Constant Stream

Usage

var constantStream = require( '@stdlib/streams/node/from-constant' );

constantStream( value[, options] )

Returns a readable stream which always streams the same value.

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

var iStream;
var stream;

function log( chunk, i ) {
    console.log( chunk.toString() );
    if ( i === 10 ) {
        stream.destroy();
    }
}

stream = constantStream( 'beep' );
iStream = inspectStream( log );

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'.
• iter: number of iterations.

To set stream options,

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

var stream = constantStream( 'beep', opts );

By default, the function returns a stream which streams an infinite number of values (i.e., the stream will never end). 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 = constantStream( 'beep', opts );
var iStream = inspectStream( log );

stream.pipe( iStream );

By default, when not operating in objectMode, a returned stream delineates streamed 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 opts = {
    'iter': 10,
    'sep': ','
};

var stream = constantStream( 'beep', opts );
var iStream = inspectStream( log );

stream.pipe( iStream );

constantStream.factory( [value, ][options] )

Returns a function for creating readable streams which always stream the same provided value.

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

var createStream = constantStream.factory( opts );

If provided a value to stream, the returned function returns readable streams which always stream the same value.

var createStream = constantStream.factory( 'beep' );

var stream1 = createStream();
var stream2 = createStream();
// ...

If not provided a value to stream, the returned function requires that a value be provided at each invocation.

var createStream = constantStream.factory();

var stream1 = createStream( 'beep' );
var stream2 = createStream( 'boop' );
// ...

The method accepts the same options as constantStream().

constantStream.objectMode( value[, 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 value = {
    'beep': 'boop'
};
var opts = {
    'iter': 10
};
var stream = constantStream.objectMode( value, opts );

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

stream.pipe( iStream );

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