time-to-botec/js/node_modules/@stdlib/streams/node/from-constant

Constant Stream

Create a readable stream which always streams the same value.

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.

---

Notes

• In binary mode, a provided value must be a string, Buffer, or Uint8Array.
• In objectMode, null is a reserved value. If provided null, the returned stream will prematurely end.
• If provided an object reference, the value is not copied. To avoid unwanted mutation, copy the value before creating a stream.
• In older Node.js environments, Uint8Array contents may be copied to a new Buffer object due to changes in the underlying Node.js APIs.
• If the factory method is provided only one argument and that argument is an object (either empty or not containing any recognized options properties), the method treats the argument as a value to be streamed, not as an options argument.

---

Examples

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

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

var opts = {
    'objectMode': true,
    'iter': 10
};

var stream = constantStream( 3.14, opts );

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

stream.pipe( iStream );

---

CLI

Usage

Usage: constant-stream [options] <value>

Options:

  -h,  --help               Print this message.
  -V,  --version            Print the package version.
       --sep sep            Separator used to join streamed data. Default: '\n'.
  -n,  --iter iterations    Number of iterations.

Notes

• In accordance with POSIX convention, a trailing newline is always appended to generated output prior to exit.

Examples

$ constant-stream 'beep' -n 10