stdio: add intToString and make use of it in printf

src/gdt.c

@@ -68,7 +68,7 @@ void create_descriptor(uint32_t base, uint32_t limit, uint16_t flag)
     descriptor |= base  << 16;                       // set base bits 15:0
     descriptor |= limit  & 0x0000FFFF;               // set limit bits 15:0
  
-    printf("0x%.16llX\n", descriptor);
+    printf("GDT descriptor 0x%X flag: 0x%X\n", descriptor, flag);
 }
 
 void gdt_install()

src/stdio.c

@@ -22,6 +22,52 @@ int putchar(int ic) {
 	return ic;
 }
 
+void intToString(int value, char *buffer, char format) {
+    int i = 0;
+    int isNegative = 0;
+    unsigned int uValue;
+
+    if (format == 'd') {
+        if (value < 0) {
+            isNegative = 1;
+            uValue = -value;
+        } else {
+            uValue = value;
+        }
+
+        do {
+            buffer[i++] = '0' + (uValue % 10);
+            uValue /= 10;
+        } while (uValue > 0);
+
+        if (isNegative) {
+            buffer[i++] = '-';
+        }
+    } else if (format == 'x' || format == 'X') {
+        uValue = (unsigned int)value;
+
+        do {
+            int digit = uValue % 16;
+            if (digit < 10) {
+                buffer[i++] = '0' + digit;
+            } else {
+                buffer[i++] = (format == 'x') ? ('a' + digit - 10) : ('A' + digit - 10);
+            }
+            uValue /= 16;
+        } while (uValue > 0);
+    } else {
+        buffer[0] = '\0';
+        return;
+    }
+
+    for (int j = 0; j < i / 2; j++) {
+        char temp = buffer[j];
+        buffer[j] = buffer[i - j - 1];
+        buffer[i - j - 1] = temp;
+    }
+
+    buffer[i] = '\0';
+}
 
 static bool print(const char* data, size_t length) {
 	const unsigned char* bytes = (const unsigned char*) data;
@@ -80,6 +126,21 @@ int printf(const char* restrict format, ...) {
 			if (!print(str, len))
 				return -1;
 			written += len;
+		} else if(*format == 'x' || *format == 'X') {
+			format++;
+			int number = va_arg(parameters, int);
+			char str[256];
+
+			if(*format == 'x')
+				intToString(number, str, 'x');
+			else
+				intToString(number, str, 'X');
+
+			size_t len = strlen(str);
+			if(!print(str, len))
+				return -1;
+			written += strlen(str);
+
 		} else {
 			format = format_begun_at;
 			size_t len = strlen(format);