npm package: @stdlib/napi-argv-strided-float64array
Description: Convert a Node-API value representing a strided array to a double-precision floating-point array.
Author: The Stdlib Authors
Latest version: 0.2.3

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# argv_strided_float64array

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> Convert a Node-API value representing a strided array to a double-precision floating-point array.

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<section class="intro">

</section>

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<!-- Package usage documentation. -->

<section class="installation">

## Installation

```bash
npm install @stdlib/napi-argv-strided-float64array
```

</section>

<section class="usage">

## Usage

```javascript
var headerDir = require( '@stdlib/napi-argv-strided-float64array' );
```

#### headerDir

Absolute file path for the directory containing header files for C APIs.

```javascript
var dir = headerDir;
// returns <string>
```

</section>

<!-- /.usage -->

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<section class="notes">

</section>

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<section class="examples">

## Examples

```javascript
var headerDir = require( '@stdlib/napi-argv-strided-float64array' );

console.log( headerDir );
// => <string>
```

</section>

<!-- /.examples -->

<!-- C interface documentation. -->

* * *

<section class="c">

## C APIs

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<section class="intro">

</section>

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<section class="usage">

### Usage

```c
#include "stdlib/napi/argv_strided_float64array.h"
```

#### stdlib_napi_argv_strided_float64array( env, N, stride, value, \*\*data, \*message1, \*message2, \*err )

Converts a Node-API value representing a strided array to a double-precision floating-point array.

```c
#include "stdlib/napi/argv_strided_float64array.h"
#include <node_api.h>
#include <stdint.h>

static napi_value addon( napi_env env, napi_callback_info info ) {
    napi_value value;

    // ...

    int64_t N = 100;
    int64_t stride = 1;

    // ...

    double *X;
    napi_value err;
    napi_status status = stdlib_napi_argv_strided_float64array( env, N, stride, value, &X, "Must be a typed array.", "Must have sufficient elements.", &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.
-   **N**: `[in] int64_t` number of indexed elements.
-   **stride**: `[in] int64_t` stride length.
-   **value**: `[in] napi_value` Node-API value.
-   **data**: `[out] double**` pointer for returning a reference to the output array.
-   **message1**: `[in] char*` error message if a value is not a `Float64Array`.
-   **message2**: `[in] char*` error message if a value has insufficient elements.
-   **err**: `[out] napi_value*` pointer for storing a JavaScript error. If not provided a number, the function sets `err` with a JavaScript error; otherwise, `err` is set to `NULL`.

```c
napi_status stdlib_napi_argv_strided_float64array( const napi_env env, const int64_t N, const int64_t stride, const napi_value value, double **data, const char *message1, const char *message2, napi_value *err );
```

The function returns a `napi_status` status code indicating success or failure (returns `napi_ok` if success).

#### STDLIB_NAPI_ARGV_STRIDED_FLOAT64ARRAY( env, X, N, stride, argv, index )

Macro for converting an add-on callback argument to a strided double-precision floating-point array.

```c
#include "stdlib/napi/argv_strided_float64array.h"
#include "stdlib/napi_argv_int64.h"
#include "stdlib/napi/argv.h"
#include <node_api.h>
#include <stdint.h>

static void fcn( const int64_t N, const double *X, const int64_t strideX, double *Y, const int64_t strideY ) {
    int64_t i;
    for ( i = 0; i < N; i++ ) {
        Y[ i*strideY ] = X[ i*strideX ];
    }
}

// ...

static napi_value addon( napi_env env, napi_callback_info info ) {
    // Retrieve add-on callback arguments:
    STDLIB_NAPI_ARGV( env, info, argv, argc, 5 );

    // Convert the number of indexed elements to a C type:
    STDLIB_NAPI_ARGV_INT64( env, N, argv, 0 );

    // Convert the stride arguments to C types:
    STDLIB_NAPI_ARGV_INT64( env, strideX, argv, 2 );
    STDLIB_NAPI_ARGV_INT64( env, strideY, argv, 4 );

    // Convert the arrays a C types:
    STDLIB_NAPI_ARGV_STRIDED_FLOAT64ARRAY( env, X, N, strideX, argv, 1 );
    STDLIB_NAPI_ARGV_STRIDED_FLOAT64ARRAY( env, Y, N, strideY, argv, 3 );

    // ...

    fcn( N, X, strideX, Y, strideY );
}
```

The macro expects the following arguments:

-   **env**: environment under which the callback is invoked.
-   **X**: output variable name for the array.
-   **N**: number of indexed elements.
-   **stride**: stride length.
-   **argv**: name of the variable containing add-on callback arguments.
-   **index**: argument index.

</section>

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</section>

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<section class="examples">

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

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* * *

## Notice

This package is part of [stdlib][stdlib], a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop [stdlib][stdlib], see the main project [repository][stdlib].

#### Community

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---

## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

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