Node.js（六）【Buffer】【Stream】

Net Buffer Stream

 1  new Buffer(‘Hello 皮卡丘‘)
 2 //<Buffer 48 65 6c 6c 6f 20 e7 9a ae e5 8d a1 e4 b8 98>
 3
 4 new Buffer(‘Hello 皮卡丘‘, ‘base64‘)
 5 //<Buffer 1d e9 65 a1 af>
 6
 7 var buf = new Buffer(‘123456‘);console.log(buf)
 8 //undefined
 9
10 var buf = new Buffer(7);buf.write(‘12345678‘);console.log(buf.length)
11 //7， 超出部分会被忽略掉
12
13  var buf = new Buffer([1,2,3,4]);console.log(buf)
14 //<Buffer 01 02 03 04>

Buffer 用于处理二进制数据
一开始长度被指定了，无论怎么打，长度都不会变

 1 var fs = require(‘fs‘);
 2
 3 fs.readFile(‘imooc_class.jpg‘, function (err, origin_buffer) {
 4     console.log(Buffer.isBuffer(origin_buffer));
 5
 6     fs.writeFile(‘imooc_buffer.jpg‘, origin_buffer, function (err) {
 7         if(err) console.log(err);
 8     });
 9
10     var base64Image = origin_buffer.toString(‘base64‘);
11     console.log(base64Image);
12
13     var decodedImage = new Buffer(base64Image, ‘base64‘);
14     console.log(Buffer.compare(origin_buffer, decodedImage));
15
16     fs.writeFile(‘logo_decoded.jpg‘, decodedImage, function (err) {
17         if(err) console.log(err);
18     });
19 });

Stream流
/**********************************/

 1 var http = require(‘http‘);
 2 var fs = require(‘fs‘);
 3 var request = require(‘request‘);
 4
 5 http.createServer(function (req, res) {
 6     /*fs.readFile(‘imooc_class.jpg‘, function (err, res) {
 7         if(err) {
 8             res.end(‘file not exist!‘);
 9         }else {
10             res.writeHeader(200, {‘Content-Type‘: ‘text/html‘});,
11             res.end(data);
12         }
13     });*/
14
15     //fs.createReadStream(‘imooc_class.jpg‘).pipe(res);
16
17     //爬取网页图片，输出到指定端口
18     request(‘http://imgsrc.baidu.com/forum/w
19
20 %3D580/sign=e2f3b45fa086c91708035231f93c70c6/fb781bd5ad6eddc426e3e45c3edbb6fd53663399.jpg‘).pipe(res);
21 }).listen(8090);

/********************************************/

1 var fs = require(‘fs‘);
2
3 fs.createReadStream(‘1.mp3‘).pipe(fs.createWriteStream(‘1-pipe.mp3‘));

/********************************************/

 1 var stream = require(‘stream‘);
 2
 3 var Readable = stream.Readable;
 4 var Writable = stream.Writable;
 5
 6 //实例化
 7 var readStream = new Readable();
 8 var writStream = new Writable();
 9
10 //可读流
11 readStream.push(‘I ‘);
12 readStream.push(‘Love ‘);
13 readStream.push(‘Node\n‘);
14 //可读流结束
15 readStream.push(null);
16
17 //可写流
18 writStream._write = function (chunk, encode, cb) {
19     console.log(chunk.toString());
20     cb();
21 };
22
23 readStream.pipe(writStream);

/***************************************/

 1 //定制流
 2 var stream = require(‘stream‘);
 3 //工具类
 4 var util = require(‘util‘);
 5
 6 function ReadStream() {
 7     stream.Readable.call(this);
 8 }
 9
10 util.inherits(ReadStream, stream.Readable);
11
12 ReadStream.prototype._read = function () {
13     //可读流
14     this.push(‘I ‘);
15     this.push(‘Love ‘);
16     this.push(‘Node\n‘);
17     //可读流结束
18     this.push(null);
19 };
20
21 function WritStream() {
22     stream.Writable.call(this);
23     this._cached = new Buffer(‘‘);
24 }
25
26 util.inherits(WritStream, stream.Writable);
27
28 WritStream.prototype._write = function (chunk, encode, cb) {
29     console.log(chunk.toString());
30     cb();
31 };
32
33 //转换流
34 function TransformStream() {
35     stream.Transform.call(this);
36 }
37
38 util.inherits(TransformStream, stream.Transform);
39
40 TransformStream.prototype._transform = function (chunk, encode, cb) {
41     this.push(chunk);
42     cb();
43 };
44
45 TransformStream.prototype._flush = function (cb) {
46     this.push(‘Oh Yeah‘);
47 };
48
49 var rs = new ReadStream();
50 var ws = new WritStream();
51 var ts = new TransformStream();
52
53 rs.pipe(ts).pipe(ws);