05. Stream Stream

1. All Stream objects are also instances of EventEmitter, and the events commonly used by Stream objects are
   

   event name	Triggering conditions
   data	Triggered when there is data to read
   end	Triggered when there is no data to read
   error	Triggered when an error occurs during reading or writing
   finish	Fired when all data has been written to the underlying system

2. Read data from stream read
   data readData.js code is as follows

   var fs = require('fs');
   
   var readerStream = fs.createReadStream('input.txt');
   readerStream.setEncoding('UTF-8');
   
   var data = '';
   
   readerStream.on('data',function(chunk){
       data += chunk;
   });
   
   readerStream.on('end',function(){
   	console.log(data);
   });
   
   readerStream.on('error',function(err){
   	console.log('Custom error log:',err.stack);
   });
   
   console.log('Program completed');

    operation result
   

   >node readData.js
   program is completed
   Here is the tested file;
      hello,this is a test file.
   
   

    
3. Write data to the stream write
   data writeData.js code is as follows
   

   var fs = require('fs');
   
   var writerStream = fs.createWriteStream('output.txt');
   
   writerStream.write('Really, I didn't go out in such a good weather sss','utf-8');
   writerStream.end();
   
   writerStream.on('finish',function(){
     console.log('写入完成');
   });
   
   writerStream.on('error',function(err){
   	console.log('自定义错误日志:',err.stack);
   });
   
   console.log('程序执行完毕');

    运行结果如下
   

   >node Stream.js
   程序执行完毕
   写入完成
   

    
4. 管道与链式流
     pipeStream.js代码如下
   

   var fs = require('fs');
   var zlib = require('zlib');
   
   var readerStream = fs.createReadStream('input.txt');
   var writeCompressGz = fs.createWriteStream('compress.txt.gz');
   
   writeCompressGz.on('finish',function(){
   	fs.createReadStream('compress.txt.gz')
            .pipe(zlib.createGunzip())
            .pipe(fs.createWriteStream('compress.txt'));
   });
   
   readerStream.pipe(zlib.createGzip()).pipe(writeCompressGz);
   
   console.log('程序执行完毕');