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brake

Throttle a stream with backpressure.

build status

example

Take a bulk readable stream stream and throttle it down to 10 bytes per second:

var Stream = require('stream');
var brake = require('brake');

var bulk = (function () {
    var s = new Stream;
    s.readable = true
    s.pause = function () {
        clearInterval(iv);
    };
    s.resume = function () {
        iv = createInterval();
    };
    
    var iv = createInterval();
    var x = 0;
    function createInterval () {
        return setInterval(function () {
            s.emit('data', String(x));
            x = x ^ 1;
        }, 5);
    }
    return s;
})();

bulk
    .pipe(brake(10))
    .pipe(process.stdout, { end : false })
;

There's also a brake command as part of this package:

$ brake 30 README.markdown
brake
=====

Throttle a stream with backpressure.

[![build status](http^C

methods

var brake = require('brake')

var b = brake(rate, opts)

var b = brake(rate, period)

var b = brake(opts)

Return a readable/writable, pause-able/resumable stream that applies backpressure when more data than the rate allows are written.

options:

  • rate - how many bytes to emit for each interval of length period

  • period - How often to check the output length in milliseconds. Default value: 1000.

  • smooth - If set, set the rate to 1 and divide the period by the rate. Defaults to true when opts.period is not specified.

  • maxSize - if set, throw an error if the total size of the pending writes exceed this value

When more bytes than the rate allows are written, .write() returns false and will start buffering data.

b.pause()

Explicitly turn on buffering. Writes will return false until .resume() is called.

b.resume()

Un-pause a stream, triggering the interval to see if data can be emitted.

command-line usage

usage:
    
    brake OPTIONS [rate] {file | -}
    brake OPTIONS [rate] [period] {file | -}
    brake OPTIONS {file | -}

OPTIONS:

  -r, --rate     How many bytes to emit for each interval of length `period`
  
  -p, --period   How often to check the output length in milliseconds.
                 default value: 1000

  -s, --smooth   If set, set the rate to 1 and divide the period by the rate.
                 Defaults to `true` when period is not specified.

  -m, --maxsize  If set, throw an error if the total size of the pending writes
                 exceed this value

install

To get the library, with npm do:

npm install brake

To get the command, with npm do:

npm install -g brake

license

MIT