diff --git a/src/util/cstr_helper.c b/src/util/cstr_helper.c
index 9266551..2e33d50 100644
--- a/src/util/cstr_helper.c
+++ b/src/util/cstr_helper.c
@@ -2,21 +2,33 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include "cstr_helper.h"
 
-int copy_cstr(const char *source, char **destination, size_t *size)
+
+int copy_cstr(const char *source, char **dest)
 // Determines length, allocates memory, and returns a null terminated copy
 // Be Aware: caller is responsible for freeing memory
 {
     size_t len;
 
     len = strlen(source);
-    *destination = (char *) calloc(len + 1, sizeof(char));
+    *dest = (char *) calloc((len + 1), sizeof(char));
 
-    if (*destination == NULL)
+    if (*dest == NULL)
         return -1;
     else {
-        strncpy(*destination, source, len);
-        *size = len + 1;
+        strncpy(*dest, source, (len + 1));
+		strncat(*dest, "\0", 1);
     }
     return 0;
 }
+
+
+bool isnullterm_cstr(const char *source)
+{
+	if (strchr(source, '\0'))
+		return true;
+	else
+		return false;
+
+}
diff --git a/src/util/cstr_helper.h b/src/util/cstr_helper.h
index 1b435c1..55f71d0 100644
--- a/src/util/cstr_helper.h
+++ b/src/util/cstr_helper.h
@@ -3,7 +3,11 @@
 #define CSTR_HELPER_H_
 
 
-int copy_cstr(const char *source, char **destination, size_t *size);
+#include <stdbool.h>
+
+
+int copy_cstr(const char *source, char **destination);
+bool isnullterm_cstr(const char *source);
 
 
 #endif /* CSTR_HELPER_H_ */
diff --git a/src/util/filemanager.c b/src/util/filemanager.c
index 98d775c..49ca4a3 100644
--- a/src/util/filemanager.c
+++ b/src/util/filemanager.c
@@ -27,15 +27,14 @@
 
 
 typedef struct file_s {
-    char *filename;
-    size_t size;
+    char *filename;    // Assumes this is a null terminated string
     FILE *file;
 } file_handle_t;
 
 
 // local (private) functions
 int _fopen(FILE **f, const char *name, const char *mode);
-int _get_temp_filename(char **tempname, size_t *size);
+int _get_temp_filename(char **tempname);
 
 
 file_handle_t *create_file_manager() {
@@ -44,14 +43,13 @@ file_handle_t *create_file_manager() {
     file_handle = (file_handle_t *)calloc(1, sizeof(file_handle_t));
 
 	file_handle->filename = NULL;
-	file_handle->size = 0;
 	file_handle->file = NULL;
 
     return file_handle;
 }
 
 void delete_file_manager(file_handle_t *file_handle) {
-	
+
 	if (file_handle->file != NULL)
 		close_file(file_handle);
 
@@ -65,7 +63,7 @@ void get_filename(file_handle_t *file_handle, char **filename, size_t *size)
 // BE AWARE: The memory allocated here must be freed by the caller
 //
 {
-    copy_cstr(file_handle->filename, filename, size);
+    copy_cstr(file_handle->filename, filename);
 }
 
 
@@ -73,9 +71,9 @@ int open_file(file_handle_t *file_handle, const char *filename, const char *file
     int error = 0;
 
     if (filename == NULL)
-        _get_temp_filename(&(file_handle->filename), &(file_handle->size));
+        _get_temp_filename(&(file_handle->filename));
     else
-        copy_cstr(filename, &(file_handle->filename), &(file_handle->size));
+        copy_cstr(filename, &(file_handle->filename));
 
     if (file_mode == NULL)
         error = -1;
@@ -173,7 +171,7 @@ int _fopen(FILE **f, const char *name, const char *mode)
     return ret;
 }
 
-int _get_temp_filename(char **tempname, size_t *size)
+int _get_temp_filename(char **tempname)
 {
     int error = 0;
 
@@ -187,7 +185,7 @@ int _get_temp_filename(char **tempname, size_t *size)
         return error;
     }
     else
-        copy_cstr(name, tempname, size);
+        copy_cstr(name, tempname);
 
     // --- free the pointer returned by _tempnam
     if (name)
@@ -201,3 +199,12 @@ int _get_temp_filename(char **tempname, size_t *size)
 #endif
     return error;
 }
+
+bool is_valid(file_handle_t *file_handle)
+{
+	if ((file_handle->filename == NULL && file_handle->file == NULL) ||
+		(isnullterm_cstr(file_handle->filename) && file_handle != NULL))
+		return true;
+	else
+		return false;
+}
diff --git a/src/util/filemanager.h b/src/util/filemanager.h
index f0b00d2..93ee8d9 100644
--- a/src/util/filemanager.h
+++ b/src/util/filemanager.h
@@ -71,6 +71,9 @@ int close_file(file_handle_t *file_handle);
 int remove_file(file_handle_t *file_handle);
 
 
+bool is_valid(file_handle_t *file_handle);
+
+
 #if defined(__cplusplus)
 }
 #endif
diff --git a/tests/util/test_filemanager.cpp b/tests/util/test_filemanager.cpp
index 310c620..70ff6c6 100644
--- a/tests/util/test_filemanager.cpp
+++ b/tests/util/test_filemanager.cpp
@@ -40,6 +40,7 @@ BOOST_AUTO_TEST_CASE (test_create_destroy)
 
     file_handle = create_file_manager();
     BOOST_CHECK(file_handle != NULL);
+	BOOST_CHECK(is_valid(file_handle) == true);
 
     delete_file_manager(file_handle);
 }
@@ -54,6 +55,7 @@ BOOST_AUTO_TEST_CASE(test_open_close)
 
     error = open_file(file_handle, DATA_PATH_OUTPUT, "rb");
     BOOST_REQUIRE(error == 0);
+	BOOST_CHECK(is_valid(file_handle) == true);
 
     error = close_file(file_handle);
     BOOST_REQUIRE(error == 0);
@@ -85,7 +87,7 @@ BOOST_FIXTURE_TEST_CASE(test_temp_file, Fixture)
     printf_file(file_handle, "%s", "This is a test.");
 
     get_filename(file_handle, &filename, &size);
-    //BOOST_CHECK(check_string(filename, "./test_file.txt"));
+	BOOST_CHECK(is_valid(file_handle) == true);
 
     BOOST_CHECK(boost::filesystem::exists(filename) == true);