ssh2compressorzlib.java

一个非常好的ssh客户端实现

/******************************************************************************
 *
 * Copyright (c) 1999-2003 AppGate Network Security AB. All Rights Reserved.
 * 
 * This file contains Original Code and/or Modifications of Original Code as
 * defined in and that are subject to the MindTerm Public Source License,
 * Version 2.0, (the 'License'). You may not use this file except in compliance
 * with the License.
 * 
 * You should have received a copy of the MindTerm Public Source License
 * along with this software; see the file LICENSE.  If not, write to
 * AppGate Network Security AB, Otterhallegatan 2, SE-41118 Goteborg, SWEDEN
 *
 *****************************************************************************/

package com.mindbright.ssh2;

import com.jcraft.jzlib.ZStream;
import com.jcraft.jzlib.JZlib;

/**
 * Implements the zlib compression algorithm as described in the ssh protocol
 * draft. It uses the jzlib provided by JCraft to handle the actual
 * compression/uncompression.
 */
public class SSH2CompressorZLib extends SSH2Compressor {

    private final static int DEFLATE_BUF_SIZE = 49152;
    private final static int INFLATE_BUF_SIZE = 65536;

    private ZStream dStream;
    private ZStream iStream;
    private byte[]  dBuf;
    private byte[]  iBuf;

    public SSH2CompressorZLib() {
    }

    public void init(int mode, int level) {
	switch(mode) {
	case COMPRESS_MODE:
	    dStream = new ZStream();
	    dStream.deflateInit(level);
	    dStream.next_out = dBuf = new byte[DEFLATE_BUF_SIZE];
	    break;
	case UNCOMPRESS_MODE:
	    iStream = new ZStream();
	    iStream.inflateInit();
	    iStream.next_out = iBuf = new byte[INFLATE_BUF_SIZE];
	    break;
	default:
	    throw new Error("Unknown mode sent to SSH2CompressorZLib");
	}
    }

    public void compress(SSH2DataBuffer data) throws SSH2CompressionException {
	dStream.next_in        = data.getData();
	dStream.next_in_index  = 9;
	dStream.avail_in       = data.getWPos() - 9;
	dStream.next_out_index = 0;
	dStream.avail_out      = DEFLATE_BUF_SIZE;

	int status = dStream.deflate(JZlib.Z_PARTIAL_FLUSH);

	if(status != JZlib.Z_OK) {
	    throw new SSH2CompressionException("Error in zlib deflate: " +
					       status);
	}

	int dLen = DEFLATE_BUF_SIZE - dStream.avail_out;

	if((dStream.next_in.length - 256) < dLen) {
	    data.setData(new byte[dLen + (dStream.next_in.length >>> 1)]);
	}

	System.arraycopy(dBuf, 0, data.getData(), 9, dLen);
	data.setWPos(9 + dLen);
    }

    public int uncompress(SSH2DataBuffer data, int len)
	throws SSH2CompressionException
    {
	iStream.next_in        = data.getData();
	iStream.next_in_index  = 9;
	iStream.avail_in       = len;
	iStream.next_out_index = 0;
	iStream.avail_out      = INFLATE_BUF_SIZE;

	int status = iStream.inflate(JZlib.Z_PARTIAL_FLUSH);

	if(status != JZlib.Z_OK) {
	    throw new SSH2CompressionException("Error in zlib inflate: " +
					       status);
	}

	int iLen = INFLATE_BUF_SIZE - iStream.avail_out;

	if((iStream.next_in.length - 256) < iLen) {
	    data.setData(new byte[iLen + (iStream.next_in.length >>> 1)]);
	}

	System.arraycopy(iBuf, 0, data.getData(), 9, iLen);

	return iLen;
    }

    public long numOfCompressedBytes() {
	if(iStream != null) {
	    return iStream.total_in;
	}
	return dStream.total_out;
    }

    public long numOfUncompressedBytes() {
	if(iStream != null) {
	    return iStream.total_out;
	}
	return dStream.total_in;
    }

}