npm package: @stdlib/napi-argv-dataview
Description: Convert a Node-API value corresponding to a DataView to an array of bytes (i.e., an unsigned 8-bit integer array).
Author: The Stdlib Authors
Latest version: 0.1.1

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# argv_dataview

[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] <!-- [![dependencies][dependencies-image]][dependencies-url] -->

> Convert a Node-API value corresponding to a DataView to an array of bytes (i.e., an unsigned 8-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="installation">

## Installation

```bash
npm install @stdlib/napi-argv-dataview
```

</section>

<section class="usage">

## Usage

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

#### 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">

</section>

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<!-- Package usage examples. -->

<section class="examples">

## Examples

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

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

</section>

<!-- /.examples -->

<!-- C interface documentation. -->

* * *

<section class="c">

## C APIs

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<section class="intro">

</section>

<!-- /.intro -->

<!-- C usage documentation. -->

<section class="usage">

### Usage

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

#### stdlib_napi_argv_dataview( env, value, \*\*data, \*length, \*message, \*err )

Converts a Node-API value corresponding to a DataView to an array of bytes (i.e., an unsigned 8-bit integer array).

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

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

    // ...

    uint8_t *X;
    int64_t len;
    napi_value err;
    napi_status status = stdlib_napi_argv_dataview( env, value, &X, &len, "Must be a DataView.", &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] uint8_t**` pointer for returning a reference to the output array.
-   **length**: `[out] int64_t*` pointer for returning the number of array elements.
-   **message**: `[in] char*` error message.
-   **err**: `[out] napi_value*` pointer for storing a JavaScript error. If not provided a DataView, the function sets `err` with a JavaScript error; otherwise, `err` is set to `NULL`.

```c
napi_status stdlib_napi_argv_dataview( const napi_env env, const napi_value value, uint8_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_DATAVIEW( env, X, len, argv, index )

Macro for converting an add-on callback argument corresponding to a DataView to an array of bytes (i.e., an unsigned 8-bit integer array).

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

static void fcn( const uint8_t *X, const int64_t xlen, uint8_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_DATAVIEW( env, X, xlen, argv, 0 );

    // Convert the second argument to a C type:
    STDLIB_NAPI_ARGV_DATAVIEW( 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 -->

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<section class="examples">

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

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</section>

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<section class="main-repo" >

* * *

## 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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