@Override
  public long getLongAfterPosition(int offset) {
    checkRefCount();
    // Mostly the index specified will land within this current item. Short circuit for that
    int index = offset + this.position();
    int itemIndex;
    if (this.itemBeginPos[this.curItemIndex + 1] > index) {
      itemIndex = this.curItemIndex;
    } else {
      itemIndex = getItemIndexFromCurItemIndex(index);
    }
    return getLong(index, itemIndex);
  }
Fetches the long at the given index. Does not change position of the underlying ByteBuffers
@return the long value at the given index
hbase-common/src/main/java/org/apache/hadoop/hbase/nio/MultiByteBuff.java