diff --git a/src/string.cpp b/src/string.cpp
--- a/src/string.cpp
+++ b/src/string.cpp
@@ -185,18 +185,11 @@ void str_fix_scc_encoded(char *str, cons
 }
 
 
-/**
- * Scans the string for valid characters and if it finds invalid ones,
- * replaces them with a question mark '?' (if not ignored)
- * @param str the string to validate
- * @param last the last valid character of str
- * @param settings the settings for the string validation.
- */
-void str_validate(char *str, const char *last, StringValidationSettings settings)
+template <class T>
+static void str_validate(T &dst, const char *str, const char *last, StringValidationSettings settings)
 {
 	/* Assume the ABSOLUTE WORST to be in str as it comes from the outside. */
 
-	char *dst = str;
 	while (str <= last && *str != '\0') {
 		size_t len = Utf8EncodedCharLen(*str);
 		/* If the character is unknown, i.e. encoded length is 0
@@ -220,7 +213,7 @@ void str_validate(char *str, const char 
 			do {
 				*dst++ = *str++;
 			} while (--len != 0);
-		} else if ((settings & SVS_ALLOW_NEWLINE) != 0  && c == '\n') {
+		} else if ((settings & SVS_ALLOW_NEWLINE) != 0 && c == '\n') {
 			*dst++ = *str++;
 		} else {
 			if ((settings & SVS_ALLOW_NEWLINE) != 0 && c == '\r' && str[1] == '\n') {
@@ -232,12 +225,42 @@ void str_validate(char *str, const char 
 			if ((settings & SVS_REPLACE_WITH_QUESTION_MARK) != 0) *dst++ = '?';
 		}
 	}
+}
 
+/**
+ * Scans the string for valid characters and if it finds invalid ones,
+ * replaces them with a question mark '?' (if not ignored)
+ * @param str the string to validate
+ * @param last the last valid character of str
+ * @param settings the settings for the string validation.
+ */
+void str_validate(char *str, const char *last, StringValidationSettings settings)
+{
+	char *dst = str;
+	str_validate(dst, str, last, settings);
 	*dst = '\0';
 }
 
 /**
  * Scans the string for valid characters and if it finds invalid ones,
+ * replaces them with a question mark '?' (if not ignored)
+ * @param str the string to validate
+ * @param settings the settings for the string validation.
+ */
+std::string str_validate(const std::string &str, StringValidationSettings settings)
+{
+	auto buf = str.data();
+	auto last = buf + str.size();
+
+	std::ostringstream dst;
+	std::ostreambuf_iterator<char> dst_iter(dst);
+	str_validate(dst_iter, buf, last, settings);
+
+	return dst.str();
+}
+
+/**
+ * Scans the string for valid characters and if it finds invalid ones,
  * replaces them with a question mark '?'.
  * @param str the string to validate
  */