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Node.js File system & Streams

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Node.js File system & Streams

Node.js File system & Streams

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  • 1. © 2014 All rights reserved. Tel: 054-5-767-300, Email: evardi@gmail.com
  • 2. © 2014 All rights reserved. Tel: 054-5-767-300, Email: evardi@gmail.com
  • 3. © 2014 All rights reserved. Tel: 054-5-767-300, Email: evardi@gmail.com
  • 4. © 2014 All rights reserved. Tel: 054-5-767-300, Email: evardi@gmail.com var path = require("path");
  • 5. © 2014 All rights reserved. Tel: 054-5-767-300, Email: evardi@gmail.com var fs = require("fs");
  • 6. © 2014 All rights reserved. Tel: 054-5-767-300, Email: evardi@gmail.com
  • 7. © 2014 All rights reserved. Tel: 054-5-767-300, Email: evardi@gmail.com var Stream = require("stream"); var stream = new Stream(); var duration = 5 * 1000; // 5 seconds var end = Date.now() + duration; var interval; stream.readable = true; interval = setInterval(function () { console.log("Emitting a data event"); stream.emit("data", new Buffer("foo")); if (Date.now() >= end) { console.log("Emitting an end event"); stream.emit("end"); clearInterval(interval); } }, 1000);
  • 8. © 2014 All rights reserved. Tel: 054-5-767-300, Email: evardi@gmail.com
  • 9. © 2014 All rights reserved. Tel: 054-5-767-300, Email: evardi@gmail.com  crypto streams  tcp sockets  child process stdout and stderr  process.stdin
  • 10. © 2014 All rights reserved. Tel: 054-5-767-300, Email: evardi@gmail.com
  • 11. © 2014 All rights reserved. Tel: 054-5-767-300, Email: evardi@gmail.com var fs = require("fs"); var stream; stream = fs.createReadStream(__dirname + "/foo.txt"); stream.on("data", function (data) { var chunk = data.toString(); process.stdout.write(chunk); }); stream.on("end", function() { console.log(); });
  • 12. © 2014 All rights reserved. Tel: 054-5-767-300, Email: evardi@gmail.com var fs = require("fs"); var readStream = fs.createReadStream(__dirname + "/foo.txt"); var writeStream = fs.createWriteStream(__dirname + "/bar.txt"); readStream.pipe(writeStream);
  • 13. var fs = require("fs"); var zlib = require("zlib"); var gzip = zlib.createGzip(); var input = fs.createReadStream("input.txt"); var output = fs.createWriteStream("input.txt.gz"); input .pipe(gzip) .pipe(output);
  • 14. © 2014 All rights reserved. Tel: 054-5-767-300, Email: evardi@gmail.com Use-case Class Method(s) to implement Reading only Readable _read Writing only Writable _write Reading and writing Duplex _read, _write Operate on written data, then read the result Transform _transform, _flush
  • 15. © 2014 All rights reserved. Tel: 054-5-767-300, Email: evardi@gmail.com var Readable = require('stream').Readable; var util = require('util'); util.inherits(Counter, Readable); function Counter(opt) { Readable.call(this, opt); this._max = 1000000; this._index = 1; } Counter.prototype._read = function () { var i = this._index++; if (i > this._max) this.push(null); else { var str = '' + i; var buf = new Buffer(str, 'ascii'); this.push(buf); } };