add basic stdio

src/isr.c

@@ -44,7 +44,7 @@ void isr_install() {
 void isr0()
 {
     terminal_writestring(exception_messages[0]);
-    asm("hlt");    
+    asm("hlt");
 }
 void isr1()
 {

src/kernel.c

@@ -1,5 +1,6 @@
 #include "../include/isr.h"
 #include "../include/screen.h"
+#include "../include/stdio.h"
 #include "../include/utils.h"
 
 /* Check if the compiler thinks you are targeting the wrong operating system. */
@@ -16,9 +17,12 @@
 void kmain()
 {
 	terminal_initialize();
-	terminal_writestring("KatauOS booting up\n");
+	printf("KatauOS booting up\n");
 	isr_install();
-	terminal_writestring("Kernel init sequence completed\n");
+	printf("Kernel init sequence completed\n");
+
+	char yooo[256] = "heheh";
+	printf("test string: %s\n", yooo);
 
 	while(1)
 	{

src/stdio.c

@@ -0,0 +1,99 @@
+#include "../include/stdio.h"
+#include <stdbool.h>
+#include <stdarg.h>
+#include <stddef.h>
+#include "../include/string.h"
+
+#ifdef __is_katauos
+#include "../include/screen.h"
+#endif
+
+int puts(const char* string) {
+	return printf("%s\n", string);
+}
+
+int putchar(int ic) {
+#if defined(__is_katauos)
+	char c = (char) ic;
+	terminal_write(&c, sizeof(c));
+#else
+	// TODO: Implement stdio and the write system call.
+#endif
+	return ic;
+}
+
+
+static bool 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 false;
+	return true;
+}
+
+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) {
+				// TODO: Set errno to EOVERFLOW.
+				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) {
+				// TODO: Set errno to EOVERFLOW.
+				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) {
+				// TODO: Set errno to EOVERFLOW.
+				return -1;
+			}
+			if (!print(str, len))
+				return -1;
+			written += len;
+		} else {
+			format = format_begun_at;
+			size_t len = strlen(format);
+			if (maxrem < len) {
+				// TODO: Set errno to EOVERFLOW.
+				return -1;
+			}
+			if (!print(format, len))
+				return -1;
+			written += len;
+			format += len;
+		}
+	}
+
+	va_end(parameters);
+	return written;
+}