c/c++ Arugment List

[zappa86]

How can I creating a function like printf that cant take unlimited arguments. I want to make a functing called Logger_Print and have it do what printf would basically do and more. I know you need to do something with the ... inorder to make it take many arguments.

void Logger_Print(int Type, char *Text, ... /*Hopefully a list of arguments */) {
	switch(Type) {
		case 0:
			fprintf(Logger_OutFile, "Verbose: ");
			break;
		case 1:
			fprintf(Logger_OutFile, "Status: ");
			break;
		case 2:
			fprintf(Logger_OutFile, "Notice: ");
			break;
	}

	fprintf(Logger_OutFile, Text, /* The list of arguments passed to this function */);
}

Please let me know if you know how to add the argument list for the Logger_Print to the fprintf call in the function. Thanks.

 

[1tbs4life]

How can I creating a function like printf that cant take unlimited arguments.

Here's a good place to read up on variable argument lists. Here's a quick example I wrote showing how to use them:

#include <stdio.h>
#include <stdarg.h>

void print(int n, ...);

int main() {
    print(10, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
}

void print(int n, ...) {
    int i;
    va_list va;
    
    va_start(va, n);
    for (i = 0; i < n; ++i)
        printf("%d ", va_arg(va, int));
    
    va_end(va);
}

Please let me know if you know how to add the argument list for the Logger_Print to the fprintf call in the function. Thanks.

Honestly, I don't know if it is possible to carry out everything in Logger_Print() using your strategy. For you see, va_arg() must be called every time you want to fetch an argument from the variable argument list, and printf() itself must be passed all of the variables at once.

 

[mikeblas]

just use vfprintf. I used vprintf here because I didn't want to cook up a file handle for an example:

void Logger_Print(int Type, char *Text, ... /*Hopefully a list of arguments */) {
	switch(Type) {
		case 0:
			printf( "Verbose: ");
			break;
		case 1:
			printf("Status: ");
			break;
		case 2:
			printf("Notice: ");
			break;
	}

	va_list valist;
	va_start(valist, Text);
	vprintf(Text, valist);
}

int main(int argc, char* argv[])
{
	Logger_Print(0, "%d, %d", 3, 5);
	return 0;
}