crlfoutputstream.java

java高级使用教程 全书一共分六章

// CrLfOutputStream - RFC977-style output stream
//
// Copyright (C) 1996 by Jef Poskanzer <[e-mail]>.  All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 1. Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
// OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
// OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
// SUCH DAMAGE.
//
// Visit the ACME Labs Java page for up-to-date versions of this and other
// fine Java utilities: http://www.acme.com/java/

package Acme.Nnrpd;

import java.io.*;

/// RFC977-style output stream.
// <P>
// NNTP requires that all lines be terminated by CR LF.  This stream
// takes standard Java LF-terminated lines and inserts the CRs.
// <P>
// <A HREF="/resources/classes/Acme/Nnrpd/CrLfOutputStream.java">Fetch the software.</A><BR>
// <A HREF="/resources/classes/Acme.tar.gz">Fetch the entire Acme package.</A>

public class CrLfOutputStream extends FilterOutputStream
    {

    static final byte cr = 13;
    static final byte lf = 10;
    static final byte[] crlf = { cr, lf };

    /// Constructor.
    public CrLfOutputStream( OutputStream out )
	{
	super( out );
	}

    /// Writes a byte.  This method will block until the byte is actually
    // written.
    // @param b the byte to be written
    // @exception IOException if an I/O error has occurred
    public void write( int b ) throws IOException
	{
	if ( b == lf )
	    out.write( crlf, 0, crlf.length );
	else
	    out.write( b );
	}

    /// Writes a subarray of bytes.
    // @param b	the data to be written
    // @param off the start offset in the data
    // @param len the number of bytes that are written
    // @exception IOException if an I/O error has occurred
    public void write( byte b[], int off, int len ) throws IOException
	{
	int endOff = off + len;
	int writtenOff = off;
	for ( int i = off; i < len; ++i )
	    {
	    if ( b[i] == lf )
		{
		if ( writtenOff < i )
		    out.write( b, writtenOff, i - writtenOff );
		out.write( crlf, 0, crlf.length );
		writtenOff = i + 1;
		}
	    }
	if ( writtenOff < endOff )
	    out.write( b, writtenOff, endOff - writtenOff );
	}

    }