compressedinputstream.java

来自「kaffe Java 解释器语言,源码,Java的子集系统,开放源代码」· Java 代码 · 共 179 行

/*
 * $Id: CompressedInputStream.java,v 1.1 2004/01/10 23:34:31 dalibor Exp $
 * Copyright (C) 2003 The Free Software Foundation
 * 
 * This file is part of GNU inetlib, a library.
 * 
 * GNU inetlib is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * GNU inetlib 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 General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 * 
 * As a special exception, if you link this library with other files to
 * produce an executable, this library does not by itself cause the
 * resulting executable to be covered by the GNU General Public License.
 * This exception does not however invalidate any other reasons why the
 * executable file might be covered by the GNU General Public License.
 */

package gnu.inet.ftp;

import java.io.InputStream;
import java.io.IOException;
import java.net.ProtocolException;

/**
 * A DTP input stream that implements the FTP compressed transfer mode.
 *
 * @author <a href='mailto:[e-mail]'>Chris Burdess</a>
 * @version $Revision: 1.1 $ $Date: 2004/01/10 23:34:31 $
 */
class CompressedInputStream extends DTPInputStream
{

    static final int EOF = 64;
    
    static final int RAW = 0x00;
    static final int COMPRESSED = 0x80;
    static final int FILLER = 0xc0;
    
    int descriptor;
    int max = -1;
    int count = -1;
    
    int state = RAW;              // RAW | STATE | FILLER
    int rep;                      // the compressed byte
    int n = 0;                    // the number of compressed or raw bytes
    
    CompressedInputStream(DTP dtp, InputStream in)
    {
        super(dtp, in);
    }
    
    public int read() throws IOException
    {
        if (transferComplete)
            return -1;
        if (count == -1)
            readHeader();
        if (max < 1)
        {
            close();
            return -1;
        }
        if (n > 0 && (state == COMPRESSED || state == FILLER))
        {
            n--;
            return rep;
        }
        int c = in.read();
        if (c == -1)
            close();
        count++;
        if (count >= max)
        {
            count = -1;
            if (descriptor == EOF)
                close();
        }
        if (c == -1)
            return c;
        while (n == 0)              // read code header
        {
            state = (c & 0xc0);
            n = (c & 0x3f);
            c = in.read();
            if (c == -1)
                return -1;
        }
        switch (state)
        {
          case RAW:
            break;
          case COMPRESSED:
          case FILLER:
            rep = c;
            break;
          default:
            throw new ProtocolException("Illegal state: " + state);
        }
        n--;
        return c;
    }
    
    public int read(byte[] buf) throws IOException
    {
        return read(buf, 0, buf.length);
    }
    
    public int read(byte[] buf, int off, int len) throws IOException
    {
        if (transferComplete)
            return -1;
        if (count == -1)
            readHeader();
        if (max < 1)
        {
            close();
            return -1;
        }
        // TODO improve performance
        for (int i = off; i < len; i++)
        {
            int c = read();
            if (c == -1)
            {
                close();
                return i;
            }
            buf[i] = (byte) c;
        }
        return len;
        /*
           int l = in.read(buf, off, len);
           if (l==-1)
           close();
           count += l;
           if (count>=max)
           {
           count = -1;
           if (descriptor==EOF)
           close();
           }
           return l;
           */
    }
    
    /**
     * Reads the block header.
     */
    void readHeader() throws IOException
    {
        descriptor = in.read();
        int max_hi = in.read();
        int max_lo = in.read();
        max = (max_hi << 8) | max_lo;
        count = 0;
    }
    
    /**
     * Reads the code header.
     */
    void readCodeHeader() throws IOException
    {
        int code = in.read();
        state = (code & 0xc0);
        n = (code & 0x3f);
    }
    
}