001/****************************************************************
002 * Licensed to the Apache Software Foundation (ASF) under one   *
003 * or more contributor license agreements.  See the NOTICE file *
004 * distributed with this work for additional information        *
005 * regarding copyright ownership.  The ASF licenses this file   *
006 * to you under the Apache License, Version 2.0 (the            *
007 * "License"); you may not use this file except in compliance   *
008 * with the License.  You may obtain a copy of the License at   *
009 *                                                              *
010 *   http://www.apache.org/licenses/LICENSE-2.0                 *
011 *                                                              *
012 * Unless required by applicable law or agreed to in writing,   *
013 * software distributed under the License is distributed on an  *
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY       *
015 * KIND, either express or implied.  See the License for the    *
016 * specific language governing permissions and limitations      *
017 * under the License.                                           *
018 ****************************************************************/
019
020package org.apache.james.mime4j.io;
021
022import java.io.InputStream;
023import java.io.IOException;
024
025public class LimitedInputStream extends PositionInputStream {
026
027    private final long limit;
028
029    public LimitedInputStream(InputStream instream, long limit) {
030        super(instream);
031        if (limit < 0) {
032            throw new IllegalArgumentException("Limit may not be negative");
033        }
034        this.limit = limit;
035    }
036
037    private void enforceLimit() throws IOException {
038        if (position >= limit) {
039            throw new IOException("Input stream limit exceeded");
040        }
041    }
042
043    @Override
044    public int read() throws IOException {
045        enforceLimit();
046        return super.read();
047    }
048
049    @Override
050    public int read(byte b[], int off, int len) throws IOException {
051        enforceLimit();
052        len = Math.min(len, getBytesLeft());
053        return super.read(b, off, len);
054    }
055
056    @Override
057    public long skip(long n) throws IOException {
058        enforceLimit();
059        n = Math.min(n, getBytesLeft());
060        return super.skip(n);
061    }
062
063    private int getBytesLeft() {
064        return (int)Math.min(Integer.MAX_VALUE, limit - position);
065    }
066
067}