feat: add Node-API utility to convert a Node-API value to a signed 64-bit integer array

lib/node_modules/@stdlib/napi/argv-int64array/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.
+
+-->
+
+# argv_int64array
+
+> Convert a Node-API value to a signed 64-bit integer array.
+
+<!-- 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 -->
+
+<!-- Package usage documentation. -->
+
+<section class="usage">
+
+## Usage
+
+```javascript
+var headerDir = require( '@stdlib/napi/argv-int64array' );
+```
+
+#### headerDir
+
+Absolute file path for the directory containing header files for C APIs.
+
+```javascript
+var dir = headerDir;
+// returns <string>
+```
+
+</section>
+
+<!-- /.usage -->
+
+<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="notes">
+
+-   Node-API has no support for 64-bit integer typed arrays. Accordingly, a caller is expected to provide a `Uint32Array` containing interleaved high and low words in platform word order, as returned by [`@stdlib/strided/base/reinterpret-int64`][@stdlib/strided/base/reinterpret-int64]. The resolved array length is the number of 64-bit elements, which is half the number of words.
+
+</section>
+
+<!-- /.notes -->
+
+<!-- Package usage examples. -->
+
+<section class="examples">
+
+## Examples
+
+```javascript
+var headerDir = require( '@stdlib/napi/argv-int64array' );
+
+console.log( headerDir );
+// => <string>
+```
+
+</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/napi/argv_int64array.h"
+```
+
+#### stdlib_napi_argv_int64array( env, value, \*\*data, \*length, \*message, \*err )
+
+Converts a Node-API value to a signed 64-bit integer array.
+
+```c
+#include "stdlib/napi/argv_int64array.h"
+#include <node_api.h>
+#include <stdint.h>
+
+static napi_value addon( napi_env env, napi_callback_info info ) {
+    napi_value value;
+
+    // ...
+
+    int64_t *X;
+    int64_t len;
+    napi_value err;
+    napi_status status = stdlib_napi_argv_int64array( env, value, &X, &len, "Must be a typed array.", &err );
+    assert( status == napi_ok );
+    if ( err != NULL ) {
+        assert( napi_throw( env, err ) == napi_ok );
+        return NULL;
+    }
+
+    // ...
+}
+```
+
+The function accepts the following arguments:
+
+-   **env**: `[in] napi_env` environment under which the function is invoked.
+-   **value**: `[in] napi_value` Node-API value.
+-   **data**: `[out] int64_t**` pointer for returning a reference to the output array.
+-   **length**: `[out] int64_t*` pointer for returning the number of 64-bit array elements.
+-   **message**: `[in] char*` error message.
+-   **err**: `[out] napi_value*` pointer for storing a JavaScript error. If not provided a `Uint32Array`, the function sets `err` with a JavaScript error; otherwise, `err` is set to `NULL`.
+
+```c
+napi_status stdlib_napi_argv_int64array( const napi_env env, const napi_value value, int64_t **data, int64_t *length, const char *message, napi_value *err );
+```
+
+The function returns a `napi_status` status code indicating success or failure (returns `napi_ok` if success).
+
+#### STDLIB_NAPI_ARGV_INT64ARRAY( env, X, len, argv, index )
+
+Macro for converting an add-on callback argument to a signed 64-bit integer array.
+
+```c
+#include "stdlib/napi/argv_int64array.h"
+#include "stdlib/napi/argv.h"
+#include <node_api.h>
+#include <stdint.h>
+
+static void fcn( const int64_t *X, const int64_t xlen, int64_t *Y, const int64_t ylen ) {
+    int64_t len;
+    int64_t i;
+
+    if ( xlen > ylen ) {
+        len = ylen;
+    } else {
+        len = xlen;
+    }
+    for ( i = 0; i < len; i++ ) {
+        Y[ i ] = X[ i ];
+    }
+}
+
+// ...
+
+static napi_value addon( napi_env env, napi_callback_info info ) {
+    // Retrieve add-on callback arguments:
+    STDLIB_NAPI_ARGV( env, info, argv, argc, 2 );
+
+    // Convert the first argument to a C type:
+    STDLIB_NAPI_ARGV_INT64ARRAY( env, X, xlen, argv, 0 );
+
+    // Convert the second argument to a C type:
+    STDLIB_NAPI_ARGV_INT64ARRAY( env, Y, ylen, argv, 1 );
+
+    // ...
+
+    fcn( X, xlen, Y, ylen );
+}
+```
+
+The macro expects the following arguments:
+
+-   **env**: environment under which the callback is invoked.
+-   **X**: output variable name for the array.
+-   **len**: output variable name for the array length.
+-   **argv**: name of the variable containing add-on callback arguments.
+-   **index**: argument index.
+
+</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">
+
+</section>
+
+<!-- /.examples -->
+
+</section>
+
+<!-- /.c -->
+
+<!-- Section to include cited references. If references are included, add a horizontal rule *before* the section. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="references">
+
+</section>
+
+<!-- /.references -->
+
+<!-- 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/strided/base/reinterpret-int64]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/strided/base/reinterpret-int64
+
+</section>
+
+<!-- /.links -->