private static byte [ ] expandHrp ( final String hrp ) { int hrpLength = hrp . length ( ) ; byte ret [ ] = new byte [ hrpLength * 2 + 1 ] ; for ( int i = 0 ; i < hrpLength ; ++ i ) { int c = hrp . charAt ( i ) & 0x7f ; // Limit to standard 7-bit ASCII ret [ i ] = ( byte ) ( ( c >>> 5 ) & 0x07 ) ; ret [ i + hrpLength + 1 ] = ( byte ) ( c & 0x1f ) ; } ret [ hrpLength ] = 0 ; return ret ; }
Expand a HRP for use in checksum computation .