@stdlib/array
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Arrays.
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# fixedEndianFactory
> Return a typed array constructor for creating typed arrays having a specified byte order.
<!-- 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">
In contrast to built-in typed array constructors which store values according to the host platform byte order, the typed array constructors returned by the factory function allow enforcing a specific byte order. Such enforcement can be particularly advantageous when working with memory buffers which do not necessarily follow host platform byte order, such as [WebAssembly memory][@stdlib/wasm/memory].
</section>
<!-- /.intro -->
<!-- Package usage documentation. -->
<section class="usage">
## Usage
```javascript
var fixedEndianFactory = require( '@stdlib/array/fixed-endian-factory' );
```
#### fixedEndianFactory( dtype )
Returns a typed array constructor for creating typed arrays having a specified [data type][@stdlib/array/typed-dtypes] and byte order.
```javascript
var Float64ArrayFE = fixedEndianFactory( 'float64' );
// returns <Function>
var Float32ArrayFE = fixedEndianFactory( 'float32' );
// returns <Function>
```
* * *
### Typed Array Constructor
#### TypedArrayFE( endianness )
A typed array constructor which returns a typed array representing values stored in a specified byte order.
```javascript
var Float64ArrayFE = fixedEndianFactory( 'float64' );
var arr = new Float64ArrayFE( 'little-endian' );
// returns <Float64ArrayFE>
```
#### TypedArrayFE( endianness, length )
Returns a typed array having a specified length and byte order.
```javascript
var Float64ArrayFE = fixedEndianFactory( 'float64' );
var arr = new Float64ArrayFE( 'little-endian', 5 );
// returns <Float64ArrayFE>
```
#### TypedArrayFE( endianness, typedarray )
Creates a typed array from another typed array.
```javascript
var Float32Array = require( '@stdlib/array/float32' );
var Float64ArrayFE = fixedEndianFactory( 'float64' );
var arr1 = new Float32Array( [ 0.5, 0.5, 0.5 ] );
var arr2 = new Float64ArrayFE( 'little-endian', arr1 );
// returns <Float64ArrayFE>
var v = arr2.get( 0 );
// returns 0.5
```
#### TypedArrayFE( endianness, obj )
Creates a typed array from an array-like object or iterable.
```javascript
var Float64ArrayFE = fixedEndianFactory( 'float64' );
var arr = new Float64ArrayFE( 'little-endian', [ 0.5, 0.5, 0.5 ] );
// returns <Float64ArrayFE>
var v = arr.get( 0 );
// returns 0.5
```
#### TypedArrayFE( endianness, buffer\[, byteOffset\[, length]] )
Returns a typed array view of an [`ArrayBuffer`][@stdlib/array/buffer].
```javascript
var ArrayBuffer = require( '@stdlib/array/buffer' );
var Float64ArrayFE = fixedEndianFactory( 'float64' );
var buf = new ArrayBuffer( 32 );
var arr = new Float64ArrayFE( 'little-endian', buf, 0, 4 );
// returns <Float64ArrayFE>
```
* * *
### Typed Array Properties
<a name="static-prop-bytes-per-element"></a>
#### TypedArrayFE.BYTES_PER_ELEMENT
Number of bytes per view element.
```javascript
var Float64ArrayFE = fixedEndianFactory( 'float64' );
var nbytes = Float64ArrayFE.BYTES_PER_ELEMENT;
// returns 8
```
<a name="static-prop-name"></a>
#### TypedArrayFE.name
Typed array constructor name.
```javascript
var Float64ArrayFE = fixedEndianFactory( 'float64' );
var str = Float64ArrayFE.name;
// returns 'Float64ArrayFE'
```
<a name="prop-buffer"></a>
#### TypedArrayFE.prototype.buffer
**Read-only** property which returns the [`ArrayBuffer`][@stdlib/array/buffer] referenced by the typed array.
```javascript
var Float64ArrayFE = fixedEndianFactory( 'float64' );
var arr = new Float64ArrayFE( 'little-endian', 5 );
var buf = arr.buffer;
// returns <ArrayBuffer>
```
<a name="prop-byte-length"></a>
#### TypedArrayFE.prototype.byteLength
**Read-only** property which returns the length (in bytes) of the typed array.
```javascript
var Float64ArrayFE = fixedEndianFactory( 'float64' );
var arr = new Float64ArrayFE( 'little-endian', 5 );
var byteLength = arr.byteLength;
// returns 40
```
<a name="prop-byte-offset"></a>
#### TypedArrayFE.prototype.byteOffset
**Read-only** property which returns the offset (in bytes) of the typed array from the start of its [`ArrayBuffer`][@stdlib/array/buffer].
