Package Exports

@stdlib/array-fixed-endian-float64
@stdlib/array-fixed-endian-float64/lib/index.js

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Float64ArrayFE

Typed array constructor which returns a typed array representing an array of double-precision floating-point numbers in a specified byte order.

In contrast to the Float64Array typed array constructor which stores values according to the host platform byte order, the Float64ArrayFE constructor allows 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.

Installation

npm install @stdlib/array-fixed-endian-float64

Usage

var Float64ArrayFE = require( '@stdlib/array-fixed-endian-float64' );

Float64ArrayFE( endianness )

A typed array constructor which returns a typed array representing an array of double-precision floating-point numbers in a specified byte order.

var arr = new Float64ArrayFE( 'little-endian' );
// returns <Float64ArrayFE>

Float64ArrayFE( endianness, length )

Returns a typed array having a specified length and byte order.

var arr = new Float64ArrayFE( 'little-endian', 5 );
// returns <Float64ArrayFE>

Float64ArrayFE( endianness, typedarray )

Creates a typed array from another typed array.

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

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

Float64ArrayFE( endianness, obj )

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

var arr = new Float64ArrayFE( 'little-endian', [ 0.5, 0.5, 0.5 ] );
// returns <Float64ArrayFE>

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

Float64ArrayFE( endianness, buffer[, byteOffset[, length]] )

Returns a typed array view of an ArrayBuffer.

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

var buf = new ArrayBuffer( 32 );
var arr = new Float64ArrayFE( 'little-endian', buf, 0, 4 );
// returns <Float64ArrayFE>

Properties

Float64ArrayFE.BYTES_PER_ELEMENT

Number of bytes per view element.

var nbytes = Float64ArrayFE.BYTES_PER_ELEMENT;
// returns 8

Float64ArrayFE.name

Typed array constructor name.

var str = Float64ArrayFE.name;
// returns 'Float64ArrayFE'

Float64ArrayFE.prototype.buffer

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

var arr = new Float64ArrayFE( 'little-endian', 5 );
var buf = arr.buffer;
// returns <ArrayBuffer>

Float64ArrayFE.prototype.byteLength

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

var arr = new Float64ArrayFE( 'little-endian', 5 );
var byteLength = arr.byteLength;
// returns 40

Float64ArrayFE.prototype.byteOffset

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

var arr = new Float64ArrayFE( 'little-endian', 5 );
var byteOffset = arr.byteOffset;
// returns 0

Float64ArrayFE.prototype.BYTES_PER_ELEMENT

Number of bytes per view element.

var arr = new Float64ArrayFE( 'little-endian', 5 );
var nbytes = arr.BYTES_PER_ELEMENT;
// returns 8

Float64ArrayFE.prototype.length

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

var arr = new Float64ArrayFE( 'little-endian', 5 );
var len = arr.length;
// returns 5

Methods

Float64ArrayFE.from( endianness, src[, map[, thisArg]] )

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

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.

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

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.

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

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

Float64ArrayFE.of( endianness, element0[, element1[, ...elementN]] )

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

var arr = Float64ArrayFE.of( 'little-endian', 1.0, -1.0 );
// returns <Float64ArrayFE>

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

Float64ArrayFE.prototype.get( i )

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

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.

var arr = new Float64ArrayFE( 'little-endian', 10 );

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

Float64ArrayFE.prototype.set( arr[, offset] )

Sets array elements.

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.

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

Float64ArrayFE.prototype.toString()

Serializes an array as a string.

var arr = new Float64ArrayFE( 'little-endian', [ 1.0, 2.0, 3.0 ] );

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

Notes

The 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.
- big-endian: store values such that bytes are stored from most-to-least significant bytes. This is the dominant ordering in network protocols.
While a Float64ArrayFE strives to maintain (but does not guarantee) consistency with typed arrays, significant deviations from ECMAScript-defined typed array behavior are as follows:
- The constructor does 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 Float64ArrayFE = require( '@stdlib/array-fixed-endian-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 );

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.

@stdlib/array-fixed-endian-float64