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/*
* $Id: LineInputStream.java,v 1.4 2004/07/30 19:06:45 dog Exp $
* Copyright (C) 2002 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.util;
import java.io.ByteArrayOutputStream;
import java.io.FilterInputStream;
import java.io.InputStream;
import java.io.IOException;
/**
* An input stream that can read lines of input.
*
* @author <a href="mailto:dog@gnu.org">Chris Burdess</a>
* @version $Revision: 1.4 $ $Date: 2004/07/30 19:06:45 $
*/
public class LineInputStream extends FilterInputStream
{
/*
* Line buffer.
*/
private ByteArrayOutputStream buf;
/*
* Encoding to use when translating bytes to characters.
*/
private String encoding;
/*
* End-of-stream flag.
*/
private boolean eof;
/**
* Whether we can use block reads.
*/
private final boolean blockReads;
/**
* Constructor using the US-ASCII character encoding.
* @param in the underlying input stream
*/
public LineInputStream (InputStream in)
{
this (in, "US-ASCII");
}
/**
* Constructor.
* @param in the underlying input stream
* @param encoding the character encoding to use
*/
public LineInputStream (InputStream in, String encoding)
{
super (in);
buf = new ByteArrayOutputStream ();
this.encoding = encoding;
eof = false;
blockReads = in.markSupported ();
}
/**
* Read a line of input.
*/
public String readLine ()
throws IOException
{
if (eof)
{
return null;
}
do
{
if (blockReads)
{
// Use mark and reset to read chunks of bytes
final int MIN_LENGTH = 1024;
int len, pos;
len = in.available ();
len = (len < MIN_LENGTH) ? MIN_LENGTH : len;
byte[] b = new byte[len];
in.mark (len);
// Read into buffer b
len = in.read (b, 0, len);
// Handle EOF
if (len == -1)
{
eof = true;
if (buf.size () == 0)
{
return null;
}
else
{
// We don't care about resetting buf
return buf.toString (encoding);
}
}
// Get index of LF in b
pos = indexOf (b, len, (byte) 0x0a);
if (pos != -1)
{
// Write pos bytes to buf
buf.write (b, 0, pos);
// Reset stream, and read pos + 1 bytes
in.reset ();
pos += 1;
while (pos > 0)
{
len = in.read (b, 0, pos);
pos -= len;
}
// Return line
String ret = buf.toString (encoding);
buf.reset ();
return ret;
}
else
{
// Append everything to buf and fall through to re-read.
buf.write (b, 0, len);
}
}
else
{
// We must use character reads in order not to read too much
// from the underlying stream.
int c = in.read ();
switch (c)
{
case -1:
eof = true;
if (buf.size () == 0)
{
return null;
}
case 0x0a: // LF
String ret = buf.toString (encoding);
buf.reset ();
return ret;
default:
buf.write (c);
}
}
}
while (true);
}
private int indexOf (byte[] b, int len, byte c)
{
for (int pos = 0; pos < len; pos++)
{
if (b[pos] == c)
{
return pos;
}
}
return -1;
}
}
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