this is an inline macro definitions

any time someone writes in the code S1(x) then it is subsituted with (((x&2)>>1) | ((x&1)<<2))

in order to implement it in vb.net (if there are no macros) you can just write a method that does the exact same thing and call it everytime you see the S1(x) text in the code

the & is an and bit operation,

the >> and << are shifting the bits right and left,

if you don't have a shifting operation in vb you can just multiply be a power of 2

shift left (<<) by x is the same as multiply by 2 in the power of x

shift right (>>) by x is the same as dividing by 2 in the power of x

momi sabag