Usage

1var randomStream = require( '@stdlib/random-streams-minstd-shuffle' );

randomStream( [options] )

Returns a readable stream for a linear congruential pseudorandom number generator (LCG) whose output is shuffled.

1var inspectStream = require( '@stdlib/streams-node-inspect-sink' );
2
3var iStream;
4var stream;
5
6function log( chunk, idx ) {
7    console.log( chunk.toString() );
8    if ( idx === 10 ) {
9        stream.destroy();
10    }
11}
12
13stream = randomStream();
14iStream = inspectStream( log );
15
16stream.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 ceasing to generate additional pseudorandom numbers.
• 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.
• normalized: boolean indicating whether to return pseudorandom numbers on the interval [0,1).
• seed: pseudorandom number generator seed.
• state: an Int32Array containing pseudorandom number generator state. If provided, the function ignores the seed option.
• copy: boolean indicating whether to copy a provided pseudorandom number generator state. Setting this option to false allows sharing state between two or more pseudorandom number generators and/or streams. Setting this option to true ensures that a stream generator has exclusive control over its internal state. Default: true.
• siter: number of iterations after which to emit the pseudorandom number generator state. This option is useful when wanting to deterministically capture a stream's underlying PRNG state. Default: 1e308.

To set stream options,

1var opts = {
2    'objectMode': true,
3    'encoding': 'utf8',
4    'highWaterMark': 64
5};
6
7var stream = randomStream( opts );

By default, the function returns a stream which can generate an infinite number of values (i.e., the stream will never end). To limit the number of generated pseudorandom numbers, set the iter option.

1var inspectStream = require( '@stdlib/streams-node-inspect-sink' );
2
3function log( chunk ) {
4    console.log( chunk.toString() );
5}
6
7var opts = {
8    'iter': 10
9};
10
11var stream = randomStream( opts );
12var iStream = inspectStream( log );
13
14stream.pipe( iStream );

To return pseudorandom numbers on the interval [0,1), set the normalized option.

1var inspectStream = require( '@stdlib/streams-node-inspect-sink' );
2
3function log( chunk ) {
4    console.log( chunk.toString() );
5}
6
7var opts = {
8    'iter': 10,
9    'normalized': true
10};
11
12var stream = randomStream( opts );
13var iStream = inspectStream( log );
14
15stream.pipe( iStream );

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

1var inspectStream = require( '@stdlib/streams-node-inspect-sink' );
2
3function log( chunk ) {
4    console.log( chunk.toString() );
5}
6
7var opts = {
8    'iter': 10,
9    'sep': ','
10};
11
12var stream = randomStream( opts );
13var iStream = inspectStream( log );
14
15stream.pipe( iStream );

To seed the underlying pseudorandom number generator, set the seed option.

1var inspectStream = require( '@stdlib/streams-node-inspect-sink' );
2
3function log( v ) {
4    console.log( v );
5}
6
7var opts = {
8    'objectMode': true,
9    'iter': 10,
10    'seed': 1234
11};
12
13var stream = randomStream( opts );
14
15opts = {
16    'objectMode': true
17};
18var iStream = inspectStream( opts, log );
19
20stream.pipe( iStream );

To return a readable stream with an underlying pseudorandom number generator having a specific initial state, set the state option.

1var inspectStream = require( '@stdlib/streams-node-inspect-sink' );
2
3function log( v ) {
4    console.log( v );
5}
6
7var opts1 = {
8    'objectMode': true,
9    'iter': 10
10};
11
12var stream = randomStream( opts1 );
13
14var opts2 = {
15    'objectMode': true
16};
17var iStream = inspectStream( opts2, log );
18
19// Stream pseudorandom numbers, thus progressing the underlying generator state:
20stream.pipe( iStream );
21
22// Create a new PRNG stream initialized to the last state of the previous stream:
23var opts3 = {
24    'objectMode': true,
25    'iter': 10,
26    'state': stream.state
27};
28
29stream = randomStream( opts3 );
30iStream = inspectStream( opts2, log );
31
32// Stream pseudorandom numbers starting from the last state of the previous stream:
33stream.pipe( iStream );

stream.seed

The value used to seed the underlying pseudorandom number generator.

1var stream = randomStream();
2
3var seed = stream.seed;
4// returns <Int32Array>

stream.seedLength

Length of underlying pseudorandom number generator seed.

1var stream = randomStream();
2
3var len = stream.seedLength;
4// returns <number>

stream.state

Writable property for getting and setting the underlying pseudorandom number generator state.

1var stream = randomStream();
2
3var state = stream.state;
4// returns <Int32Array>

stream.stateLength

Length of underlying pseudorandom number generator state.

1var stream = randomStream();
2
3var len = stream.stateLength;
4// returns <number>

stream.byteLength

Size (in bytes) of underlying pseudorandom number generator state.

1var stream = randomStream();
2
3var sz = stream.byteLength;
4// returns <number>

randomStream.factory( [options] )

Returns a function for creating readable streams which generate pseudorandom numbers via a linear congruential pseudorandom number generator (LCG) whose output is shuffled.

1var opts = {
2    'objectMode': true,
3    'encoding': 'utf8',
4    'highWaterMark': 64
5};
6
7var createStream = randomStream.factory( opts );

The method accepts the same options as randomStream().

randomStream.objectMode( [options] )

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

1var inspectStream = require( '@stdlib/streams-node-inspect-sink' );
2
3function log( v ) {
4    console.log( v );
5}
6
7var opts = {
8    'iter': 10
9};
10var stream = randomStream.objectMode( opts );
11
12opts = {
13    'objectMode': true
14};
15var iStream = inspectStream( opts, log );
16
17stream.pipe( iStream );

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

Events

In addition to the standard readable stream events, the following events are supported...

'state'

Emitted after internally generating siter pseudorandom numbers.

1var opts = {
2    'siter': 10 // emit the PRNG state every 10 pseudorandom numbers
3};
4
5var stream = randomStream( opts );
6
7stream.on( 'state', onState );
8
9function onState( state ) {
10    // Do something with the emitted state, such as save to file...
11}