feat: add blas/ext/base/smskrev

lib/node_modules/@stdlib/blas/ext/base/smskrev/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.
+
+-->
+
+# smskrev
+
+> Reverse a single-precision floating-point strided array in-place according to a mask.
+
+<section class="usage">
+
+## Usage
+
+```javascript
+var smskrev = require( '@stdlib/blas/ext/base/smskrev' );
+```
+
+#### smskrev( N, x, strideX, mask, strideMask )
+
+Reverses a single-precision floating-point strided array in-place according to a mask.
+
+```javascript
+var Float32Array = require( '@stdlib/array/float32' );
+var Uint8Array = require( '@stdlib/array/uint8' );
+
+var x = new Float32Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );
+var mask = new Uint8Array( [ 0, 0, 0, 1, 0, 0, 0, 0 ] );
+
+smskrev( x.length, x, 1, mask, 1 );
+// x => <Float32Array>[ -3.0, -1.0, 0.0, -5.0, 4.0, 3.0, 1.0, -2.0 ]
+```
+
+The function has the following parameters:
+
+-   **N**: number of indexed elements.
+-   **x**: input [`Float32Array`][@stdlib/array/float32].
+-   **strideX**: stride length for `x`.
+-   **mask**: mask [`Uint8Array`][@stdlib/array/uint8]. If a `mask` array element is `0`, the corresponding element in `x` is considered valid and **included** in the reversal. If a `mask` array element is `1`, the corresponding element in `x` is considered invalid/missing and **excluded** from the reversal.
+-   **strideMask**: stride length for `mask`.
+
+The `N` and stride parameters determine which elements in the strided arrays are accessed at runtime. For example, to reverse every other element:
+
+```javascript
+var Float32Array = require( '@stdlib/array/float32' );
+var Uint8Array = require( '@stdlib/array/uint8' );
+
+var x = new Float32Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );
+var mask = new Uint8Array( [ 0, 0, 0, 0 ] );
+
+smskrev( 4, x, 2, mask, 1 );
+// x => <Float32Array>[ -1.0, 1.0, 4.0, -5.0, 3.0, 0.0, -2.0, -3.0 ]
+```
+
+Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.
+
+```javascript
+var Float32Array = require( '@stdlib/array/float32' );
+var Uint8Array = require( '@stdlib/array/uint8' );
+
+// Initial arrays...
+var x0 = new Float32Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ] );
+var m0 = new Uint8Array( [ 0, 0, 0, 0, 0, 0 ] );
+
+// Create offset views...
+var x1 = new Float32Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
+var m1 = new Uint8Array( m0.buffer, m0.BYTES_PER_ELEMENT*1 );
+
+// Reverse every other element...
+smskrev( 3, x1, 2, m1, 1 );
+// x0 => <Float32Array>[ 1.0, -6.0, 3.0, -4.0, 5.0, -2.0 ]
+```
+
+#### smskrev.ndarray( N, x, strideX, offsetX, mask, strideMask, offsetMask )
+
+Reverses a single-precision floating-point strided array in-place according to a mask and using alternative indexing semantics.
+
+```javascript
+var Float32Array = require( '@stdlib/array/float32' );
+var Uint8Array = require( '@stdlib/array/uint8' );
+
+var x = new Float32Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );
+var mask = new Uint8Array( [ 0, 0, 0, 1, 0, 0, 0, 0 ] );
+
+smskrev.ndarray( x.length, x, 1, 0, mask, 1, 0 );
+// x => <Float32Array>[ -3.0, -1.0, 0.0, -5.0, 4.0, 3.0, 1.0, -2.0 ]
+```
+
+The function has the following additional parameters:
+
+-   **offsetX**: starting index for `x`.
+-   **offsetMask**: starting index for `mask`.
+
+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 access only the last three elements:
+
+```javascript
+var Float32Array = require( '@stdlib/array/float32' );
+var Uint8Array = require( '@stdlib/array/uint8' );
+
+var x = new Float32Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ] );
+var mask = new Uint8Array( [ 0, 0, 0, 0, 0, 0 ] );
+
+smskrev.ndarray( 3, x, 1, x.length-3, mask, 1, 3 );
+// x => <Float32Array>[ 1.0, -2.0, 3.0, -6.0, 5.0, -4.0 ]
+```
+
+</section>
+
+<!-- /.usage -->
+
+<section class="notes">
+
+## Notes
+
+-   If `N <= 0`, both functions return `x` unchanged.
