Simple stream::form() replacement

[Dmitry Samersoff <dms at samersoff dot net>]

Absence of stream::form and stream::vform functions in new libstdc++ 
really discurages me.

  I have lots of code using it and migration from gcc 2.95 to 3.0.4 
become a hard task.

Here is quick and simple replacement for it.

It missed some futures of real printf like floating point support, but 
can handle the most necessary things:
%*d, %04ld, %20s

I'm going to include better version to next release of libdms (see 
libdms.sourceforge.net) nearest future.

-- 
Dmitry Samersoff
dms@samersoff.net, http://devnull.wplus.net
ICQ: 3161705 irc://dalnet/samersoff
*There will come soft rains ...

/*
 * $id$
 *
 */

#include <stdarg.h>

using namespace std;
#include <iostream>
#include <iomanip>

ostream& sform(ostream& os, char *format, ... )
{
 char* fptr = format;
 va_list ap;
 va_start(ap, format);

 while(*fptr)
 {
   if (*fptr == '%')
      {
	    ++fptr; 

	   /* init state */ 
	    int width     = 0;
		int modifier  = 'i';
		int fill      = ' ';

		os << nouppercase; 

		// set zerro fill if necessary
		if (*fptr == '0')  
		{  fill = '0';
		  ++fptr;
		}

		// extract width from varg or from fromat
	    if (*fptr == '*') 
		{
			width = va_arg(ap, int);
			++ fptr;
		}
		else
		{
           for(; (*fptr >= '0' && *fptr <= '9'); ++fptr) 
              { width =width*10+(*fptr - '0'); 
              }
		}

		if (*fptr == 'l') // handle %lX && %ld
		{ modifier = 'l';
		  ++fptr;
		}

        switch(*fptr)
         {  
			case 'c':
			{ 	int c = va_arg(ap, int);
			    os << (char) c; 
			}
             break;
			case 's':
		    { 	char* s = va_arg(ap, char *);
			    if (width > 0) os << setw(width);
				os << s;
			 }
             break;
			case 'd' :
			{  	if (width > 0) os << setw(width);
			    os << setfill( (char) fill);  
				os << dec;
				if (modifier == 'l')
				{
					long ld = va_arg(ap, long);
					os << ld;
				}
				else if (modifier == 'i')
				{
					int id = va_arg(ap, int);
					os << id;
				}
			}
             break;
			case 'X' :
				os << uppercase; 
			case 'x' :
			{	if (width > 0) os << setw(width);
			    os << setfill( (char) fill);  
			   	os << hex;
			   	if (modifier == 'l')
			   	{
			   		long ld = va_arg(ap, long);
			   		os << ld;
			   	}
			   	else if (modifier == 'i')
			   	{
			   		int id = va_arg(ap, int);
			   		os << id;
			   	}
			}
             break;
         } 

        ++fptr;		// don't copy format characters
      } // if %

      os << (char) *fptr;
     ++fptr;
 } // while

 return os;
} 


int main(void)
{
	sform(cerr, "%s: %04lX %s\n", "NUMBER", 12, "ok" );
}