add new realtime event loop abstraction which precise time keeping by using hrtimers on Linux, if they are available

git-svn-id: file:///home/lennart/svn/public/pulseaudio/branches/lennart@1689 fefdeb5f-60dc-0310-8127-8f9354f1896f

src/pulsecore/rtpoll.h

@@ -0,0 +1,71 @@
+#ifndef foopulsertpollhfoo
+#define foopulsertpollhfoo
+
+/* $Id$ */
+
+/***
+  This file is part of PulseAudio.
+
+  Copyright 2004-2006 Lennart Poettering
+
+  PulseAudio is free software; you can redistribute it and/or modify
+  it under the terms of the GNU Lesser General Public License as
+  published by the Free Software Foundation; either version 2.1 of the
+  License, or (at your option) any later version.
+
+  PulseAudio is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public
+  License along with PulseAudio; if not, write to the Free Software
+  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+  USA.
+***/
+
+#include <poll.h>
+#include <sys/types.h>
+
+#include <pulse/sample.h>
+
+/* An implementation of a "real-time" poll loop. Basically, this is
+ * yet another wrapper around poll(). However it has certain
+ * advantages over pa_mainloop and suchlike:
+ *
+ * 1) It uses timer_create() and POSIX real time signals to guarantee
+ * optimal high-resolution timing. Starting with Linux 2.6.21 hrtimers
+ * are available, and since right now only nanosleep() and the POSIX
+ * clock and timer interfaces have been ported to hrtimers (and not
+ * ppoll/pselect!) we have to combine ppoll() with timer_create(). The
+ * fact that POSIX timers and POSIX rt signals are used internally is
+ * completely hidden.
+ *
+ * 2) It allows raw access to the pollfd data to users
+ *
+ * 3) It allows arbitrary functions to be run before entering the
+ * actual poll() and after it.
+ *
+ * Only a single interval timer is supported..*/
+
+typedef struct pa_rtpoll pa_rtpoll;
+typedef struct pa_rtpoll_item pa_rtpoll_item;
+
+pa_rtpoll *pa_rtpoll_new(void);
+void pa_rtpoll_free(pa_rtpoll *p);
+
+void pa_rtpoll_install(pa_rtpoll *p);
+
+int pa_rtpoll_run(pa_rtpoll *f);
+void pa_rtpoll_set_itimer(pa_rtpoll *p, pa_usec_t usec);
+
+pa_rtpoll_item *pa_rtpoll_item_new(pa_rtpoll *p, unsigned n_fds);
+void pa_rtpoll_item_free(pa_rtpoll_item *i);
+
+struct pollfd *pa_rtpoll_item_get_pollfd(pa_rtpoll_item *i, unsigned *n_fds);
+
+void pa_rtpoll_item_set_before_callback(pa_rtpoll_item *i, int (*before_cb)(pa_rtpoll_item *i));
+void pa_rtpoll_item_set_after_callback(pa_rtpoll_item *i, void (*after_cb)(pa_rtpoll_item *i));
+void pa_rtpoll_item_set_userdata(pa_rtpoll_item *i, void *userdata);
+
+#endif