```javascript
var Float64ArrayFE = fixedEndianFactory( 'float64' );
var arr = new Float64ArrayFE( 'little-endian', 5 );
var byteOffset = arr.byteOffset;
// returns 0
```
<a name="prop-bytes-per-element"></a>
#### TypedArrayFE.prototype.BYTES_PER_ELEMENT
Number of bytes per view element.
```javascript
var Float64ArrayFE = fixedEndianFactory( 'float64' );
var arr = new Float64ArrayFE( 'little-endian', 5 );
var nbytes = arr.BYTES_PER_ELEMENT;
// returns 8
```
<a name="prop-length"></a>
#### TypedArrayFE.prototype.length
**Read-only** property which returns the number of view elements.
```javascript
var Float64ArrayFE = fixedEndianFactory( 'float64' );
var arr = new Float64ArrayFE( 'little-endian', 5 );
var len = arr.length;
// returns 5
```
* * *
### Typed Array Methods
<a name="static-method-from"></a>
#### TypedArrayFE.from( endianness, src\[, map\[, thisArg]] )
Creates a new typed array from an array-like object or an iterable.
```javascript
var Float64ArrayFE = fixedEndianFactory( 'float64' );
var arr = Float64ArrayFE.from( 'little-endian', [ 1.0, -1.0 ] );
// returns <Float64ArrayFE>
var v = arr.get( 0 );
// returns 1.0
```
To invoke a function for each `src` value, provide a callback function.
```javascript
function mapFcn( v ) {
return v * 2.0;
}
var Float64ArrayFE = fixedEndianFactory( 'float64' );
var arr = Float64ArrayFE.from( 'little-endian', [ 1.0, -1.0 ], mapFcn );
// returns <Float64ArrayFE>
var v = arr.get( 0 );
// returns 2.0
```
A callback function is provided two arguments:
- **value**: source value.
- **index**: source index.
To set the callback execution context, provide a `thisArg`.
```javascript
function mapFcn( v ) {
this.count += 1;
return v * 2.0;
}
var Float64ArrayFE = fixedEndianFactory( 'float64' );
var ctx = {
'count': 0
};
var arr = Float64ArrayFE.from( 'little-endian', [ 1.0, -1.0 ], mapFcn, ctx );
// returns <Float64ArrayFE>
var v = arr.get( 0 );
// returns 2.0
var n = ctx.count;
// returns 2
```
<a name="static-method-of"></a>
#### TypedArrayFE.of( endianness, element0\[, element1\[, ...elementN]] )
Creates a new typed array from a variable number of arguments.
```javascript
var Float64ArrayFE = fixedEndianFactory( 'float64' );
var arr = Float64ArrayFE.of( 'little-endian', 1.0, -1.0 );
// returns <Float64ArrayFE>
var v = arr.get( 0 );
// returns 1.0
```
<a name="method-get"></a>
#### TypedArrayFE.prototype.get( i )
Returns an array element located at a nonnegative integer position (index) `i`.
```javascript
var Float64ArrayFE = fixedEndianFactory( 'float64' );
var arr = new Float64ArrayFE( 'little-endian', 10 );
// Set the first element:
arr.set( 1.0, 0 );
// Get the first element:
var v = arr.get( 0 );
// returns 1.0
```
If provided an out-of-bounds index, the method returns `undefined`.
```javascript
var Float64ArrayFE = fixedEndianFactory( 'float64' );
var arr = new Float64ArrayFE( 'little-endian', 10 );
var v = arr.get( 100 );
// returns undefined
```
<a name="method-set"></a>
#### TypedArrayFE.prototype.set( arr\[, offset] )
Sets array elements.
