crlfinputstream.java

java 开发的一个电子邮局,挺实用的

/*
 * CRLFInputStream.java
 * Copyright (C) 1999 dog <[e-mail]>
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 * 
 * This library 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
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser 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
 * 
 * You may retrieve the latest version of this library from
 * http://www.dog.net.uk/knife/
 */

package dog.mail.util;

import java.io.*;

/**
 * An input stream that filters out CR/LF pairs into LFs.
 *
 * @author [e-mail]
 * @version 1.0
 */
public class CRLFInputStream extends PushbackInputStream {

	/**
	 * The CR octet.
	 */
	public static final int CR = 13;
	
	/**
	 * The LF octet.
	 */
	public static final int LF = 10;
	
	/**
	 * Constructs a CR/LF input stream connected to the specified input stream.
	 */
	public CRLFInputStream(InputStream in) {
		super(in);
	}

	/**
	 * Constructs a CR/LF input stream connected to the specified input stream, with the specified pushback buffer size.
	 */
	public CRLFInputStream(InputStream in, int bufsize) {
		super(in, bufsize);
	}

	/**
	 * Reads the next byte of data from this input stream.
	 * Returns -1 if the end of the stream has been reached.
	 * @exception IOException if an I/O error occurs
	 */
	public int read() throws IOException {
		int c = super.read();
		if (c==CR) // skip CR
			return super.read();
		return c;
	}

	/**
	 * Reads up to b.length bytes of data from this input stream into
	 * an array of bytes.
	 * Returns -1 if the end of the stream has been reached.
	 * @exception IOException if an I/O error occurs
	 */
	public int read(byte[] b) throws IOException {
		return read(b, 0, b.length);
	}
	
	/**
	 * Reads up to len bytes of data from this input stream into an
	 * array of bytes, starting at the specified offset.
	 * Returns -1 if the end of the stream has been reached.
	 * @exception IOException if an I/O error occurs
	 */
	public int read(byte[] b, int off, int len) throws IOException {
		int l = super.read(b, off, len);
		return removeCRs(b, off, l);
	}

	/**
	 * Reads a line of input terminated by LF.
	 * @exception IOException if an I/O error occurs
	 */
	public String readLine() throws IOException {
		byte[] acc = new byte[4096];
		int count = 0;
		for (byte b=(byte)read(); b!=LF && b!=-1; b=(byte)read())
			acc[count++] = b;
		if (count>0) {
			byte[] bytes = new byte[count];
			System.arraycopy(acc, 0, bytes, 0, count);
			return new String(bytes);
		} else
			return null;
	}

	int removeCRs(byte[] b, int off, int len) {
		for (int index = indexOfCR(b, off, len); index>-1; index = indexOfCR(b, off, len)) {
			for (int i=index; i<b.length-1; i++)
				b[i] = b[i+1];
			len--;
		}
		return len;
	}

	int indexOfCR(byte[] b, int off, int len) {
		for (int i=off; i<off+len; i++)
			if (b[i]==CR) return i;
		return -1;
	}
	
}