java内存缓冲区类

public class MemoryBuffer {
  // getting Unsafe by reflection
  public static final Unsafe unsafe = UnsafeUtil.getUnsafe();

  private final byte[] buffer;

  private static final long byteArrayOffset = unsafe.arrayBaseOffset(byte[].class);
  private static final long longArrayOffset = unsafe.arrayBaseOffset(long[].class);
  /* other offsets */

  private static final int SIZE_OF_LONG = 8;
  /* other sizes */

  private long pos = 0;

  public MemoryBuffer(int bufferSize) {
    this.buffer = new byte[bufferSize];
  }

  public final byte[] getBuffer() {
    return buffer;
  }

  public final void putLong(long value) {
    unsafe.putLong(buffer, byteArrayOffset + pos, value);
    pos += SIZE_OF_LONG;
  }

  public final long getLong() {
    long result = unsafe.getLong(buffer, byteArrayOffset + pos);
    pos += SIZE_OF_LONG;
    return result;
  }

  public final void putLongArray(final long[] values) {
    putInt(values.length);
    long bytesToCopy = values.length << 3;
    unsafe.copyMemory(values, longArrayOffset, buffer, byteArrayOffset + pos, bytesToCopy);
    pos += bytesToCopy;
  }


  public final long[] getLongArray() {
    int arraySize = getInt();
    long[] values = new long[arraySize];
    long bytesToCopy = values.length << 3;
    unsafe.copyMemory(buffer, byteArrayOffset + pos, values, longArrayOffset, bytesToCopy);
    pos += bytesToCopy;
    return values;
  }

  /* other methods */
}