Index: src/string.c
==================================================================
--- src/string.c
+++ src/string.c
@@ -36,23 +36,32 @@
 struct CFWString {
 	CFWObject obj;
 	char *data;
 	size_t len;
 };
+
+size_t
+cfw_strnlen(const char *s, size_t max)
+{
+	size_t i = 0;
+
+	for (i = 0; i < max && *s != '\0'; s++)
+		i++;
+
+	return i;
+}
 
 char*
 cfw_strdup(const char *s)
 {
 	char *copy;
 	size_t len;
 
 	len = strlen(s);
 
-	if ((copy = malloc(len + 1)) == NULL) {
-		errno = ENOMEM;
+	if ((copy = malloc(len + 1)) == NULL)
 		return NULL;
-	}
 
 	memcpy(copy, s, len);
 	copy[len] = 0;
 
 	return copy;
@@ -62,19 +71,14 @@
 cfw_strndup(const char *s, size_t max)
 {
 	char *copy;
 	size_t len;
 
-	len = strlen(s);
-
-	if (len > max)
-		len = max;
-
-	if ((copy = malloc(len + 1)) == NULL) {
-		errno = ENOMEM;
-		return NULL;
-	}
+	len = cfw_strnlen(s, max);
+
+	if ((copy = malloc(len + 1)) == NULL)
+		return NULL;
 
 	memcpy(copy, s, len);
 	copy[len] = 0;
 
 	return copy;

Index: src/string.h
==================================================================
--- src/string.h
+++ src/string.h
@@ -30,10 +30,11 @@
 #include "class.h"
 #include "range.h"
 
 typedef struct CFWString CFWString;
 extern CFWClass *cfw_string;
+extern size_t cfw_strnlen(const char*, size_t);
 extern char* cfw_strdup(const char*);
 extern char* cfw_strndup(const char*, size_t);
 extern const char* cfw_string_c(CFWString*);
 extern size_t cfw_string_length(CFWString*);
 extern bool cfw_string_set(CFWString*, const char*);