@stdlib/strided/base/write-dataview/README.md

Strided.

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# writeDataView

> Copy elements from an input strided array to elements in a strided [`DataView`][@stdlib/array/dataview].

<section class="intro">

</section>

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<section class="usage">

## Usage

```javascript
var writeDataView = require( '@stdlib/strided/base/write-dataview' );
```

#### writeDataView( N, x, strideX, view, strideView, littleEndian )

Copies elements from an input strided array to elements in a strided [`DataView`][@stdlib/array/dataview].

```javascript
var ArrayBuffer = require( '@stdlib/array/buffer' );
var DataView = require( '@stdlib/array/dataview' );

var x = [ 1.0, 2.0, 3.0, 4.0 ];

var buf = new ArrayBuffer( 32 );
var view = new DataView( buf );

var out = writeDataView( 4, x, 1, view, 8, true );
// returns <DataView>

var bool = ( out === view );
// returns true

var v = view.getFloat64( 0, true );
// returns 1.0

v = view.getFloat64( 8, true );
// returns 2.0
```

The function accepts the following arguments:

-   **N**: number of indexed elements.
-   **x**: input strided array.
-   **strideX**: index increment for `x`.
-   **view**: output [`DataView`][@stdlib/array/dataview].
-   **strideView**: index increment (in bytes) for `view`.
-   **littleEndian**: boolean indicating whether to store values in little-endian format.

The `N` and stride parameters determine which elements in `x` and `view` are accessed at runtime. For example, to index every other value in `x` and to index the first `N` elements of `view` in reverse order,

```javascript
var ArrayBuffer = require( '@stdlib/array/buffer' );
var DataView = require( '@stdlib/array/dataview' );

var x = [ 1.0, 0.0, 2.0, 0.0, 3.0, 0.0, 4.0, 0.0 ];

var buf = new ArrayBuffer( 64 );
var view = new DataView( buf );

var out = writeDataView( 4, x, 2, view, -8, true );
// returns <DataView>

var bool = ( out === view );
// returns true

var v = view.getFloat64( 0, true );
// returns 4.0

v = view.getFloat64( 8, true );
// returns 3.0
```

Note that indexing is relative to the first index. To introduce an offset, use typed array views.

```javascript
var ArrayBuffer = require( '@stdlib/array/buffer' );
var DataView = require( '@stdlib/array/dataview' );
var Float32Array = require( '@stdlib/array/float32' );

// Initial array:
var x0 = new Float32Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );

// Create an offset view:
var x1 = new Float32Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

// Create an output DataView:
var buf = new ArrayBuffer( 64 );
var view = new DataView( buf );

var out = writeDataView( 4, x1, 1, view, 8, true );
// returns <DataView>

var bool = ( out === view );
// returns true

var v = view.getFloat32( 0, true );
// returns 2.0

v = view.getFloat32( 8, true );
// returns 3.0
```

#### writeDataView.ndarray( N, x, strideX, offsetX, view, strideView, offsetView, littleEndian )

Copies elements from an input strided array to elements in a strided [`DataView`][@stdlib/array/dataview] using alternative indexing semantics.

```javascript
var ArrayBuffer = require( '@stdlib/array/buffer' );
var DataView = require( '@stdlib/array/dataview' );

var x = [ 1.0, 2.0, 3.0, 4.0 ];

var buf = new ArrayBuffer( 32 );
var view = new DataView( buf );

var out = writeDataView.ndarray( 4, x, 1, 0, view, 8, 0, true );
// returns <DataView>

var bool = ( out === view );
// returns true

var v = view.getFloat64( 0, true );
// returns 1.0
```

The function accepts the following additional arguments:

-   **offsetX**: starting index for `x`.
-   **offsetView**: starting index (in bytes) for `view`.

While typed array views mandate a view offset based on the underlying buffer, the offset parameters support indexing semantics based on starting indices. For example, to index every other value in `x` starting from the second value and to index the last `N` elements in `view` in reverse order,

```javascript
var ArrayBuffer = require( '@stdlib/array/buffer' );
var DataView = require( '@stdlib/array/dataview' );

var x = [ 0.0, 1.0, 0.0, 2.0, 0.0, 3.0, 0.0, 4.0 ];

var buf = new ArrayBuffer( 64 );
var view = new DataView( buf );

var out = writeDataView.ndarray( 4, x, 2, 1, view, -8, 56, true );
// returns <DataView>

var bool = ( out === view );
// returns true

var v = view.getFloat64( 32, true );
// returns 4.0

v = view.getFloat64( 40, true );
// returns 3.0
```

</section>

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<section class="notes">

</section>

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<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var ArrayBuffer = require( '@stdlib/array/buffer' );
var DataView = require( '@stdlib/array/dataview' );
var typedarray = require( '@stdlib/array/typed' );
var bytesPerElement = require( '@stdlib/ndarray/base/bytes-per-element' );
var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var IS_LITTLE_ENDIAN = require( '@stdlib/assert/is-little-endian' );
var logEach = require( '@stdlib/console/log-each' );
var writeDataView = require( '@stdlib/strided/base/write-dataview' );

// Specify the array data type:
var dtype = 'float64';

// Resolve the number of bytes per element:
var nbytes = bytesPerElement( dtype );

// Generate an array of random numbers:
var x = discreteUniform( 10, 0, 100, {
    'dtype': dtype
});

// Create a DataView:
var buf = new ArrayBuffer( x.length*nbytes );
var view = new DataView( buf );

// Copy the numbers to the DataView:
writeDataView( x.length, x, 1, view, nbytes, IS_LITTLE_ENDIAN );

// Create a view of the DataView:
var y = typedarray( view.buffer, dtype );

// Print the results:
logEach( '%d -> %d', x, y );
```

</section>

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</section>

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<section class="links">

[@stdlib/array/dataview]: https://www.npmjs.com/package/@stdlib/array-dataview

</section>

<!-- /.links -->