```javascript
var Float64ArrayFE = fixedEndianFactory( 'float64' );
var arr = new Float64ArrayFE( 'little-endian', [ 1.0, 2.0, 3.0 ] );
// returns <Float64ArrayFE>
var v = arr.get( 0 );
// returns 1.0
v = arr.get( 1 );
// returns 2.0
// Set the first two array elements:
arr.set( [ 4.0, 5.0 ] );
v = arr.get( 0 );
// returns 4.0
v = arr.get( 1 );
// returns 5.0
```
By default, the method starts writing values at the first array index. To specify an alternative index, provide an index `offset`.
```javascript
var Float64ArrayFE = fixedEndianFactory( 'float64' );
var arr = new Float64ArrayFE( 'little-endian', [ 1.0, 2.0, 3.0 ] );
// returns <Float64ArrayFE>
// Set the last two array elements:
arr.set( [ 4.0, 5.0 ], 1 );
var v = arr.get( 1 );
// returns 4.0
v = arr.get( 2 );
// returns 5.0
```
A few notes:
- If `i` is out-of-bounds, the method throws an error.
- If a target array cannot accommodate all values (i.e., the length of source array plus `i` exceeds the target array length), the method throws an error.
- If provided a typed array which shares an [`ArrayBuffer`][@stdlib/array/buffer] with the target array, the method will intelligently copy the source range to the destination range.
<a name="method-to-string"></a>
#### TypedArrayFE.prototype.toString()
Serializes an array as a string.
```javascript
var Float64ArrayFE = fixedEndianFactory( 'float64' );
var arr = new Float64ArrayFE( 'little-endian', [ 1.0, 2.0, 3.0 ] );
var str = arr.toString();
// returns '1,2,3'
```
</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">
* * *
## Notes
- A returned constructor supports the following byte orders:
- **little-endian**: store values such that bytes are stored from least-to-most significant bytes. This is the dominant ordering for processor architectures and their associated memory. This is also the ordering for [WebAssembly memory][@stdlib/wasm/memory].
- **big-endian**: store values such that bytes are stored from most-to-least significant bytes. This is the dominant ordering in network protocols.
- While returned constructors _strive_ to maintain (but do not **guarantee**) consistency with [typed arrays][@stdlib/array/typed], significant deviations from ECMAScript-defined [typed array][@stdlib/array/typed] behavior are as follows:
- Constructors do **not** require the `new` operator.
- Accessing array elements using bracket syntax (e.g., `X[i]`) is **not** supported. Instead, one **must** use the `.get()` method.
</section>
<!-- /.notes -->
<!-- Package usage examples. -->
<section class="examples">
* * *
## Examples
<!-- eslint no-undef: "error" -->
```javascript
var Float64Array = require( '@stdlib/array/float64' );
var logEach = require( '@stdlib/console/log-each' );
var fixedEndianFactory = require( '@stdlib/array/fixed-endian-factory' );
var Float64ArrayFE = fixedEndianFactory( 'float64' );
// Create a typed array by specifying a length:
var out = new Float64ArrayFE( 'little-endian', 3 );
logEach( '%s', out );
// Create a typed array from an array:
var arr = [ 1.0, -1.0, -3.14, 3.14, 0.5, 0.5 ];
out = new Float64ArrayFE( 'big-endian', arr );
logEach( '%s', out );
// Create a typed array from an array buffer:
arr = new Float64Array( [ 1.0, -1.0, -3.14, 3.14, 0.5, 0.5 ] ); // host byte order
out = new Float64ArrayFE( 'little-endian', arr.buffer );
logEach( '%s', out );
// Create a typed array from an array buffer view:
arr = new Float64Array( [ 1.0, -1.0, -3.14, 3.14, 0.5, 0.5 ] ); // host byte order
out = new Float64ArrayFE( 'big-endian', arr.buffer, 8, 2 );
logEach( '%s', out );
```
</section>
<!-- /.examples -->
<!-- Section to include cited references. If references are included, add a horizontal rule *before* the section. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
<section class="references">
</section>
<!-- /.references -->
<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->
<section class="related">
</section>
<!-- /.related -->
<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
<section class="links">
[@stdlib/array/typed]: https://github.com/stdlib-js/array/tree/main/typed
[@stdlib/array/buffer]: https://github.com/stdlib-js/array/tree/main/buffer
[@stdlib/wasm/memory]: https://www.npmjs.com/package/@stdlib/wasm-memory
[@stdlib/array/typed-dtypes]: https://github.com/stdlib-js/array/tree/main/typed-dtypes
</section>
<!-- /.links -->