feat: add blas/ext/base/gcopy-within

lib/node_modules/@stdlib/blas/ext/base/gcopy-within/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.
+
+-->
+
+# gcopyWithin
+
+> Perform an in-place copy of elements within a strided array.
+
+<section class="usage">
+
+## Usage
+
+```javascript
+var gcopyWithin = require( '@stdlib/blas/ext/base/gcopy-within' );
+```
+
+#### gcopyWithin( N, target, start, end, x, strideX, workspace, strideW )
+
+Performs an in-place copy of elements within a strided array.
+
+```javascript
+var x = [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ];
+var w = [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ];
+
+gcopyWithin( x.length, 3, 1, 4, x, 1, w, 1 );
+// x => [ 1.0, 2.0, 3.0, 2.0, 3.0, 4.0 ]
+```
+
+The function has the following parameters:
+
+-   **N**: number of indexed elements.
+-   **target**: target index.
+-   **start**: source start index (inclusive).
+-   **end**: source end index (exclusive).
+-   **x**: input array-like object.
+-   **strideX**: stride length for `x`.
+-   **workspace**: workspace array. Must have at least `N` indexed elements.
+-   **strideW**: stride length for `workspace`.
+
+The `N` and stride parameters determine which elements in the strided array are accessed at runtime. For example, to copy every other element:
+
+```javascript
+var x = [ 1.0, 0.0, 3.0, 0.0, 5.0, 0.0, 7.0, 0.0 ];
+var w = [ 0.0, 0.0, 0.0 ];
+
+gcopyWithin( 3, 0, 1, 6, x, 2, w, 1 );
+// x => [ 3.0, 0.0, 5.0, 0.0, 5.0, 0.0, 7.0, 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( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
+
+// Create an offset view...
+var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
+
+// Create a workspace array...
+var w = new Float64Array( 6 );
+
+// Copy within the view...
+gcopyWithin( 6, 0, 3, 6, x1, 1, w, 1 );
+// x0 => <Float64Array>[ 1.0, 5.0, 6.0, 7.0, 5.0, 6.0, 7.0, 8.0 ]
+```
+
+<!-- lint disable maximum-heading-length -->
+
+#### gcopyWithin.ndarray( N, target, start, end, x, strideX, offsetX, workspace, strideW, offsetW )
+
+Performs an in-place copy of elements within a strided array using alternative indexing semantics.
+
+```javascript
+var x = [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ];
+var w = [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ];
+
+gcopyWithin.ndarray( x.length, 3, 1, 4, x, 1, 0, w, 1, 0 );
+// x => [ 1.0, 2.0, 3.0, 2.0, 3.0, 4.0 ]
+```
+
+The function has the following additional parameters:
+
+-   **offsetX**: starting index for `x`.
+-   **offsetW**: starting index for `workspace`.
+
+While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying buffer, the offset parameters support indexing semantics based on starting indices. For example, to copy elements starting from the third element:
+
+```javascript
+var x = [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ];
+var w = [ 0.0, 0.0, 0.0, 0.0 ];
+
+gcopyWithin.ndarray( 4, 2, 0, 2, x, 1, 2, w, 1, 0 );
+// x => [ 1.0, 2.0, 3.0, 4.0, 3.0, 4.0, 7.0, 8.0 ]
+```
+
+</section>
+
+<!-- /.usage -->
+
+<section class="notes">
+
+## Notes
+
+-   If `N <= 0`, both functions return the strided array unchanged.
+-   If `target >= N`, both functions return the strided array unchanged.
+-   If `start >= end`, both functions return the strided array unchanged.
+-   If the `start` and `target` index ranges do not overlap, the `workspace` array is unused and thus ignored.
+-   Both functions **mutate** the provided input strided array.
+-   Both functions support array-like objects having getter and setter accessors for array element access (e.g., [`@stdlib/array/base/accessor`][@stdlib/array/base/accessor]).
+-   Depending on the environment, the typed versions ([`dcopyWithin`][@stdlib/blas/ext/base/dcopy-within], [`scopyWithin`][@stdlib/blas/ext/base/scopy-within], etc.) are likely to be significantly more performant.
+
+</section>
+
+<!-- /.notes -->
+
+<section class="examples">
+
+## Examples
+
+<!-- eslint no-undef: "error" -->
+
+```javascript
+var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
+var zeros = require( '@stdlib/array/zeros' );
+var gcopyWithin = require( '@stdlib/blas/ext/base/gcopy-within' );
+
+var x = discreteUniform( 10, 0, 500, {
+    'dtype': 'generic'
+});
+console.log( x );
+
+var w = zeros( 10, 'generic' );
+
+// Copy the first 3 elements to positions 5, 6, 7:
+gcopyWithin( 10, 5, 0, 3, x, 1, w, 1 );
+console.log( x );
+```
+
+</section>
+
+<!-- /.examples -->
+
+<!-- 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">
+
+[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
+
+[@stdlib/array/base/accessor]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/base/accessor
+
+[@stdlib/blas/ext/base/dcopy-within]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/blas/ext/base/dcopy-within
+
+[@stdlib/blas/ext/base/scopy-within]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/blas/ext/base/scopy-within
+
+<!-- <related-links> -->
+
+<!-- </related-links> -->
+
+</section>
+
+<!-- /.links -->

lib/node_modules/@stdlib/blas/ext/base/gcopy-within/benchmark/benchmark.js

@@ -0,0 +1,108 @@
+/**
+* @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 zeros = require( '@stdlib/array/zeros' );
+var isnan = require( '@stdlib/math/base/assert/is-nan' );
+var pow = require( '@stdlib/math/base/special/pow' );
+var format = require( '@stdlib/string/format' );
+var gcopyWithin = require( './../lib/main.js' );
+var pkg = require( './../package.json' ).name;
+
+
+// VARIABLES //
+
+var options = {
+	'dtype': 'generic'
+};
+
+
+// FUNCTIONS //
+
+/**
+* Creates a benchmark function.
+*
+* @private
+* @param {PositiveInteger} len - array length
+* @returns {Function} benchmark function
+*/
+function createBenchmark( len ) {
+	var x;
+	var w;
+
+	x = uniform( len, -10.0, 10.0, options );
+	w = zeros( len, options.dtype );
+	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 = gcopyWithin( len, 0, 0, len - 1, x, 1, w, 1 );
+			if ( isnan( y[ i%y.length ] ) ) {
+				b.fail( 'should not return NaN' );
+			}
+		}
+		b.toc();
+		if ( isnan( x[ i%x.length ] ) ) {
+			b.fail( 'should not return NaN' );
+		}
+		b.pass( 'benchmark finished' );
+		b.end();
+	}
+}
+
+
+// MAIN //
+
+/**
+* Main execution sequence.
+*
+* @private
+*/
+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();