@stdlib/array-little-endian-factory

v0.1.1

Published

a day ago

Return a typed array constructor for creating typed arrays stored in little-endian byte order.

littleEndianFactory

Return a typed array constructor for creating typed arrays stored in little-endian byte order.

In contrast to the built-in typed array constructors which store values according to the host platform byte order, the typed array constructors returned by the factory function always access elements in little-endian 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.

Installation

npm install @stdlib/array-little-endian-factory

Usage

var littleEndianFactory = require( '@stdlib/array-little-endian-factory' );

littleEndianFactory( dtype )

Returns a typed array constructor for creating typed arrays having a specified data type and stored in little-endian byte order.

var Float64ArrayLE = littleEndianFactory( 'float64' );
// returns <Function>

var Float32ArrayLE = littleEndianFactory( 'float32' );
// returns <Function>

Typed Array Constructor

TypedArrayLE()

A typed array constructor which returns a typed array representing an array of values in little-endian byte order.

var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE();
// returns <Float64ArrayLE>

TypedArrayLE( length )

Returns a typed array having a specified length.

var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE( 5 );
// returns <Float64ArrayLE>

TypedArrayLE( typedarray )

Creates a typed array from another typed array.

var Float32Array = require( '@stdlib/array-float32' );

var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr1 = new Float32Array( [ 0.5, 0.5, 0.5 ] );
var arr2 = new Float64ArrayLE( arr1 );
// returns <Float64ArrayLE>

var v = arr2.get( 0 );
// returns 0.5

TypedArrayLE( obj )

Creates a typed array from an array-like object or iterable.

var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE( [ 0.5, 0.5, 0.5 ] );
// returns <Float64ArrayLE>

var v = arr.get( 0 );
// returns 0.5

TypedArrayLE( buffer[, byteOffset[, length]] )

Returns a typed array view of an ArrayBuffer.

var ArrayBuffer = require( '@stdlib/array-buffer' );

var Float64ArrayLE = littleEndianFactory( 'float64' );

var buf = new ArrayBuffer( 32 );
var arr = new Float64ArrayLE( buf, 0, 4 );
// returns <Float64ArrayLE>

Typed Array Properties

TypedArrayLE.BYTES_PER_ELEMENT

Number of bytes per view element.

var Float64ArrayLE = littleEndianFactory( 'float64' );

var nbytes = Float64ArrayLE.BYTES_PER_ELEMENT;
// returns 8

TypedArrayLE.name

Typed array constructor name.

var Float64ArrayLE = littleEndianFactory( 'float64' );

var str = Float64ArrayLE.name;
// returns 'Float64ArrayLE'

TypedArrayLE.prototype.buffer

Read-only property which returns the ArrayBuffer referenced by the typed array.

var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE( 5 );
var buf = arr.buffer;
// returns <ArrayBuffer>

TypedArrayLE.prototype.byteLength

Read-only property which returns the length (in bytes) of the typed array.

var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE( 5 );
var byteLength = arr.byteLength;
// returns 40

TypedArrayLE.prototype.byteOffset

Read-only property which returns the offset (in bytes) of the typed array from the start of its ArrayBuffer.

var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE( 5 );
var byteOffset = arr.byteOffset;
// returns 0

TypedArrayLE.prototype.BYTES_PER_ELEMENT

Number of bytes per view element.

var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE( 5 );
var nbytes = arr.BYTES_PER_ELEMENT;
// returns 8

TypedArrayLE.prototype.length

Read-only property which returns the number of view elements.

var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE( 5 );
var len = arr.length;
// returns 5

Typed Array Methods

TypedArrayLE.from( src[, map[, thisArg]] )

Creates a new typed array from an array-like object or an iterable.

var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = Float64ArrayLE.from( [ 1.0, -1.0 ] );
// returns <Float64ArrayLE>

var v = arr.get( 0 );
// returns 1.0

To invoke a function for each src value, provide a callback function.

function mapFcn( v ) {
    return v * 2.0;
}

var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = Float64ArrayLE.from( [ 1.0, -1.0 ], mapFcn );
// returns <Float64ArrayLE>

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.

function mapFcn( v ) {
    this.count += 1;
    return v * 2.0;
}

var Float64ArrayLE = littleEndianFactory( 'float64' );

var ctx = {
    'count': 0
};

var arr = Float64ArrayLE.from( [ 1.0, -1.0 ], mapFcn, ctx );
// returns <Float64ArrayLE>

var v = arr.get( 0 );
// returns 2.0

var n = ctx.count;
// returns 2

TypedArrayLE.of( element0[, element1[, ...elementN]] )

Creates a new typed array from a variable number of arguments.

var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = Float64ArrayLE.of( 1.0, -1.0 );
// returns <Float64ArrayLE>

var v = arr.get( 0 );
// returns 1.0

TypedArrayLE.prototype.get( i )

Returns an array element located at a nonnegative integer position (index) i.

var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE( 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.

var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE( 10 );

var v = arr.get( 100 );
// returns undefined

TypedArrayLE.prototype.set( arr[, offset] )

Sets array elements.

var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE( [ 1.0, 2.0, 3.0 ] );
// returns <Float64ArrayLE>

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.

var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE( [ 1.0, 2.0, 3.0 ] );
// returns <Float64ArrayLE>

// 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 with the target array, the method will intelligently copy the source range to the destination range.

TypedArrayLE.prototype.toString()

Serializes an array as a string.

var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE( [ 1.0, 2.0, 3.0 ] );

var str = arr.toString();
// returns '1,2,3'

Notes

While returned constructors strive to maintain (but do not guarantee) consistency with typed arrays, significant deviations from ECMAScript-defined typed array behavior are as follows:
- Constructors 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.

Examples

var Float64Array = require( '@stdlib/array-float64' );
var logEach = require( '@stdlib/console-log-each' );
var littleEndianFactory = require( '@stdlib/array-little-endian-factory' );

var Float64ArrayLE = littleEndianFactory( 'float64' );

// Create a typed array by specifying a length:
var out = new Float64ArrayLE( 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 Float64ArrayLE( 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 Float64ArrayLE( 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 Float64ArrayLE( arr.buffer, 8, 2 );
logEach( '%s', out );

Notice

This package is part of 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, see the main project repository.

Community

License

See LICENSE.