Learning a node stream

Learning a Node stream 2012-01-28 kumatch / Yosuke Kumakura

• Yosuke Kumakura (kumatch)• @kumatch• Feedtailor inc.• Video game fun

Agenda• Summary• Usage• Case study• Stream classes

Stream summary• An abstract interface Nodes I/O• Controls data stream• Readable / Writable stream

Case studyHow to copy ﬁles on Node ?

var fs = require(fs);var input = ./oriainal.jpg;var output = ./copy.jpg;var data = fs.readFileSync(input);fs.writeFileSync(output, data);console.log(copied.);

var fs = require(fs);var input = ./original.jpg;var output = ./copy.jpg;fs.readFile(input, function (err, data) { if (err) throw err; fs.writeFile(output, data, function (err) { if (err) throw err; console.log(copied.); });});

var fs = require(fs);var readStream = fs.createReadStream(./original.jpg);var writeStream = fs.createWriteStream(./copy.jpg);readStream.pipe(writeStream);writeStream.on(close, function () { console.log(copied);});

Stream usage• Stream is EventEmmiter• and has some methods.

Stream usage / Readable stream• Methods • resume • pause • destroy

Stream usage / Readable stream• Events • data • end • close • error

Stream usage / Writable stream• Methods • write • end • destroy

Stream usage / Writable stream• Events • drain • close • error

Stream usage / Stream pipe() pipeSource stream Destination stream (readable) (writable)

Stream usage / Stream pipe()• destination.write() if source on ‘data’.• source.pause() if destination buffer is full.• source.resume() if destination on ‘drain’.

Stream usage / Stream pipe()• [optional] Keeps the destination stream open. • Do not destination.end().

var fs = require(fs);var readStream = fs.createReadStream(./original.jpg);var writeStream = fs.createWriteStream(./copy.jpg);readStream.pipe(writeStream);writeStream.on(close, function () { console.log(copied);});

Case study 2Digest SHA1 hash of a ﬁle

Stream classes• Filesystem (fs) • readStream (Readable) • writeStream (Writable)

Stream classes• Net • net.Socket (Readable/Writable)

Stream classes• HTTP • http.ServerRequest (Readable) • http.ServerResponse (Writable)

Stream classes• Zlib • all classes (Readable/Writable) • Gzip/Gunzip • Deflate/Inflate • DeflateRaw/InflateRaw

Stream classesfs.Readable pipe zlib.Gzip pipe http.response

References• Node manual & documentation• by Jxck • http://d.hatena.ne.jp/Jxck/20111204• A future in stream / Streams2 (Github issue) • https://github.com/joyent/node/pull/1681

Learning a node stream

by kumatch kumatch on Jan 28, 2012

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Learning a node stream — Presentation Transcript