diff --git a/Makefile b/Makefile
index fa75c0a0..52097446 100644
--- a/Makefile
+++ b/Makefile
@@ -72,6 +72,7 @@ LIB_SOURCES =	src/libhttp.c					\
 		src/httplib_handle_request.c			\
 		src/httplib_handle_websocket_request.c		\
 		src/httplib_initialize_ssl.c			\
+		src/httplib_is_not_modified.c			\
 		src/httplib_is_websocket_protocol.c		\
 		src/httplib_load_dll.c				\
 		src/httplib_lock_unlock_connection.c		\
diff --git a/src/httplib_is_not_modified.c b/src/httplib_is_not_modified.c
new file mode 100644
index 00000000..b8ecbb9d
--- /dev/null
+++ b/src/httplib_is_not_modified.c
@@ -0,0 +1,53 @@
+/* 
+ * Copyright (c) 2016 Lammert Bies
+ * Copyright (c) 2013-2016 the Civetweb developers
+ * Copyright (c) 2004-2013 Sergey Lyubka
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+
+
+#include "libhttp-private.h"
+
+
+
+/*
+ * int XX_httplib_is_not_modified( const struct mg_connection *conn, const struct file *filep );
+ *
+ * The function XX_httplib_is_not_modified() returns true, if a resource has
+ * not been modified sinze a given datetime and a 304 response should therefore
+ * be sufficient.
+ */
+
+#if !defined(NO_CACHING)
+
+int XX_httplib_is_not_modified( const struct mg_connection *conn, const struct file *filep ) {
+
+	char etag[64];
+	const char *ims = mg_get_header( conn, "If-Modified-Since" );
+	const char *inm = mg_get_header( conn, "If-None-Match"     );
+
+	XX_httplib_construct_etag( etag, sizeof(etag), filep );
+	if ( filep == NULL ) return 0;
+	return (inm != NULL && !mg_strcasecmp(etag, inm)) || (ims != NULL && (filep->last_modified <= XX_httplib_parse_date_string(ims)));
+
+}  /* XX_httplib_is_not_modified */
+
+#endif /* !NO_CACHING */
diff --git a/src/libhttp-private.h b/src/libhttp-private.h
index b96fe628..2b727b1f 100644
--- a/src/libhttp-private.h
+++ b/src/libhttp-private.h
@@ -888,6 +888,7 @@ void			XX_httplib_close_all_listening_sockets( struct mg_context *ctx );
 void			XX_httplib_close_connection( struct mg_connection *conn );
 void			XX_httplib_close_socket_gracefully( struct mg_connection *conn );
 int			XX_httplib_connect_socket( struct mg_context *ctx, const char *host, int port, int use_ssl, char *ebuf, size_t ebuf_len, SOCKET *sock, union usa *sa );
+void			XX_httplib_construct_etag( char *buf, size_t buf_len, const struct file *filep );
 int			XX_httplib_consume_socket( struct mg_context *ctx, struct socket *sp, int thread_index );
 void			XX_httplib_delete_file( struct mg_connection *conn, const char *path );
 void			XX_httplib_discard_unread_request_data( struct mg_connection *conn );
@@ -933,6 +934,7 @@ int			XX_httplib_match_prefix(const char *pattern, size_t pattern_len, const cha
 void			XX_httplib_mkcol( struct mg_connection *conn, const char *path );
 int			XX_httplib_must_hide_file( struct mg_connection *conn, const char *path );
 const char *		XX_httplib_next_option( const char *list, struct vec *val, struct vec *eq_val );
+time_t			XX_httplib_parse_date_string( const char *datetime );
 int			XX_httplib_parse_http_headers( char **buf, struct mg_request_info *ri );
 int			XX_httplib_parse_http_message( char *buf, int len, struct mg_request_info *ri );
 int			XX_httplib_parse_net( const char *spec, uint32_t *net, uint32_t *mask );
diff --git a/src/libhttp.c b/src/libhttp.c
index ad85c7dc..86840cba 100644
--- a/src/libhttp.c
+++ b/src/libhttp.c
@@ -3565,7 +3565,7 @@ static int get_month_index(const char *s) {
 
