@Override
  public int hashCode() {
    long value = getAddress();
    return (int) (value ^ (value >>> 32));
  }
A fragment is a block of memory that can have chunks allocated from it. The allocations are
always from the front so the free memory is always at the end. The freeIdx keeps track of the
first byte of free memory in the fragment. The base memory address and the total size of a
fragment never change. During defragmentation fragments go away and are recreated.
geode-core/src/main/java/org/apache/geode/internal/offheap/Fragment.java