readDataView

Usage

var readDataView = require( '@stdlib/strided/base/read-dataview' );

readDataView( N, view, strideView, out, strideOut, littleEndian )

Copies elements from an input strided DataView to elements in an output strided array.

var Float64Array = require( '@stdlib/array/float64' );
var DataView = require( '@stdlib/array/dataview' );

var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0 ] );
var view = new DataView( x.buffer );

var y = new Float64Array( x.length );
var out = readDataView( x.length, view, 8, y, 1, true );
// e.g., returns <Float64Array>[ 1.0, 2.0, 3.0, 4.0 ]

var bool = ( out === y );
// returns true

The function accepts the following arguments:

• N: number of indexed elements.
• view: input DataView.
• strideView: index increment (in bytes) for view.
• out: output strided array.
• strideOut: index increment for out.
• littleEndian: boolean indicating whether to store values in little-endian format.

The N and stride parameters determine which elements in view and out are accessed at runtime. For example, to index the first N elements of view in reverse order and to index every other value in out ,

var Float64Array = require( '@stdlib/array/float64' );
var DataView = require( '@stdlib/array/dataview' );

var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0 ] );
var view = new DataView( x.buffer );

var y = new Float64Array( x.length*2 );
var out = readDataView( x.length, view, -8, y, 2, true );
// e.g., returns <Float64Array>[ 4.0, 0.0, 3.0, 0.0, 2.0, 0.0, 1.0, 0.0 ]

var bool = ( out === y );
// returns true

Note that indexing is relative to the first index. To introduce an offset, use typed array views.

var Float64Array = require( '@stdlib/array/float64' );
var DataView = require( '@stdlib/array/dataview' );

var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0 ] );
var view = new DataView( x.buffer );

// Initial output array:
var y0 = new Float64Array( x.length+1 );

// Create an offset view:
var y1 = new Float64Array( y0.buffer, y0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

var out = readDataView( x.length, view, 8, y1, 1, true );
// e.g., returns <Float64Array>[ 1.0, 2.0, 3.0, 4.0 ]

var bool = ( out === y1 );
// returns true

readDataView.ndarray( N, view, strideView, offsetView, out, strideOut, offsetOut, littleEndian )

Copies elements from an input strided DataView to elements in an output strided array using alternative indexing semantics.

var Float64Array = require( '@stdlib/array/float64' );
var DataView = require( '@stdlib/array/dataview' );

var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0 ] );
var view = new DataView( x.buffer );

var y = new Float64Array( x.length );
var out = readDataView.ndarray( x.length, view, 8, 0, y, 1, 0, true );
// e.g., returns <Float64Array>[ 1.0, 2.0, 3.0, 4.0 ]

var bool = ( out === y );
// returns true

The function accepts the following additional arguments:

• offsetView: starting index (in bytes) for view.
• offsetOut: starting index for out.

While typed array views mandate a view offset based on the underlying buffer, the offset parameters support indexing semantics based on starting indices. For example, to index the last N elements in view in reverse order and to index every other value in out starting from the second value,

var Float64Array = require( '@stdlib/array/float64' );
var DataView = require( '@stdlib/array/dataview' );

var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0 ] );
var view = new DataView( x.buffer );

var y = new Float64Array( x.length*2 );
var out = readDataView.ndarray( x.length, view, -8, 24, y, 2, 1, true );
// e.g., returns <Float64Array>[ 0.0, 4.0, 0.0, 3.0, 0.0, 2.0, 0.0, 1.0 ]

var bool = ( out === y );
// returns true