4 files changed, 40 insertions, 7 deletions
diff --git a/lib/stdio.h b/lib/stdio.h
index cf3a33f..201cce1 100644
--- a/lib/stdio.h
+++ b/lib/stdio.h
@@ -1,3 +1,6 @@
 #pragma once
 
+/**
+ * Supports %s (string), %d (decimal), %u (unsigned), %x (hexadecimal)
+ */
 int printf(const char *restrict format, ...);
diff --git a/lib/stdio/printf.c b/lib/stdio/printf.c
index f6b8ef6..269b9b6 100644
--- a/lib/stdio/printf.c
+++ b/lib/stdio/printf.c
@@ -1,8 +1,11 @@
 #include <stdarg.h>
 #include <stdio.h>
+#include <string.h>
 
 #include <devices/uart_16550.h>
 
+static char buffer[3 * sizeof(int) + 2];
+
 int
 printf(const char *restrict format, ...)
 {
@@ -22,6 +25,15 @@ printf(const char *restrict format, ...)
       case 's':
         written += uart_puts(COM1, va_arg(params, const char *), -1);
         break;
+      case 'd':
+        written += uart_puts(COM1, itoa(buffer, va_arg(params, int), 10), -1);
+        break;
+      case 'u':
+        written += uart_puts(COM1, utoa(buffer, va_arg(params, unsigned int), 10), -1);
+        break;
+      case 'x':
+        written += uart_puts(COM1, utoa(buffer, va_arg(params, unsigned int), 16), -1);
+        break;
       }
 
       l = 0;
diff --git a/lib/string.h b/lib/string.h
index 361d308..9873362 100644
--- a/lib/string.h
+++ b/lib/string.h
@@ -1,3 +1,4 @@
 #pragma once
 
-char *itoa(char *p, unsigned x);
+char *itoa(char *p, int x, int base);
+char *utoa(char *p, unsigned x, int base);
diff --git a/lib/string/itoa.c b/lib/string/itoa.c
index 5eefb37..3708be2 100644
--- a/lib/string/itoa.c
+++ b/lib/string/itoa.c
@@ -1,13 +1,30 @@
-#include "string.h"
+#include <stdbool.h>
+#include <string.h>
+
+static const char *numbers = "0123456789abcdef";
+
+char *
+itoa(char *p, int x, int base)
+{
+  const bool is_negative = (x < 0);
+  if (is_negative) x = -x;
+
+  p = utoa(p, x, base);
+
+  if (is_negative) *--p = '-';
+  return p;
+}
 
 char *
-itoa(char *p, unsigned x)
+utoa(char *p, unsigned x, int base)
 {
-  p += 3 * sizeof(int);
-  *--p = 0;
+  p += 3 * sizeof(unsigned);
+  *--p = '\0';
+
   do {
-    *--p = '0' + x % 10;
-    x /= 10;
+    *--p = numbers[x % base];
+    x /= base;
   } while (x);
+
   return p;
 }