/*
* This file is part of muCommander, http://www.mucommander.com
* Copyright (C) 2002-2016 Maxence Bernard
*
* muCommander 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 3 of the License, or
* (at your option) any later version.
*
* muCommander 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 program. If not, see <http://www.gnu.org/licenses/>.
*/
package com.mucommander.commons.io;
import java.io.FilterReader;
import java.io.IOException;
import java.io.Reader;
/**
* A <code>Reader</code> that has a set limit to the number of characters that can be read from it before the EOF
* is reached. The limit has no effect if it is set higher than the number of characters remaining in the
* underlying reader.
*
* @author Maxence Bernard
* @see StreamOutOfBoundException
*/
public class BoundedReader extends FilterReader {
private long totalRead;
private long allowedCharacters;
private IOException outOfBoundException;
/**
* Equivalent to {@link #BoundedReader(java.io.Reader, long, java.io.IOException)} called with a
* <code>null</code> <code>IOException</code>.
*
* @param reader the reader to limit
* @param allowedCharacters the total number of characters this reader allows to be read or skipped, <code>-1</code>
* for no limitation
*/
public BoundedReader(Reader reader, long allowedCharacters) {
this(reader, allowedCharacters, null);
}
/**
* Creates a new <code>BounderReader</code> over the specified reader, allowing a maximum of
* <code>allowedCharacters</code> to be read or skipped. If <code>allowedCharacters</code> is equal to <code>-1</code>,
* this reader is not bounded and acts as a normal stream.
* <p>
* The specified <code>IOException</code> will be thrown when an attempt to read or skip beyond that is made.
* If it is <code>null</code>, read and skip methods will return <code>-1</code> instead of throwing an
* <code>IOException</code>.
* </p>
*
* @param reader the reader to bind
* @param allowedCharacters the total number of characters this reader allows to be read or skipped, <code>-1</code>
* for no limitation
* @param outOfBoundException the IOException to throw when an attempt to read or skip beyond <code>allowedBytes</code>
* is made, <code>null</code> to return -1 instead
* @see StreamOutOfBoundException
*/
public BoundedReader(Reader reader, long allowedCharacters, IOException outOfBoundException) {
super(reader);
this.allowedCharacters = allowedCharacters;
this.outOfBoundException = outOfBoundException;
}
/**
* Returns the total number of characters that this reader allows to be read, <code>-1</code> is this reader is
* not bounded.
*
* @return the total number of characters that this reader allows to be read, <code>-1</code> is this reader is
* not bounded
*/
public long getAllowedCharacters() {
return allowedCharacters;
}
/**
* Returns the total number of characters that have been read or skipped thus far.
*
* @return the total number of characters that have been read or skipped thus far
*/
public synchronized long getReadCounter() {
return totalRead;
}
/**
* Returns the remaining number of characters that this reader allows to be read, {@link Long#MAX_VALUE} if this
* reader is not bounded.
*
* @return the remaining number of characters that this reader allows to be read, {@link Long#MAX_VALUE} if this
* reader is not bounded.
*/
public synchronized long getRemainingCharacters() {
return allowedCharacters<=-1 ? Long.MAX_VALUE : allowedCharacters-totalRead;
}
///////////////////////////
// Reader implementation //
///////////////////////////
@Override
public synchronized int read(char[] cbuf, int off, int len) throws IOException {
int canRead = (int)Math.min(getRemainingCharacters(), len);
if(canRead==0) {
if(outOfBoundException==null)
return -1;
throw outOfBoundException;
}
int nbRead = in.read(cbuf, off, canRead);
if(nbRead>0)
totalRead += nbRead;
return nbRead;
}
////////////////////////
// Overridden methods //
////////////////////////
@Override
public synchronized int read() throws IOException {
if(getRemainingCharacters()==0) {
if(outOfBoundException==null)
return -1;
throw outOfBoundException;
}
int i = in.read();
totalRead++;
return i;
}
@Override
public synchronized long skip(long n) throws IOException {
int canSkip = (int)Math.min(getRemainingCharacters(), n);
if(canSkip==0) {
if(outOfBoundException==null)
return -1;
throw outOfBoundException;
}
long nbSkipped = in.skip(canSkip);
if(nbSkipped>0)
totalRead += nbSkipped;
return nbSkipped;
}
/**
* Always returns <code>false</code>, even if the underlying reader supports it.
*
* @return always returns <code>false</code>, even if the underlying reader supports it
*/
@Override
public boolean markSupported() {
// Todo: in theory we could support mark/reset
return false;
}
/**
* Implemented as a no-op: the call is *not* delegated to the underlying reader.
*/
@Override
public synchronized void mark(int readlimit) {
// Todo: in theory we could support mark/reset
// No-op
}
/**
* Always throws an <code>IOException</code>: the call is *not* delegated to the underlying reader.
*/
@Override
public synchronized void reset() throws IOException {
// Todo: in theory we could support mark/reset
// No-op
}
}