@stdlib/napi/argv-uint32/README.md

C APIs for creating Node-API native add-ons.

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# argv_uint32

> Convert a Node-API value to an unsigned 32-bit integer.

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## Usage

```javascript
var headerDir = require( '@stdlib/napi/argv-uint32' );
```

#### headerDir

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

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

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## Examples

```javascript
var headerDir = require( '@stdlib/napi/argv-uint32' );

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

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* * *

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## C APIs

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### Usage

```c
#include "stdlib/napi/argv_uint32.h"
```

#### stdlib_napi_argv_uint32( env, value, \*out, \*message, \*err )

Converts a Node-API value to an unsigned 32-bit integer.

```c
#include "stdlib/napi/argv_uint32.h"
#include <node_api.h>
#include <stdint.h>

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

    // ...

    uint32_t out;
    napi_value err;
    napi_status status = stdlib_napi_argv_uint32( env, value, &out, "Must be a number.", &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.
-   **out**: `[out] uint32_t*` destination for storing output value.
-   **message**: `[in] char*` error message.
-   **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_uint32( const napi_env env, const napi_value value, uint32_t *out, 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_UINT32( env, name, argv, index )

Macro for converting an add-on callback argument to an unsigned 32-bit integer.

```c
#include "stdlib/napi/argv_uint32.h"
#include "stdlib/napi/argv.h"
#include <node_api.h>
#include <stdint.h>

static uint32_t fcn( const uint32_t v ) {
    return v;
}

// ...

static napi_value addon( napi_env env, napi_callback_info info ) {
    // Retrieve add-on callback arguments:
    STDLIB_NAPI_ARGV( env, info, argv, argc, 1 );

    // Convert the first argument to a C type:
    STDLIB_NAPI_ARGV_UINT32( env, value, argv, 0 );

    // ...

    uint32_t out = fcn( value );
}
```

The macro expects the following arguments:

-   **env**: environment under which the callback is invoked.
-   **name**: output variable name.
-   **argv**: name of the variable containing add-on callback arguments.
-   **index**: argument index.

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