pushbackstream.java

java实现的多媒体播放器,可以在手机上运行

/**
 *-----------------------------------------------------------------------
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Library General Public License as published
 *   by the Free Software Foundation; either version 2 of the License,or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU Library General Public License for more details.
 *
 *   You should have received a copy of the GNU Library General Public
 *   License along with this program; if not,write to the Free Software
 *   Foundation,Inc.,675 Mass Ave,Cambridge,MA 02139,USA.
 *----------------------------------------------------------------------
 */
package javazoom.jlme.decoder;


import java.io.InputStream;
import java.io.IOException;

public class PushBackStream{
    private byte[] buf;
    private int pos,temp,temp2,avail;
    private long pskip;
    private InputStream in;

    public PushBackStream(InputStream in,int size) {
	this.in = in;
        this.buf = new byte[size];
	this.pos = size;
    }

    public int read(byte[] b,int off,int len) throws IOException {
        avail = buf.length - pos;
	if (avail > 0) {
	    if (len < avail)
		avail = len;

            if(avail==3){
              temp = pos;
              temp2 = off;
              b[temp2++] = buf[temp++];
              b[temp2++] = buf[temp++];
              b[temp2] = buf[temp];
            }
            else{ //equals 1
              b[off]= buf[pos];
            }

            pos += avail;
	    off += avail;
	    len -= avail;
	}

        if (len > 0) {
          if ((len = in.read(b,off,len)) == -1)
            return avail == 0 ? -1 : avail;

          return avail + len;
	}

        return avail;
    }


    public void unread(byte[] b,int off,int len){
	temp = pos -= 4;

        buf[temp++] = b[off++];
        buf[temp++] = b[off++];
        buf[temp++] = b[off++];
        buf[temp] = b[off++];
    }

    public synchronized void close() throws IOException {
        if (in == null)
            return;
        in.close();
        in = null;
        buf = null;
    }

}