@stdlib/napi/argv-strided-uint16array/README.md

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

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# argv_strided_uint16array

> Convert a Node-API value representing a strided array to an unsigned 16-bit integer array.

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## Usage

```javascript
var headerDir = require( '@stdlib/napi/argv-strided-uint16array' );
```

#### 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-strided-uint16array' );

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

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* * *

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## C APIs

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### Usage

```c
#include "stdlib/napi/argv_strided_uint16array.h"
```

#### stdlib_napi_argv_strided_uint16array( env, N, stride, value, \*\*data, \*message1, \*message2, \*err )

Converts a Node-API value representing a strided array to an unsigned 16-bit integer array.

```c
#include "stdlib/napi/argv_strided_uint16array.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;

    // ...

    uint16_t *X;
    napi_value err;
    napi_status status = stdlib_napi_argv_strided_uint16array( 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] uint16_t**` pointer for returning a reference to the output array.
-   **message1**: `[in] char*` error message if a value is not a `Uint16Array`.
-   **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_uint16array( const napi_env env, const int64_t N, const int64_t stride, const napi_value value, uint16_t **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_UINT16ARRAY( env, X, N, stride, argv, index )

Macro for converting an add-on callback argument to a strided unsigned 16-bit integer array.

```c
#include "stdlib/napi/argv_strided_uint16array.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 uint16_t *X, const int64_t strideX, uint16_t *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_UINT16ARRAY( env, X, N, strideX, argv, 1 );
    STDLIB_NAPI_ARGV_STRIDED_UINT16ARRAY( 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.

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