@Override
      int putLong(byte[] bytes, int offset, long val) {
        for (int i = offset + 7; i > offset; i--) {
          bytes[i] = (byte) val;
          val >>>= 8;
        }
        bytes[offset] = (byte) val;
        return offset + SIZEOF_LONG;
      }
Returns the Unsafe-using Converter, or falls back to the pure-Java implementation if unable
to do so.
hbase-common/src/main/java/org/apache/hadoop/hbase/util/Bytes.java