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/*
* LineInputStream.java
* 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
*
* Linking this library statically or dynamically with other modules is
* making a combined work based on this library. Thus, the terms and
* conditions of the GNU General Public License cover the whole
* combination.
*
* As a special exception, the copyright holders of this library give you
* permission to link this library with independent modules to produce an
* executable, regardless of the license terms of these independent
* modules, and to copy and distribute the resulting executable under
* terms of your choice, provided that you also meet, for each linked
* independent module, the terms and conditions of the license of that
* module. An independent module is a module which is not derived from
* or based on this library. If you modify this library, you may extend
* this exception to your version of the library, but you are not
* obliged to do so. If you do not wish to do so, delete this
* exception statement from your version.
*/
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>
*/
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 == -1) ? -1 : 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;
}
// Fall through and return contents of buffer.
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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