public static long toLong(byte[] bytes, int offset) {
    return toLong(bytes, offset, SIZEOF_LONG);
  }
Converts a byte array to a long value. Assumes there will be {@link #SIZEOF_LONG} bytes
available.
@param bytes  bytes
@param offset offset
@return the long value
hbase-common/src/main/java/org/apache/hadoop/hbase/util/Bytes.java