how can I handle a buffer???

This is a discussion on how can I handle a buffer??? within the C++ Programming forums, part of the General Programming Boards category; Hi there....\n\n Suppose we have a pointer if void type which we use then to allocate memory and create a ...

  1. #1
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    Unhappy how can I handle a buffer???

    Hi there....\n\n

    Suppose we have a pointer if void type which we use then to allocate memory and create a buffer....

    the buffer ,lets say has at first a string of 10 chars then a float and then and integer....


    How I can access and print the fields of it?

    My thought was to use a second pointer and allocate memory to him so it can hold the proper field and then copy on him the data but it does not work....


    Whats wrong?

    I thank "apriori" anyone for his good mood of helping me....

  2. #2
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    Greetings,

    You could use a union, for example:

    Code:
    #include <iostream>
    
    // This structure will hold a string/int/float element
    struct element {
        int type              // This will allow us to know what we have
        union {
            char* str;
            int   i;
            float f;
        };
    };
    
    int main() 
    {
        element *elarray = new element [4];
        element e;
    
        // Im using 0=String; 1=Integer; 2=Float
        e.type = 0;
        e.str = new char [10];
        strcpy(e.str, "Testing");
        elarray[0] = e;                     // Set the 1st element
    
        e.type = 1;                          // This one is an int
        e.i = 1000;	
        elarray[1] = e;
    
        e.type = 2;                          // And this one a float
        e.f = 5.5f;
        elarray[2] = e;
    
        // Loop through the array displaying the type and value of
        // the element
        std::cout << "Type\t\tValue\n";
        for (int i=0;i<3;i++) {
            switch(elarray[i].type) {
                case 0:
                    std::cout << "String\t\t" << elarray[i].str << std::endl;
                    break;
                case 1:
                    std::cout << "Integer\t\t" << elarray[i].i << std::endl;
                    break;
                case 2:
                    std::cout << "Float\t\t" << elarray[i].f << std::endl;
                    break;
            }
        }
        delete [] elarray;
    }
    This works, but if you want a much more elegant and functional solution you should take a look at www.boost.org look at the file "any.hpp".

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