Added strlen and strcmp functions

Author: Retr0-code

OS.iso

@@ -42,4 +42,14 @@ extern uint16_t print_char(
 
 extern void clear(uint16_t* _tty_buf, color_t _c);
 
+/*	Calculates string length _s
+	returns length of string
+*/
+extern uint16_t strlen(const char* _s);
+
+/*	Compares string _s1 with string _s2
+	return true if _s1 = _s2
+*/
+extern bool strcmp(const char* _s1, const char* _s2);
+
 #endif

build/OS.bin

@@ -32,4 +32,30 @@ void clear(uint16_t* _tty_buf, color_t _c)
     for (uint8_t h = 0; h < VGA_HEIGHT; h++)
         for (uint8_t w = 0; w < VGA_WIDTH; w++)
             print_char(0x20, _c, h * VGA_WIDTH + w, _tty_buf);
+}
+
+uint16_t strlen(const char* _s)
+{
+    uint16_t len = 0;
+    while (_s[len] != 0x00)
+        len++ ;
+    return len;
+}
+
+bool strcmp(const char* _s1, const char* _s2)
+{
+    uint16_t s1_len = strlen(_s1);  // Length of first string
+    if (strlen(_s1) == strlen(_s2))
+    {
+        uint16_t i = 0;
+        while (_s1[i] == _s2[i])    // Char by char comparison
+            i++;
+        
+        if (i == s1_len) /*
+            If amount of iterations equals string length
+            means strings are equal
+        */
+            return true;
+    }
+    return false;
 }