MemMappedMessageLogger.java

/*
 * Licensed 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.f1x.log.file.nio;

import org.f1x.log.MessageLog;

import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;

/**
 * Message logger that keeps last <code>maxSize</code> bytes of FIX traffic.
 * Fixed size logger backed by memory mapped file.
 */
public class MemMappedMessageLogger implements MessageLog {

    private final RandomAccessFile raf;
    private final MappedByteBuffer out;

    /**
     *
     * @param file
     * @param maxSize This setting defines maximum size of log file. Leave at zero to disable this feature.
     */
    public MemMappedMessageLogger (File file, int maxSize) {
        try {
            raf = new RandomAccessFile(file, "rw");
            out = raf.getChannel().map(FileChannel.MapMode.READ_WRITE, 0, maxSize);
        } catch (IOException e) {
            throw new RuntimeException("Error opening log file " + file.getAbsolutePath(), e);
        }
    }

    @Override
    public synchronized void log(boolean isInbound, byte[] buffer, int offset, int length) {

        final int remaining = out.remaining();
        if (remaining < length) {
            if (remaining > 0)
                out.put(buffer, offset, remaining);
            out.position(0);
            out.put(buffer, offset+remaining, length - remaining);
        } else {
            out.put(buffer, offset, length);
        }

        if (out.remaining() > 0)
            out.put((byte)'\n');

    }

    @Override
    public synchronized void close() throws IOException {
        out.force();
        raf.close();
    }
}