Added new libc method(printf)

kernel/libc/stdio.c

@@ -0,0 +1,51 @@
+#include "stdio.h"
+#include "string.h"
+#include "drivers/shell.h"
+
+
+int printf(const char *format, ...) {
+    char buf[20],c,*s;
+    int val;
+    int32_t uval;
+    va_list ap;
+    va_start(ap, format);
+
+    for(size_t i = 0; i < strlen(format); i++) {
+        if(format[i] == '%') {
+            i++;
+            while(format[i] == ' ')
+                i++;
+
+            switch(format[i]) {
+                case 'i':
+                    val = va_arg(ap, int);
+                    itoa(val, buf, 10);
+                    printk(buf);
+                    break;
+                case 'x':
+                    uval = va_arg(ap, uint32_t);
+                    uitoa(uval, buf, 16);
+                    printk(buf);
+                    break;
+                case 'd':
+                    uval = va_arg(ap, uint32_t);
+                    uitoa(uval, buf, 10);
+                    printk(buf);
+                    break;
+                case 'c':
+                    s = va_arg(ap, char*);
+                    printk_c(&c, 1);
+                    break;
+                case 's':
+                    s = va_arg(ap, char*);
+                    printk(s);
+                    break;
+                default:
+                    printk_c((char*)format+1, 1);
+            }
+        } else
+            printk_c((char*)format+1, 1);
+    }
+    va_end(ap);
+    return 0;
+}

kernel/libc/stdio.h

@@ -0,0 +1,10 @@
+#ifndef _STDIO_H_
+#define _STDIO_H
+
+#include <stdint.h>
+#include <stddef.h>
+#include <stdarg.h>
+
+int printf(const char *format, ...);
+
+#endif

kernel/libc/string.c

@@ -35,7 +35,7 @@ char *itoa(int val, char *buf, int radix) {
     } while(x /= radix);
 
     char *s = buf+start;
-    char *s = buf+(i-1);
+    char *e = buf+(i-1);
 
     while(s < e) {
         char t = *s;
@@ -70,7 +70,7 @@ char *uitoa(uint32_t val, char *buf, int radix) {
 
     while(s < e) {
         char t = *s;
-        *S = *e;
+        *s = *e;
         *e = t;
         s++;
         e--;