@stdlib/buffer-from-arraybuffer NPM

arraybuffer2buffer

Allocate a buffer from an ArrayBuffer.

Installation

npm install @stdlib/buffer-from-arraybuffer

Usage

var arraybuffer2buffer = require( '@stdlib/buffer-from-arraybuffer' );

arraybuffer2buffer( buf[, byteOffset[, length]] )

Allocates a buffer from an ArrayBuffer.

var ArrayBuffer = require( '@stdlib/array-buffer' );
var ab = new ArrayBuffer( 10 );

var buf = arraybuffer2buffer( ab );
// returns <Buffer>

By default, the function allocates a buffer starting from the first byte of the provided ArrayBuffer. To specify an alternative starting index, provide a byteOffset.

var ArrayBuffer = require( '@stdlib/array-buffer' );
var ab = new ArrayBuffer( 10 );

var buf = arraybuffer2buffer( ab, 2 );
// returns <Buffer>

var len = buf.length;
// returns 8

By default, the function allocates a buffer until the end of the provided ArrayBuffer. To allocate a specified number of ArrayBuffer bytes, provide a length.

var ArrayBuffer = require( '@stdlib/array-buffer' );
var ab = new ArrayBuffer( 10 );

var buf = arraybuffer2buffer( ab, 2, 4 );
// returns <Buffer>

var len = buf.length;
// returns 4

Notes

The behavior of this function varies across Node.js versions due to changes in the underlying Node.js APIs:

<3.0.0: the function copies ArrayBuffer bytes to a new Buffer instance.
>=3.0.0 and <5.10.0: if provided a byteOffset, the function copies ArrayBuffer bytes to a new Buffer instance; otherwise, the function returns a view of an ArrayBuffer without copying the underlying memory.
<6.0.0: if provided an empty ArrayBuffer, the function returns an empty Buffer which is not an ArrayBuffer view.
>=6.0.0: the function returns a view of an ArrayBuffer without copying the underlying memory.

Examples

var ArrayBuffer = require( '@stdlib/array-buffer' );
var Float64Array = require( '@stdlib/array-float64' );
var randu = require( '@stdlib/random-base-randu' );
var IS_LITTLE_ENDIAN = require( '@stdlib/assert-is-little-endian' );
var arraybuffer2buffer = require( '@stdlib/buffer-from-arraybuffer' );

var high;
var view;
var low;
var buf;
var ab;
var i;

// Allocate an ArrayBuffer:
ab = new ArrayBuffer( 64 );

// Create a Float64 view and set random values:
view = new Float64Array( ab );
for ( i = 0; i < view.length; i++ ) {
    view[ i ] = randu();
}

// Create a new buffer from the ArrayBuffer:
buf = arraybuffer2buffer( ab );

// Read the high and low words for each double:
for ( i = 0; i < view.length; i++ ) {
    if ( IS_LITTLE_ENDIAN ) {
        high = buf.readUInt32LE( (8*i)+4 );
        low = buf.readUInt32LE( 8*i );
    } else {
        high = buf.readUInt32BE( 8*i );
        low = buf.readUInt32BE( (8*i)+4 );
    }
    console.log( 'Value: %d. High: %d. Low: %d.', view[ i ], high, low );
}

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.