
+
+    // Perform the circular shift:
+    stdlib_strided_dcircshift( N, k, x, strideX );
+
+    // Print the result:
+    for ( int i = 0; i < 8; i++ ) {
+        printf( "x[ %i ] = %lf\n", i, x[ i ] );
+    }
+}
+```
+
+</section>
+
+<!-- /.examples -->
+
+</section>
+
+<!-- /.c -->
+
+<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->
+
+<section class="related">
+
+</section>
+
+<!-- /.related -->
+
+<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="links">
+
+[@stdlib/array/float64]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/float64
+
+[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
+
+<!-- <related-links> -->
+
+<!-- </related-links> -->
+
+</section>
+
+<!-- /.links -->

lib/node_modules/@stdlib/blas/ext/base/dcircshift/benchmark/benchmark.js

@@ -0,0 +1,100 @@
+/**
+* @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 bench = require( '@stdlib/bench' );
+var uniform = require( '@stdlib/random/array/uniform' );
+var isnan = require( '@stdlib/math/base/assert/is-nan' );
+var pow = require( '@stdlib/math/base/special/pow' );
+var floor = require( '@stdlib/math/base/special/floor' );
+var format = require( '@stdlib/string/format' );
+var pkg = require( './../package.json' ).name;
+var dcircshift = require( './../lib/dcircshift.js' );
+
+
+// VARIABLES //
+
+var options = {
+	'dtype': 'float64'
+};
+
+
+// FUNCTIONS //
+
+/**
+* Create a benchmark function.
+*
+* @private
+* @param {PositiveInteger} len - array length
+* @returns {Function} benchmark function
+*/
+function createBenchmark( len ) {
+	var x = uniform( len, -10.0, 10.0, options );
+	var k = floor( len / 2 );
+	return benchmark;
+
+	/**
+	* Benchmark function.
+	*
+	* @private
+	* @param {Benchmark} b - benchmark instance
+	*/
+	function benchmark( b ) {
+		var y;
+		var i;
+
+		b.tic();
+		for ( i = 0; i < b.iterations; i++ ) {
+			y = dcircshift( x.length, k, x, 1 );
+			if ( isnan( y[ i%x.length ] ) ) {
+				b.fail( 'should not return NaN' );
+			}
+		}
+		b.toc();
+		if ( isnan( y[ i%x.length ] ) ) {
+			b.fail( 'should not return NaN' );
+		}
+		b.pass( 'benchmark finished' );
+		b.end();
+	}
+}
+
+
+// MAIN //
+
+function main() {
+	var len;
+	var min;
+	var max;
+	var f;
+	var i;
+
+	min = 1; // 10^min
+	max = 6; // 10^max
+
+	for ( i = min; i <= max; i++ ) {
+		len = pow( 10, i );
+		f = createBenchmark( len );
+		bench( format( '%s:len=%d', pkg, len ), f );
+	}
+}
+
+main();