Passing data

This is a discussion on Passing data within the C Programming forums, part of the General Programming Boards category; Hello, Earlier today, I asked about how to allocate a big memory location. Thanks all! Now I have another problem, ...

  1. #1
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    Passing data

    Hello,

    Earlier today, I asked about how to allocate a big memory location. Thanks all! Now I have another problem, please help.
    I have a short program like this:

    int main(void) {
    CallFunction (datapassing1);
    CallFunction (datapassing2);
    .
    .
    return 0;
    }

    Where datapassing1 and datapassing2 are short programs that need a memory space of about 4kb to do some cratch work. I don't know how to pass the data, allocate the memory location for this datapassing. Anyone has any idea, please give me some advice. I really appreciate.

  2. #2
    Confused Magos's Avatar
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    Re: Passing data

    Originally posted by vnrabbit
    Where datapassing1 and datapassing2 are short programs that need a memory space of about 4kb to do some cratch work
    Do you mean functions?
    The fastest way would be to send the pointer to the data (only pass 4 bytes instead of 4k, or whatever).
    Code:
    void datapassing1(int* Data)
    {
       ... //Do whatever
    }
    
    void datapassing2(int* Data)
    {
       ... //Do whatever
    }
    
    int main(void)
    {
       int* Data; //Assume your data are integers
       Data = new int[SizeOfData]; //Allocate memory
       if(Data == NULL) return 0; //Check if allocation was successful
    
       ...
    
       CallFunction (datapassing1(Data));
       CallFunction (datapassing2(Data));
    
       delete[] Data; //Deallocate the memory
       return 0; 
    }
    MagosX.com

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  3. #3
    ATH0 quzah's Avatar
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    > Data = new int[SizeOfData]; //Allocate memory

    Slight correction. The above code is C++, not C. You'd want:

    Data = malloc( sizeof(int) * number_to_allocate ) );

    The same goes for the 'delete' call.

    Quzah.
    Hope is the first step on the road to disappointment.

  4. #4
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    Thanks guys.

    However, I can't change the datapassing1 and datapassing2 functions on the way I call them. Maybe I didnt explain my question clearly. When I call in the CallFunction() in Main, I then need to allocate a memory location about 4kb for datapassing1 and datapassing2 to do their stuff on this 4kb memory location.

  5. #5
    ATH0 quzah's Avatar
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    Code:
    void myFunction( void * data )
    {
        /* do something */
    }
    
    int main( void )
    {
        /*
            Allocate 4 KB of data.
        */
        void *dataBlock;
        dataBlock = malloc( 4096 );
    
        myFunction( dataBlock );
    
        return 0;
    }
    There's one way to allocate a 4KB block of data for use elsewhere. Naturally it's better to actually allocate specific types, but if you just want a solid 4K block of memory allocated for you, that'd do it.

    You could then dice that up or do whatever you intend with it.

    Quzah.
    Hope is the first step on the road to disappointment.

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