question: public static byte [ ] long2buff ( long n ) { byte [ ] bs ; bs = new byte [ 8 ] ; bs [ 0 ] = ( byte ) ( ( n > > 56 ) & 0xFF ) ; bs [ 1 ] = ( byte ) ( ( n > > 48 ) & 0xFF ) ; bs [ 2 ] = ( byte ) ( ( n > > 40 ) & 0xFF ) ; bs [ 3 ] = ( byte ) ( ( n > > 32 ) & 0xFF ) ; bs [ 4 ] = ( byte ) ( ( n > > 24 ) & 0xFF ) ; bs [ 5 ] = ( byte ) ( ( n > > 16 ) & 0xFF ) ; bs [ 6 ] = ( byte ) ( ( n > > 8 ) & 0xFF ) ; bs [ 7 ] = ( byte ) ( n & 0xFF ) ; return bs ; }
target:  long convert to buff (big-endian)