wm: teppich

ref: 723dcdf945237c6fa70e4f964cfce71d963ec90f
dir: /libc/printf.c/

#include <u.h>
#include <libc.h>

int
print_char(int c)
{
	return vga_putc(c);
}

int
print_str(char *str)
{

	vga_puts(str);

	return strlen(str);
}

int
print_digit(long num, int base)
{
	int count;
	char* symbols = "0123456789abcdef";

	if (num < 0)
	{
		vga_puts("-");
		return print_digit(-num, base) + 1;
	}
	else if (num < base)
	{
		return print_char(symbols[num]);
	}
	else
	{
		count = print_digit(num / base, base);
		return count + print_digit(num % base, base);
	}
	
}

int
print_format(char specifier, va_list ap)
{
	int count = 0;

	switch (specifier)
	{
	case 'c':
		count += print_char(va_arg(ap, int));	// Type promotion
		break;
	case 's':
		count += print_str(va_arg(ap, char*));
		break;
	case 'd':
		count += print_digit((long)va_arg(ap, int), 10);
		break;
	case 'x':
		count += print_digit((long)va_arg(ap, unsigned int), 16);
	default:
		count += vga_puts(specifier);
		break;
	}

	return count;
}

int
printf(const char* restrict format, ...) 
{
	va_list ap;
	va_start(ap, format);
	int count = 0;

	while (*format) 
	{
		if (*format == '%') 
			count += print_format(*(++format), ap);
		else 
			count += vga_putc(format);
		format++;
	}

	va_end(ap);
	return count;
}