cowos/kernel/klibc/stdio.c

#include <limits.h>
#include <stdarg.h>
/* #include <tty.h> */
#include <klibc/stdio.h>
#include <klibc/string.h>

/* returns 1 for true, adhering to suckless */
static int
print(const char* data, size_t length)
{
	const unsigned char* bytes = (const unsigned char*) data;
	for (size_t i = 0; i < length; i++) {
		if (putchar(bytes[i]) == EOF) {
			return 0;
                }
        }
	return 1;
}

/* todo: set errno to eoverflow for some cases in which errno should not be used */
int
printf(const char* restrict format, ...)
{
	va_list parameters;
	va_start(parameters, format);

	int written = 0;

	while (*format != '\0') {
		size_t maxrem = INT_MAX - written;

		if (format[0] != '%' || format[1] == '%') {
			if (format[0] == '%')
				format++;
			size_t amount = 1;
			while (format[amount] && format[amount] != '%')
				amount++;
			if (maxrem < amount) {
				return -1;
			}
			if (!print(format, amount))
				return -1;
			format += amount;
			written += amount;
			continue;
		}

		const char* format_begun_at = format++;

		if (*format == 'c') {
			format++;
			char c = (char) va_arg(parameters, int /* char promotes to int */);
			if (!maxrem) {
				return -1;
			}
			if (!print(&c, sizeof(c))) {
				return -1;
                        }
			written++;
		} else if (*format == 's') {
			format++;
			const char* str = va_arg(parameters, const char*);
			size_t len = strlen(str);
			if (maxrem < len) {
				return -1;
			}
			if (!print(str, len)) {
				return -1;
                        }
			written += len;
		} else {
			format = format_begun_at;
			size_t len = strlen(format);
			if (maxrem < len) {
				return -1;
			}
			if (!print(format, len)) {
				return -1;
                        }
			written += len;
			format += len;
		}
	}

	va_end(parameters);
	return written;
}

/* todo: Implement stdio and the write system call. */
int
putchar(int ic)
{
	return ic;
}

int
puts(const char* string)
{
        return printf("%s\n", string);
}