from const char to char

Hi All

I'm writing a tool that uses C libraries.

Which means that I have to convert strings into 'const char*'s

So, this is how I think a string is converted into a char:

Code:

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const char* c = x.c_str ;

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The problem I have now is that my C library functions need a char* not a const char*..

Any suggestions what the best way is to go from a string to a char* ?

Thanks a lot
LuCa

You should copy over the characters (anyway).

Quote:

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string to a char*

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strcpy() will make a copy that you can alter.

If the size of the string is variable, you will probably need a variable length character array. In that case, use a vector so that it will handle memory management for you. Then pass the vector to the code that expects a char*:

Code:

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string s = "Some string.";
vector<char> buf(s.begin(), s.end());
buf += '\0';
SomeCFunction(&buf[0], s.size()); // SomeCFunction takes a char* and an int size.

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That code isn't tested, but should be basically correct.

(See 7stud's post below for corrections.)

Nice. I was trying to figure out how to handle the problem of variable lengths. Here's a tested version of Daved's solution:

Code:

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void someCFunction(char* str)
{
        cout<<str<<endl;
}

int main ()
{
        string s = "Some string.";
        vector<char> buf(s.begin(), s.end());
        buf.push_back('\0');
       
        someCFunction(&buf[0]);

        return 0;
}

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thanks a lot, this is all I need!!

The vector seems perfect!

LuCa

I guess this would be a better test:

Code:

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void changeIt(char* str)
{
        str[0] = 'X';
}

int main ()
{
        string s = "Some string.";
        vector<char> buf(s.begin(), s.end());
        buf.push_back('\0');
       
        changeIt(&buf[0]);
        cout<<&buf[0]<<endl;

        return 0;
}

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