time-to-botec/js/node_modules/@stdlib/buffer/from-arraybuffer

arraybuffer2buffer

Allocate a buffer from an 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 );
}