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C to VB.Net conversion

Posted on 2006-10-29
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Last Modified: 2010-04-15
Hi,

I'm trying to convert some C code into VB.Net, can anyone explain in simple terms the code below?

Thank you.

#define S1(a) (((a&2)>>1) | ((a&1)<<2))
#define S2(a) (((a&2)>>0) | ((a&1)<<3))
#define S3(a) (((a&2)>>1) | ((a&1)<<2))
#define S4(a) (((a&2)>>0) | ((a&1)<<3))
#define S5(a) (((a&2)>>1) | ((a&1)<<2))
#define S6(a) (((a&2)>>0) | ((a&1)<<3))
#define S7(a) a
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Question by:IAJWDDIY
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7 Comments
 
LVL 37

Assisted Solution

by:momi_sabag
momi_sabag earned 400 total points
ID: 17828749
hi

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
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Author Comment

by:IAJWDDIY
ID: 17828865
So if I write in the code S1(1) then would it be subsituted with (((1&2)>>1) | ((1&1)<<2))

Thank you.
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LVL 48

Accepted Solution

by:
AlexFM earned 100 total points
ID: 17828893
   Function S1(ByVal a As Integer) As Integer
        Return ((a And 2) >> 1) Or ((a And 1) << 2)
    End Function
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LVL 48

Expert Comment

by:AlexFM
ID: 17828904
Make other functions by the same way. The simplest case is S7:

   Function S7(ByVal a As Integer) As Integer
        Return a
    End Function

You can write function with two additioal parameters if you want, but writing functions S1-S7 allows to translate C code to VB easily, which looks better.
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LVL 37

Expert Comment

by:momi_sabag
ID: 17828910
the answer for your question is yes
s1(1) would be subsituted with (((1&2)>>1) | ((1&1)<<2))
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Author Comment

by:IAJWDDIY
ID: 17828952
Thank you both, much appreciated !
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Author Comment

by:IAJWDDIY
ID: 17828956
Sorry just noticed I got the Accepted/Assisted the wrong way round, hope I got the points right.
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