package com.codecademy.eventhub.list;
import com.google.inject.AbstractModule;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
public class DmaIdListModule extends AbstractModule {
@Override
protected void configure() {
bind(DmaIdList.Factory.class).to(DmaIdListFactory.class);
}
private static class DmaIdListFactory implements DmaIdList.Factory {
private int defaultCapacity;
private DmaIdListFactory() {
this.defaultCapacity = 10;
}
@Override
public void setDefaultCapacity(int defaultCapacity) {
this.defaultCapacity = defaultCapacity;
}
@Override
public DmaIdList build(String filename) {
try {
File file = new File(filename);
if (!file.exists()) {
//noinspection ResultOfMethodCallIgnored
file.getParentFile().mkdirs();
//noinspection ResultOfMethodCallIgnored
file.createNewFile();
try (RandomAccessFile raf = new RandomAccessFile(new File(filename), "rw")) {
raf.setLength(DmaIdList.META_DATA_SIZE + defaultCapacity * DmaIdList.SIZE_OF_DATA);
}
}
try (RandomAccessFile raf = new RandomAccessFile(new File(filename), "rw")) {
FileChannel channel = raf.getChannel();
MappedByteBuffer buffer = channel.map(FileChannel.MapMode.READ_WRITE, 0, raf.length());
int numRecords = buffer.getInt();
int capacity = (int) (raf.length() - DmaIdList.META_DATA_SIZE) / DmaIdList.SIZE_OF_DATA;
buffer.position(DmaIdList.META_DATA_SIZE + numRecords * DmaIdList.SIZE_OF_DATA);
return new DmaIdList(filename, buffer, numRecords, capacity);
}
} catch (IOException e) {
throw new RuntimeException(e);
}
}
}
}