RandomAccessFileReader.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.apacheextras.simplearchive.impl;

import java.io.IOException;
import java.io.RandomAccessFile;
import java.io.Reader;
import java.nio.charset.StandardCharsets;


/**
 * Reader implementation which uses RandomAccessFile under the hood.
 * Attention, no concurrent usage is allowed!
 *
 * @author <a href="mailto:struberg@yahoo.de">Mark Struberg</a>
 */
public class RandomAccessFileReader extends Reader{

    private RandomAccessFile file;

    public RandomAccessFileReader(RandomAccessFile randomAccessFile) {
        this.file = randomAccessFile;
        try {
            file.seek(0);
        }
        catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    @Override
    public int read(char[] cbuf, int off, int len) throws IOException {
        byte[] bBuf = new byte[len - off];
        int bytesRead = file.read(bBuf);
        if (bytesRead <= 0) {
            return -1;
        }
        String s = new String(bBuf, StandardCharsets.UTF_8);
        char[] cRead = s.toCharArray();
        int i = 0;
        while (i < len) {
            if (i == cRead.length || cRead[i] == '\u0000') {
                break;
            }

            cbuf[off + i] = cRead[i];

            // continue with the next char
            i++;
        }

        return i;
    }

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

This is a simple Reader for java.nio.RandomAccessFile.

Sample usage is

        BufferedReader br = new BufferedReader(new RandomAccessFileReader(file), BUFFER_SIZE);
        String line = br.readLine();

This is needed as RandomAccessFile#readLine() reads byte-by-byte - how mad is that?