implement printf like function

core/main.c

@@ -22,7 +22,7 @@ void kmain(unsigned long magic, unsigned long addr)
 {
     unsigned long upper_mem = 0;
     initVGA(BLACK, GREEN);
-    printString("Setting up IDT\n");
+    printf("Setting up IDT\n");
     gdtSetup();
     idtSetup();
     irqSetup();
@@ -32,39 +32,31 @@ void kmain(unsigned long magic, unsigned long addr)
         multiboot_info_t *mbi = (multiboot_info_t *)addr;
         /* Are mem_* valid? */
         if (CHECK_FLAG(mbi->flags, 0)){
-            printString("mem_lower = ");
-            printInt((unsigned)mbi->mem_lower);
-            printString("KB mem_upper = ");
-            printInt((unsigned)mbi->mem_upper);
-            printString("KB\n");
+            printf("mem_lower = %dKB mem_upper %dKB\n", mbi->mem_lower, mbi->mem_upper);
             upper_mem = mbi->mem_upper;
         }
 
         /* Is boot_device valid? */
         if (CHECK_FLAG(mbi->flags, 1)){
-            printString("boot_device = ");
-            printInt((unsigned)mbi->boot_device);
-            printString("\n");
+            printf("boot_device = %d\n", mbi->boot_device);
         }
 
         /* Is the command line passed? */
         if (CHECK_FLAG(mbi->flags, 2)){
-            printString("cmdline = ");
-            printString((char *)mbi->cmdline);
-            printString("\n");
+            printf("cmdline = %s\n", (char *)mbi->cmdline);
         }
     }
 
     if(upper_mem == 0){
-        printString("Cannot get upper phy mem bound. Using default value 32MB\n");
+        printf("Cannot get upper phy mem bound. Using default value 32MB\n");
         upper_mem = 32 * 1024;
     }
     memInit(upper_mem);
 
-    printString("Setting up IRQ handlers\n");
+    printf("Setting up IRQ handlers\n");
     irqSetRoutine(IRQ_KEYBOARD, keyboard_handler);
     irqSetRoutine(IRQ_TIMER, timer_handler);
-    printString("Enabling HW interrupts\n");
+    printf("Enabling HW interrupts\n");
     exceptionSetRoutine(EXCEPTION_DOUBLE_FAULT, print_handler);
     // Enabling the HW interrupts
     asm volatile("sti\n");
@@ -72,5 +64,5 @@ void kmain(unsigned long magic, unsigned long addr)
     while (1) {
         printIntDetails(count++, GREEN, BLACK, 0, VGA_HEIGHT - 1);
     }
-    printString("exiting\n");
+    printf("exiting\n");
 }

core/mem.c

@@ -5,11 +5,7 @@ struct mem_desc *page_desc = (struct mem_desc *)&__ld_kernel_end;
 
 int memInit(unsigned long upper_mem)
 {
-	printString("Free Mem going from ");
-	printInt((unsigned long)&__ld_kernel_end);
-	printString(" to ");
-	printInt(upper_mem * 1024);
-	printString("\n");
+	printf("Free Mem going from %d to %d\n", &__ld_kernel_end, upper_mem *1024);
 	unsigned long memdesc_end =
 	    (unsigned long)page_desc +
 	    ((upper_mem) / (PAGE_SIZE / 1024)) * sizeof(struct mem_desc);

drivers/keyboard.c

@@ -280,9 +280,9 @@ void keyboard_do_irq()
 						break;
 					default:
 						if (lshift || rshift)
-							printString(scancode_shift[(int)c]);
+							printf(scancode_shift[(int)c]);
 						else
-							printString(scancode[(int)c]);
+							printf(scancode[(int)c]);
 				}
 			}else {
 				c = c - BREAK_CODE;

drivers/vga.c

@@ -85,6 +85,53 @@ void vgaScrollUp(void)
 	}
 }
 
+void vprintf(const char *format, va_list ap)
+{
+	int i = 0;
+	while (format[i] != '\0') {
+		switch (format[i]) {
+			case '%':
+				switch (format[i + 1]) {
+					case 'i':
+					case 'd': {
+						int d = va_arg(ap, int);
+						printInt(d);
+						break;
+					}
+					case 'c': {
+						int c = va_arg(ap, int);
+						printChar((char)c);
+						break;
+					}
+					case 's': {
+						char *str = va_arg(ap, char *);
+						if(!str)
+							str = "[NULL STR]";
+						printString(str);
+						break;
+					}
+					case '%':
+						printChar('%');
+						break;
+				}
+				i++;
+				break;
+
+			default:
+				printChar(format[i]);
+		}
+		i++;
+	}
+}
+
+void printf(const char *format, ...){
+	va_list ap;
+	va_start(ap, format);
+	vprintf(format, ap);
+	va_end(ap);
+}
+
+
 void printString(const char *str)
 {
 	while (*str) {

drivers/vga.h

@@ -16,6 +16,8 @@
 #define VGA_WIDTH  80
 #define VGA_HEIGHT 25
 
+void vprintf(const char *format, va_list ap);
+void printf(const char *format, ...);
 int initVGA(uint bgColor, uint color);
 void clearScreen(uint bgColor);
 void printInt(int integer);