Exercise 7.03

Page 156

Revise minprintf to handle more of the other facilities of printf.

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

int minprintf(char *fmt, ...)
{
	va_list ap;
	char *p, *sval;
	int ival;
	double dval;
	int extra_printed = 0;

	va_start(ap, fmt);
	for (p = fmt; *p; p++) {
		if (*p != '%') {
			putchar(*p);
			continue;
		}
		switch (*++p) {
		case 'c':
		case 'd':
		case 'i':
			ival = va_arg(ap, int);
			extra_printed = printf("%d", ival) - 1;
			break;
		case 'e':
		case 'E':
			dval = va_arg(ap, double);
			extra_printed = printf("%e", dval) - 1;
			break;
		case 'f':
			dval = va_arg(ap, double);
			extra_printed = printf("%f", dval) - 1;
			break;
		case 'g':
		case 'G':
			dval = va_arg(ap, double);
			extra_printed = printf("%g", dval) - 1;
			break;
		case 's':
			for (sval = va_arg(ap, char *); *sval;
			     sval++, extra_printed++) {
				putchar(*sval);
			}
			extra_printed -= 1;
			break;
		case 'u':
			ival = va_arg(ap, int);
			extra_printed = printf("%u", ival) - 1;
			break;
		case 'x':
		case 'X':
			ival = va_arg(ap, int);
			extra_printed = printf("%x", ival) - 1;
			break;
		default:
			putchar(*p);
			break;
		}
	}
	va_end(ap);

	return p - fmt + extra_printed;
}

int main()
{
	int printed = printf("%g\n", 123.456);
	printf("%d\n", printed);
}