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Variable arguments: creating an sprintf wrapper?

Started by Zorodius Feb 2, 2003 at 7:24 AM 4 replies 8k views

Original Post

Feb 2, 2003 at 7:24 AM

I''ve got a class that maintains an error log. Currently, if I want to record the value of some variable, I have to first declare an array to store a string, then use sprintf() to load that string with the data I want, then pass the string to my error-recording function. That''s not cool. Instead, it would be a lot better if my error-recording function worked similarilly to the sprintf() line of functions. However, I''m having a lot of trouble getting this to work. At the core of it, all I''m trying to do here is to create a wrapper function for sprintf. I''m including stdarg.h, and I''ve declared my function with the function(char * s, ...); syntax. However, I can''t figure out how to define that function so that it calls sprintf with the information it has been given. Is there any easy way to do this? Or am I going to have to write a function that performs the same string-parsing work as sprintf does?

Burning_Ice

Feb 2, 2003 at 7:36 AM

look into va_list, va_start and va_end
here''s some working code i use:

  
void tConsole::Print ( const char *msg, ... )
{
	va_list argList;
	char buffer[512] = { 0 };
	va_start(argList, msg);
	vsprintf(buffer, msg, argList);
	va_end(argList);

        // now buffer contains the formatted message..

        // do with it whatever you want :)


}

Runicsoft -- latest attraction: obfuscated Brainfuck Interpreter in SML

( This post was made entirely from re-cycled electrons )

Zorodius

Author

Zorodius

Feb 2, 2003 at 7:45 AM

Awesome, vsprintf was exactly what I was looking for. Thanks so much!

Qw3r7yU10p!

Feb 2, 2003 at 10:37 AM

on a side note you may be interested in boost''s format library

Void

129

Void

Feb 3, 2003 at 10:44 AM

Unless you are coding in C, I suggest you learn how to use C++ stringstreams instead.

The 512 char buffer is the main reason behind buffer overflows security exploits so commonly found these days.

SabreMan

127

SabreMan

Feb 3, 2003 at 10:53 AM

quote:
Original post by Zorodius
I''ve got a class that maintains an error log.
[...]
all I''m trying to do here is to create a wrapper function for sprintf. I''m including stdarg.h, and I''ve declared my function with the function(char * s, ...); syntax.

I''m reminded of this thread.

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