 
 /* Parse UTC date-time string, and return the corresponding time_t value. */
-static time_t parse_date_string(const char *datetime) {
+time_t XX_httplib_parse_date_string( const char *datetime ) {
 
 	char month_str[32] = {0};
 	int second;
@@ -3596,7 +3596,9 @@ static time_t parse_date_string(const char *datetime) {
 	}
 
 	return result;
-}
+
+}  /* XX_httplib_parse_date_string */
+
 #endif /* !NO_CACHING */
 
 
@@ -4874,12 +4876,13 @@ int XX_httplib_parse_range_header( const char *header, int64_t *a, int64_t *b )
 }  /* XX_httplib_parse_range_header */
 
 
-static void construct_etag(char *buf, size_t buf_len, const struct file *filep) {
+void XX_httplib_construct_etag( char *buf, size_t buf_len, const struct file *filep ) {
 
 	if (filep != NULL && buf != NULL) {
 		XX_httplib_snprintf(NULL, NULL, buf, buf_len, "\"%lx.%" INT64_FMT "\"", (unsigned long)filep->last_modified, filep->size);
 	}
-}
+
+}  /* XX_httplib_construct_etag */
 
 
 void XX_httplib_fclose_on_exec( struct file *filep, struct mg_connection *conn ) {
@@ -4997,7 +5000,7 @@ void XX_httplib_handle_static_file_request( struct mg_connection *conn, const ch
 	 * http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.3 */
 	XX_httplib_gmt_time_string(date, sizeof(date), &curtime);
 	XX_httplib_gmt_time_string(lm, sizeof(lm), &filep->last_modified);
-	construct_etag(etag, sizeof(etag), filep);
+	XX_httplib_construct_etag(etag, sizeof(etag), filep);
 
 	mg_printf(conn, "HTTP/1.1 %d %s\r\n" "%s%s%s" "Date: %s\r\n", conn->status_code, msg, cors1, cors2, cors3, date);
 	XX_httplib_send_static_cache_header(conn);
@@ -5046,7 +5049,7 @@ void XX_httplib_handle_not_modified_static_file_request( struct mg_connection *c
 	conn->status_code = 304;
 	XX_httplib_gmt_time_string(date, sizeof(date), &curtime);
 	XX_httplib_gmt_time_string(lm, sizeof(lm), &filep->last_modified);
-	construct_etag(etag, sizeof(etag), filep);
+	XX_httplib_construct_etag(etag, sizeof(etag), filep);
 
 	mg_printf(conn, "HTTP/1.1 %d %s\r\n" "Date: %s\r\n", conn->status_code, mg_get_response_code_text(conn, conn->status_code), date);
 	XX_httplib_send_static_cache_header(conn);
@@ -5422,20 +5425,3 @@ int XX_httplib_substitute_index_file( struct mg_connection *conn, char *path, si
 
 }  /* XX_httplib_substitute_index_file */
 #endif
-
-
-#if !defined(NO_CACHING)
-/* Return True if we should reply 304 Not Modified. */
-int XX_httplib_is_not_modified( const struct mg_connection *conn, const struct file *filep ) {
-
-	char etag[64];
-	const char *ims = mg_get_header( conn, "If-Modified-Since" );
-	const char *inm = mg_get_header( conn, "If-None-Match"     );
-
-	construct_etag(etag, sizeof(etag), filep);
-	if ( filep == NULL ) return 0;
-	return (inm != NULL && !mg_strcasecmp(etag, inm)) || (ims != NULL && (filep->last_modified <= parse_date_string(ims)));
-
-}  /* XX_httplib_is_not_modified */
-
-#endif /* !NO_CACHING */