Java implementation Buffer Multithreading No blocking read remote files

I usually like to listen to music from the Internet, some links download speed is too slow. If you use the HttpURLConnection class method to open the connection, and then use the InputStream class to obtain the input stream, and then use Bufferedinputstream constructs the input stream with the buffer, if the speed is too slow, no matter how large the buffer settings, It all sounds intermittent and does not achieve the purpose of a real buffer. So I tried to write code to read the remote file in a buffered way, and the following code was part of the MP3 decoder I wrote. I do not agree with the use of multi-threaded download, plus some link download speed itself is relatively fast, so in the case of sufficient download speed, let the download thread exit until only one download thread left. Of course, a headache deadlock problem in multiple threads, httpurlconnection timeout blocking issues can make your code look incredibly complex.

This paper briefly introduces the method of realizing multithreading circular buffering. The buffer buf[] is divided into 16 pieces, each 32K, the download thread is responsible for writing data to the buffer, each write a piece; Read thread (Buffrandacceurl Class) reads any byte less than 32K at a time. Synchronous Description: Write/write mutually exclusive wait free block, write/write concurrent fill buf[]; read/write concurrent use buf[].

After I used it for a long time, I think it is more satisfying to achieve my goal, compared with other MP3 players, my method can be relatively smooth and stable download and playback. I put the implementation of multi-threaded download buffering method written out, the shortcomings of the request to criticize.

First, the Httpreader class function: HTTP protocol reads data from the specified URL

/** *//** * Author by http://www.bt285.cn http://www.5a520.cn/package instream;　　 
Import java.io.IOException;　　 
Import Java.io.InputStream;　　 
Import java.net.HttpURLConnection;　　 
　 
Import Java.net.URL;　　 
　　　 Public final class Httpreader {public static final int max_retry = 10;　　 
　　　 private static long content_length;　　 
　　　 Private URL URL;　　 
　　　 Private HttpURLConnection httpconnection;　　 
　　　 Private InputStream In_stream;　　　　　　　　　　 Private long Cur_pos;　　 
　　　 Used to determine whether the Seek method performs a file positioning private int connect_timeout;　　 
　　　　　　 
　　　 private int read_timeout;　　 
　　　 Public Httpreader (URL u) {This (U, 5000, 5000); Public Httpreader (URL u, int connect_timeout, int read_timeout) {this.connect_timeout = con　　 
　　　　　　　 Nect_timeout;　　 
　　　　　　　 This.read_timeout = Read_timeout;　　 
　　　　　　　 url = u;　　 
　　　　　　　　　　　 if (content_length = = 0) {int retry = 0;　　 
　　　　　　　　　　while (Retry < httpreader.max_retry)　　　　　 try {this.seek (0);　　 
　　　　　　　　　　　　　　　　　　　 Content_length = Httpconnection.getcontentlength ();　　 
　　　　　　　　　　　　　　　 Break　　 
　　　　　　　　　　　　　　　 catch (Exception e) {retry++;　　 
　　　 }} public static long Getcontentlength () {return content_length; public int read (byte[] b, int off, int len) throws IOException {int r = in_stream.read (b, O　　 
　　　　　　　 FF, Len);　　 
　　　　　　　 Cur_pos + = r;　　 
　　　 return R;　　 
　　　　　　　 public int getData (byte[] b, int off, int len) throws IOException {int r, Rema = Len; while (Rema > 0) {if ((R = in_stream.read (b, off, rema)) = = 1) {return-1　　 
　　　　　　　　　　　 ;　　 
　　　　　　　　　　　 } Rema = R;　　 
　　　　　　　　　　　 Off + = r;　　 
　　　　　　　 Cur_pos + = r;　　 
　　　 return Len; public void Close () {if (HTTPCO)Nnection!= null) {httpconnection.disconnect ();　　 
　　　　　　　 Httpconnection = null;　　 
　　　　　　　　　　　 } if (In_stream!= null) {try {in_stream.close ();　　 
　　　　　　　 The catch (IOException e) {} in_stream = null;　　 
　　　 } URL = null; /**//* * Throw exception Notification Retry * Response Code 503 may be caused by some temporary reason, for example, the same IP frequent connection request may be rejected by the server/public voi

　　 
　　　　　　　　　　　 D Seek (Long Start_pos) throws IOException {if (Start_pos = = Cur_pos && in_stream!= null)　　 
　　　　　　　 Return　　 
　　　　　　　　　　　 if (httpconnection!= null) {httpconnection.disconnect ();　　 
　　　　　　　 Httpconnection = null;　　 
　　　　　　　　　　　 } if (In_stream!= null) {in_stream.close ();　　 
　　　　　　　 In_stream = null;　　 
　　　　　　　 } httpconnection = (httpurlconnection) url.openconnection ();　　 
　　　　　　　 Httpconnection.setconnecttimeout (connect_timeout); Httpconnection.setReadTimeout (read_timeout);　　 
　　　　　　　 String sproperty = "bytes=" + Start_pos + "-";

　　 
　　　　　　　 Httpconnection.setrequestproperty ("Range", Sproperty);　　 
　　　　　　　 Httpconnection.setrequestproperty ("Connection", "keep-alive");　

　 
　　　　　　　 int responsecode = Httpconnection.getresponsecode ();　　 
　　　　　　　　　　　 if (Responsecode < | | Responsecode >=) {try {thread.sleep (500);　　 
　　　　　　　　　　　 catch (Interruptedexception e) {e.printstacktrace ();　　 
　　　　　　　 } throw new IOException ("HTTP responsecode=" +responsecode);　　 
　　　　　　　 } In_stream = Httpconnection.getinputstream ();　　 
　　　 Cur_pos = Start_pos; }　　 　 }