THINKING IN SEQUENCES

Streams in Node.js & IO.js

Artur Skowroński

NODE STREAMS 101

Streams Flow

Tran

sfo

rmat

ion

1

Tran

sfo

rmat

ion

2

data

EVENTS:

end

STREAMS1Aka. Push Streams

Readable

Writable

Kinds of Streams

Readable Streams

Examples

fs.createReadStream('file1.txt')

gulp.src('client/templates/*.jade')

Writable Streams

Examples

fs.createWriteStream('file2.txt')

gulp.dest('client/templates/*.jade')

request.on('data', function(data){

response.write(transform(data))

});

Easiest thing that can possibly work… can it?

Readable Stream

Writable Stream

request.on('end', function(){

response.end()

});

Chaining

request.pipe(transform).pipe(response)

request.pipe(response)

Backpressure?

Readable.resume() & Readable.pause()

request.on('data', function(data) {

if (response.write(data) == false){

}

});

response.on('drain', function(data) {

request.resume();

});

request.pause();

STREAMS2Aka. Pull Streams

v 0.10

Kinds of Streams

Readable

Writable

Transform

Duplex

Passthrough

Streams1 Streams2

Readable Streams…strikes back

Example 1

var RStream =

require('stream').Readable;

var rs = new RStream;

rs.push('First Element');

rs.push('Second Element');

rs.push('Third Element');

rs.push(null);

rs.pipe(process.stdout);

var Readable = require('stream').Readable

Subclass stream.Readable

util.inherits(RStream, Readable);

var RStream = function (options){

Readable.call(this, options)

}

Overwritting _read(size) function

RStream.prototype._read = function() {

if (curIndex === data.length)

return this.push(null);

var item = data[curIndex++];

this.push(item);

}

var data = ["First”, "Second”, "Third”];

var curIndex = 0;

Example 2 – Flowing Mode

var readFunct = function(el){

log('received:' + el);

}

str.on('data', readFunct);

str.on('end', function() {

log('All consumed');

});

Example 3 – Non-Flowing Mode

var readFunct = function(){

while (null !== (el = str.read()))

{

log('received:' + str.read()

}

}

str.on('readable', readFunct);

str.on('end', function() {

log('All consumed');

});

Writable StreamsStreams2 Edition

var Writable = require('stream').Writable

Subclass stream.Writable

util.inherits(WStream, Writable);

var WStream = function (options){

Writable.call(this, options)

}

Example 1

var WSImpl = function(chunk, encoding, callback) {

};

WriteStream.prototype._write = WSImpl

console.log('write: ' + JSON.stringify(chunk));

callback();

Example 2

var WSImpl = function(chunk, encoding, callback) {

http.request(“foo.bar?p=" + chunk, function(resp){

resp.on(‘end’, callback);

})

};

Transform Streams…I got a power

var Transform =

require('stream').Transformable

Subclass stream.Transformable

Var TStream = function (options){

Transform.call(this, options)

}

…

How

var TSImpl = function(chunk, encoding, callback) {

console.log('transform : ' + chunk.toUpperCase());

this.push(chunk.toUpperCase());

callback();

};

TransformStream.prototype._transform = TSImpl

Example

readableStream

.pipe(tranformStream)

.pipe(writableStream)

Duplex StreamsGod With Two Faces

Passthrough Streams…because I can

https://github.com/sindresorhus/awesome-nodejs#streams

Awesome NodeJS - Streams

through2

concat-stream

readable-stream

STREAMS3Aka. Combined Streams

v 0.11.5

v 1.0

Pull Push – Streams2 – data event first

stream.on('data

});

stream.on('readable',

Pull Push – Streams2 -Pull Push – Streams2 – readable event first

stream.on('readable', function() {

while(var chunk = stream.read()) {

pullD += chunk;

}

});

stream.on('data', function(chunk) {

pushD += chunk;

});

Pull Push – Streams3

HIGHLAND

https://github.com/caolan/highland

npm install highland

Links

http://nodestreams.com/

Node.js Streams Playground

http://nodeschool.io/

Node.js School – Stream Adventure

https://github.com/substack/stream-handbook

Streams Handbook

Artur Skowroński

Thank You!

… and waiting for questions!@ArturSkowronski

arturskowronski.com

github.com/ArturSkowronski

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