Thread: Creating Functions that use Format control Strings

Originally Posted by tzuchan

Is it possible to create functions that are similar to scanf in the sense that I can use a format control string to determine how many variables the function will take in?

eg:
new_function(const char*, var1, var2, var3,...);

if so, can anyone point me in the direction of where to look for more information regarding this?
(Or can anyone tell me where I can sneak a peek at the scanf functions to see how they work...)

Functions using variable numbers of parameters can be coded using the va_start, va_end, and va_arg functions that are declared in the stdio.h header.

http://www.cprogramming.com/tutorial/lesson17.html

Originally Posted by tzuchan

Err... Just looked through my stdio.h file...
Didn't find any of those functions...
I'm using the mingw32 compiler... Any ideas where else I should try looking?

Oops, sorry bout that. The required header appear to be stdarg.h or optionally varargs.h.

This doesn't really do much, but it's a start, anyway:

Code:

 int sprint(char buffer[], const char * first, ...)
{ 
 const char * fmt = first;
 
 char * b = buffer;
 
 char ch;
 
 va_list vap;
 
 va_start(vap, first);
  
     while(*fmt)
    {
     ch = *fmt++;
     
         if(ch == '%')
        {     
         ch = *fmt++;
                 
             if(ch == 's')
            {             
             char * vs = va_arg(vap, char*);

                 while(*vs)
                {
                 *b++ = *vs++;
                }
            }    
             else // ...not recognized...
            {
             --fmt;
            }          
        }
         else // ... just copy...
        {
         *b++ = ch;
        }     
    } 
 
 *b = 0;
 
 va_end(vap);
 
 return b - buffer;
}