2011-01-28 Osaka Node gakuen 1 slide / 大阪Node学園一時限目 発表スライド

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

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

3. Agenda
• Summary
• Usage
• Case study
• Stream classes

4. Stream summary
• An abstract interface Node's I/O
• Controls data stream
• Readable / Writable stream

5. Case study
How to copy files on Node ?

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

7. 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.');
});
});

8. var fs = require('fs');
var readStream = fs.createReadStream('./original.jpg');
var writeStream = fs.createWriteStream('./copy.jpg');
readStream.resume();
readStream.on('data', function (buffer) {
writeStream.write(buffer);
});
readStream.on('end', function () {
writeStream.end();
});
writeStream.on('close', function () {
console.log('copied');
});

9. 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');
});

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

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

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

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

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

15. var fs = require('fs');
var readStream = fs.createReadStream('./original.jpg');
var writeStream = fs.createWriteStream('./copy.jpg');
readStream.resume();
readStream.on('data', function (buffer) {
writeStream.write(buffer);
});
readStream.on('end', function () {
writeStream.end();
});
writeStream.on('close', function () {
console.log('copied');
});

16. Stream usage /
Stream pipe()
pipe
Source stream Destination stream
(readable) (writable)

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

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

19. 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');
});

20. Case study 2
Digest SHA1 hash of a file

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

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

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

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

25. Stream classes
fs.Readable
pipe zlib.Gzip
pipe http.response

26. 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