implement %x in printf

core/klibc.c

@@ -17,3 +17,41 @@ void *memset(void *src, int c, size_t n)
         }
         return src;
 }
+
+char * itoa( int value, char * str, int base )
+{
+    char * rc;
+    char * ptr;
+    char * low;
+    // Check for supported base.
+    if ( base < 2 || base > 36 )
+    {
+        *str = '\0';
+        return str;
+    }
+    rc = ptr = str;
+    // Set '-' for negative decimals.
+    if ( value < 0 && base == 10 )
+    {
+        *ptr++ = '-';
+    }
+    // Remember where the numbers start.
+    low = ptr;
+    // The actual conversion.
+    do
+    {
+        // Modulo is negative for negative value. This trick makes abs() unnecessary.
+        *ptr++ = "zyxwvutsrqponmlkjihgfedcba9876543210123456789abcdefghijklmnopqrstuvwxyz"[35 + value % base];
+        value /= base;
+    } while ( value );
+    // Terminating the string.
+    *ptr-- = '\0';
+    // Invert the numbers.
+    while ( low < ptr )
+    {
+        char tmp = *low;
+        *low++ = *ptr;
+        *ptr-- = tmp;
+    }
+    return rc;
+}

core/klibc.h

@@ -1,5 +1,6 @@
 #pragma once
 #include "stdarg.h"
 
-void *memcpy(void *dest, const void *src, size_t n );
+void *memcpy(void *dest, const void *src, size_t n);
 void *memset(void *s, int c, size_t n);
+char *itoa(int value, char *str, int base);

drivers/vga.c

@@ -104,6 +104,13 @@ void vprintf(const char *format, va_list ap)
 						printInt(d);
 						break;
 					}
+					case 'x': {
+						char val[sizeof(int) * 2];
+						int d = va_arg(ap, int);
+						itoa(d, val, 16);
+						printString(val);
+						break;
+					}
 					case 'c': {
 						int c = va_arg(ap, int);
 						printChar((char)c);