+-   Where possible, one should "reverse" a strided array by negating its stride, which is an `O(1)` operation, in contrast to performing an in-place reversal, which is `O(N)`. However, in certain circumstances, this is not tenable, particularly when interfacing with libraries which assume and/or expect a specific memory layout (e.g., strided array elements arranged in memory in ascending order). In general, when working with strided arrays, only perform an in-place reversal when strictly necessary.
+
+</section>
+
+<!-- /.notes -->
+
+<section class="examples">
+
+## Examples
+
+<!-- eslint no-undef: "error" -->
+
+```javascript
+var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
+var Uint8Array = require( '@stdlib/array/uint8' );
+var smskrev = require( '@stdlib/blas/ext/base/smskrev' );
+
+var x = discreteUniform( 10, -100, 100, {
+    'dtype': 'float32'
+});
+console.log( x );
+
+var mask = new Uint8Array( [ 0, 0, 0, 1, 0, 0, 1, 0, 0, 0 ] );
+console.log( mask );
+
+smskrev( x.length, x, 1, mask, 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/smskrev.h"
+```
+
+#### stdlib_strided_smskrev( N, \*X, strideX, \*Mask, strideMask )
+
+Reverses a single-precision floating-point strided array in-place according to a mask.
+
+```c
+#include <stdint.h>
+
+float x[] = { 1.0f, 2.0f, 3.0f, 4.0f };
+const uint8_t mask[] = { 0, 0, 0, 0 };
+
+stdlib_strided_smskrev( 4, x, 1, mask, 1 );
+```
+
+The function accepts the following arguments:
+
+-   **N**: `[in] CBLAS_INT` number of indexed elements.
+-   **X**: `[inout] float*` input array.
+-   **strideX**: `[in] CBLAS_INT` stride length for `X`.
+-   **Mask**: `[in] uint8_t*` mask array.
+-   **strideMask**: `[in] CBLAS_INT` stride length for `Mask`.
+
+```c
+void stdlib_strided_smskrev( const CBLAS_INT N, float *X, const CBLAS_INT strideX, const uint8_t *Mask, const CBLAS_INT strideMask );
+```
+
+<!-- lint disable maximum-heading-length -->
+
+#### stdlib_strided_smskrev_ndarray( N, \*X, strideX, offsetX, \*Mask, strideMask, offsetMask )
+
+<!-- lint enable maximum-heading-length -->
+
+Reverses a single-precision floating-point strided array in-place according to a mask and using alternative indexing semantics.
+
+```c
+#include <stdint.h>
+
+float x[] = { 1.0f, 2.0f, 3.0f, 4.0f };
+const uint8_t mask[] = { 0, 0, 0, 0 };
+
+stdlib_strided_smskrev_ndarray( 4, x, 1, 0, mask, 1, 0 );
+```
+
+The function accepts the following arguments:
+
+-   **N**: `[in] CBLAS_INT` number of indexed elements.
+-   **X**: `[inout] float*` input array.
+-   **strideX**: `[in] CBLAS_INT` stride length for `X`.
+-   **offsetX**: `[in] CBLAS_INT` starting index for `X`.
+-   **Mask**: `[in] uint8_t*` mask array.
+-   **strideMask**: `[in] CBLAS_INT` stride length for `Mask`.
+-   **offsetMask**: `[in] CBLAS_INT` starting index for `Mask`.
+
+```c
+void stdlib_strided_smskrev_ndarray( const CBLAS_INT N, float *X, const CBLAS_INT strideX, const CBLAS_INT offsetX, const uint8_t *Mask, const CBLAS_INT strideMask, const CBLAS_INT offsetMask );
+```
+
+</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/smskrev.h"
+#include <stdint.h>
+#include <stdio.h>
+
+int main( void ) {
+    // Create a strided array:
+    float x[] = { 1.0f, -2.0f, 3.0f, -4.0f, 5.0f, -6.0f, 7.0f, -8.0f };
+
+    // Create a mask array:
+    const uint8_t mask[] = { 0, 0, 0, 1, 0, 0, 0, 0 };
+
+    // Specify the number of elements:
+    const int N = 8;
+
+    // Specify strides:
+    const int strideX = 1;
+    const int strideMask = 1;
+
+    // Reverse the array:
+    stdlib_strided_smskrev( N, x, strideX, mask, strideMask );
+
+    // Print the result:
+    for ( int i = 0; i < 8; i++ ) {
+        printf( "x[ %i ] = %f\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/float32]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/float32
+
+[@stdlib/array/uint8]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/uint8
+
+[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
+
+<!-- <related-links> -->
+
+<!-- </related-links> -->
+
+</section>
+
+<!-- /.links -->