@stdlib/streams-node-from-circular-array NPM

Circular Array Stream

Create a readable stream from a circular array-like object.

Installation

npm install @stdlib/streams-node-from-circular-array

Usage

var circularArrayStream = require( '@stdlib/streams-node-from-circular-array' );

circularArrayStream( src[, options] )

Returns a readable stream from an array-like object which repeatedly iterates over a provided value's elements.

var inspectStream = require( '@stdlib/streams-node-inspect-sink' );

var iStream;
var stream;
var count;

function log( chunk ) {
    console.log( chunk.toString() );
    count += 1;
    if ( count === 20 ) {
        stream.destroy();
    }
}

stream = circularArrayStream( [ 1, 2, 3, 4 ] );
iStream = inspectStream( log );

count = 0;
stream.pipe( iStream );

The function accepts the following options:

objectMode: specifies whether a stream should operate in objectMode. Default: false.
encoding: specifies how Buffer objects should be decoded to strings. Default: null.
highWaterMark: specifies the maximum number of bytes to store in an internal buffer before pausing streaming.
sep: separator used to join streamed data. This option is only applicable when a stream is not in objectMode. Default: '\n'.
serialize: custom serialization function. This option is only applicable when a stream is not in objectMode.
iter: number of iterations. Default: 1e308.
dir: iteration direction. If set to -1, the stream iterates over elements from right-to-left. Default: 1.

To set stream options,

var opts = {
    'objectMode': true,
    'encoding': 'utf8',
    'highWaterMark': 64
};

var stream = circularArrayStream( [ 1, 2, 3, 4 ], opts );

By default, the returned stream is an infinite stream (i.e., never ends). To limit the number of streamed values, set the iter option.

var inspectStream = require( '@stdlib/streams-node-inspect-sink' );

function log( chunk ) {
    console.log( chunk.toString() );
}

var opts = {
    'iter': 10
};
var stream = circularArrayStream( [ 1, 2, 3, 4 ], opts );
var iStream = inspectStream( log );

stream.pipe( iStream );

By default, when not operating in objectMode, a returned stream delineates individual values using a newline character. To specify an alternative separator, set the sep option.

var inspectStream = require( '@stdlib/streams-node-inspect-sink' );

function log( chunk ) {
    console.log( chunk.toString() );
}

var stream = circularArrayStream( [ 1, 2, 3, 4 ], {
    'sep': ',',
    'iter': 10
});

var iStream = inspectStream( log );

stream.pipe( iStream );

By default, when not operating in objectMode, a returned stream serializes values as JSON strings. To specify custom serialization behavior (either to a string or Buffer), set the serialize option.

var inspectStream = require( '@stdlib/streams-node-inspect-sink' );

function serialize( v ) {
    return 'v::' + v.toString();
}

function log( chunk ) {
    console.log( chunk.toString() );
}

var stream = circularArrayStream( [ 1, 2, 3, 4 ], {
    'serialize': serialize,
    'iter': 10
});

var iStream = inspectStream( log );

stream.pipe( iStream );

circularArrayStream.factory( [options] )

Returns a function for creating readable streams from array-like objects.

var opts = {
    'objectMode': true,
    'encoding': 'utf8',
    'highWaterMark': 64
};

var createStream = circularArrayStream.factory( opts );

var stream1 = createStream( [ 1, 2, 3, 4 ] );
var stream2 = createStream( [ 5, 6, 7, 8 ] );
// ...

The method accepts the same options as circularArrayStream().

circularArrayStream.objectMode( src[, options] )

This method is a convenience function to create streams which always operate in objectMode.

var inspectStream = require( '@stdlib/streams-node-inspect-sink' );

function log( v ) {
    console.log( v );
}

var opts = {
    'iter': 10
};
var stream = circularArrayStream.objectMode( [ 1, 2, 3, 4 ], opts );

opts = {
    'objectMode': true
};
var iStream = inspectStream( opts, log );

stream.pipe( iStream );

This method accepts the same options as circularArrayStream(); however, the method will always override the objectMode option in options.

Notes

In objectMode, null is a reserved value. If an array contains null values (e.g., as a means to encode missing values), the stream will prematurely end. Consider an alternative encoding or filter null values prior to invocation.
In binary mode, if an array contains undefined values, the stream will emit an error. Consider providing a custom serialization function or filtering undefined values prior to invocation.

Examples

var inspectStream = require( '@stdlib/streams-node-inspect-sink' );
var randu = require( '@stdlib/random-base-randu' );
var Float64Array = require( '@stdlib/array-float64' );
var circularArrayStream = require( '@stdlib/streams-node-from-circular-array' );

function log( v ) {
    console.log( v.toString() );
}

// Create an array containing uniformly distributed pseudorandom numbers:
var arr = new Float64Array( 10 );

var i;
for ( i = 0; i < arr.length; i++ ) {
    arr[ i ] = randu();
}

// Convert the array to a stream:
var opts = {
    'objectMode': true,
    'iter': arr.length * 3
};
var stream = circularArrayStream( arr, opts );

// Create a writable stream for inspecting stream data:
opts = {
    'objectMode': true
};
var iStream = inspectStream( opts, log );

// Begin data flow:
stream.pipe( iStream );

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.