src/main/java/org/apache/maven/shared/filtering/BoundedReader.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.maven.shared.filtering;

import java.io.IOException;
import java.io.Reader;

/**
 * A reader that imposes a limit to the number of bytes that can be read from an underlying reader, simulating eof when
 * this limit is reached. This stream can typically be used to constrain a client with regard to a readAheadLimit of an
 * underlying stream, to avoid overrunning this limit and hence lose the opportunity do to reset.
 */
public class BoundedReader extends Reader {

    private final Reader target;

    int pos = 0;

    int readAheadLimit;

    /**
     * @param target {@link Reader}
     * @param readAheadLimit read ahead limit.
     * @throws IOException in case of a failure.
     */
    public BoundedReader(Reader target, int readAheadLimit) throws IOException {
        this.target = target;
        target.mark(readAheadLimit);
        this.readAheadLimit = readAheadLimit;
    }

    @Override
    public void close() throws IOException {
        target.close();
    }

    @Override
    public void reset() throws IOException {
        pos = 0;
        target.reset();
    }

    @Override
    public void mark(int theReadAheadLimit) throws IOException {
        this.readAheadLimit = theReadAheadLimit;
        target.mark(theReadAheadLimit);
    }

    @Override
    public int read() throws IOException {
        if (pos >= readAheadLimit) {
            return -1;
        }
        pos++;
        return target.read();
    }

    @Override
    public int read(char[] cbuf, int off, int len) throws IOException {
        int c;
        for (int i = 0; i < len; i++) {
            c = read();
            if (c == -1) {
                return i;
            }
            cbuf[off + i] = (char) c;
        }
        return len;
    }
}