string: implement strncmp()

libc/string.cc

@@ -57,3 +57,16 @@ char* strdup(const char *s)
     auto p = static_cast<char*>(malloc(strlen(s)+1));
     return strcpy(p, s);
 }
+
+int strncmp(const char *s1, const char *s2, size_t n)
+{
+    while (n && *s1 && *s2 && tolower(*s1) == tolower(*s2)) {
+        ++s1;
+        ++s2;
+        --n;
+    }
+    if (n == 0) {
+        return 0;
+    }
+    return int(tolower(*s2)) - int(tolower(*s1));
+}