add subject/observer interface

+#ifndef __OBSERVER_H__
+#define __OBSERVER_H__
+
+typedef void (* fptr_observerNotify)(void *, void*);
+
+extern const struct interface i_Observer;
+
+struct i_Observer {
+	const struct interface * const _;
+	fptr_observerNotify      notify;
+};
+
+extern void observerNotify(void *, void *);
+
+#endif // __OBSERVER_H__
+
+// vim: set ts=4 sw=4:

+#ifndef __SUBJECT_H__
+#define __SUBJECT_H__
+
+typedef void (* fptr_subjectAttach)(void *, void *);
+typedef void (* fptr_subjectDetach)(void *, void *);
+typedef void (* fptr_subjectNotify)(void *);
+
+extern const struct interface i_Subject;
+
+struct i_Subject {
+	const struct interface * const _;
+	fptr_subjectAttach       attach;
+	fptr_subjectDetach       detach;
+	fptr_subjectNotify       notify;
+};
+
+extern void subjectAttach(void *, void *);
+extern void subjectDetach(void *, void *);
+extern void subjectNotify(void *);
+
+#endif // __SUBJECT_H__
+
+// vim: set ts=4 sw=4:

@@ -2,7 +2,8 @@ ACLOCAL_AMFLAGS = -I m4
 AUTOMAKE_OPTIONS = subdir-objects
 
 IFACE  = interface/class.c interface/stream_reader.c interface/logger.c \
-	 interface/stream_writer.c interface/http_intro.c
+	 interface/stream_writer.c interface/http_intro.c \
+	 interface/subject.c interface/observer.c
 CLASS  = class.c interface.c
 SOCKET = socket.c socket/accept.c socket/connect.c socket/listen.c
 SERVER = server.c server/run.c server/close_conn.c

+#include "class.h"
+#include "interface/observer.h"
+
+const struct interface i_Observer = {
+	"observer",
+	1
+};
+
+void
+observerNotify(void * observer, void * subject)
+{
+	CALL(observer, Observer, notify, subject);
+}
+
+// vim: set ts=4 sw=4:

+#include "class.h"
+#include "interface/subject.h"
+
+const struct interface i_Subject = {
+	"subject",
+	3
+};
+
+void
+subjectAttach(void * subject, void * observer)
+{
+	CALL(subject, Subject, attach, observer);
+}
+
+void
+subjectDetach(void * subject, void * observer)
+{
+	CALL(subject, Subject, detach, observer);
+}
+
+void
+subjectNotify(void * subject)
+{
+	CALL(subject, Subject, notify);
+}
+
+// vim: set ts=4 sw=4: