Bit transposing

This is a discussion on Bit transposing within the C++ Programming forums, part of the General Programming Boards category; Hello, i was wondering on how to do a bit transposition. I really need this for a project i am ...

  1. #1
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    Nov 2003
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    Bit transposing

    Hello,
    i was wondering on how to do a bit transposition.
    I really need this for a project i am doing encrypting a data base.
    and i am stumped on this one.
    all help is appreciated
    thanks

  2. #2
    mustang benny bennyandthejets's Avatar
    Join Date
    Jul 2002
    Posts
    1,401
    You can determine whether or not a particular bit is turned on by using the & operator, ie:
    Code:
    if (value & 0x01)
    if (value & 0x02)
    if (value & 0x04)
    
    if (value & pow(2,0))
    if (value & pow(2,1))
    if (value & pow(2,2))
    To ensure a bit is turned on, do this:
    Code:
    value|=0x01;
    To ensure it is off, do this:
    Code:
    value&=~(0x01);
    Note that those last two code pieces will ensure the bit state no matter what it was orginally, so they're safe to use without first checking the state.

    I suggest a function signature like this:
    Code:
    int SwapBits(int value, int index1,int index2);
    Good luck. Have a shot, then post any problems you have.
    benforbes@optusnet.com.au
    Microsoft Visual Studio .NET 2003 Enterprise Architect
    Windows XP Pro

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