Implement LV2 worker extension.

This is done by way of a generic Worker object/thread, which currently just
applies to one LV2 plugin, but the idea is to share one thread and set of
buffers among many plugins.  The same pattern may also be useful elsewhere in
Ardour.  The responding part gets a bit tricker when sharing a worker between
plugins, it's not a blocker, and I'm lazy, sooo here's this.

This commit also adds a new portable in-process semaphore to PBD.  The existing
one is pretty weird and uses a named semaphore on OSX for reasons unknown to
me.  Perhaps as a quick fix to avoid POSIX semaphores being utterly broken on
OSX?  It would probably be a good idea to replace that with this new one, which
uses Mach kernel semaphores on OSX which work well, though I am not sure how
pedantically real-time safe they are to signal.


git-svn-id: svn://localhost/ardour2/branches/3.0@11790 d708f5d6-7413-0410-9779-e7cbd77b26cf

1 files changed, 90 insertions, 0 deletions

diff --git a/libs/ardour/ardour/worker.h b/libs/ardour/ardour/worker.h
new file mode 100644
index 0000000000..eca5aa21ca
--- /dev/null
+++ b/libs/ardour/ardour/worker.h
@@ -0,0 +1,90 @@
+/*
+  Copyright (C) 2012 Paul Davis
+  Author: David Robillard
+
+  This program is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 of the License, or
+  (at your option) any later version.
+
+  This program 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 General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program; if not, write to the Free Software
+  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#ifndef __ardour_worker_h__
+#define __ardour_worker_h__
+
+#include <stdint.h>
+
+#include <glibmm/thread.h>
+
+#include "pbd/ringbuffer.h"
+#include "pbd/semaphore.h"
+
+namespace ARDOUR {
+
+/**
+   An object that needs to schedule non-RT work in the audio thread.
+*/
+class Workee {
+public:
+	virtual ~Workee() {}
+
+	/**
+	   Do some work in the worker thread.
+	*/
+	virtual void work(uint32_t size, const void* data) = 0;
+
+	/**
+	   Handle a response from the worker thread in the audio thread.
+	*/
+	virtual void work_response(uint32_t size, const void* data) = 0;
+};
+
+/**
+   A worker thread for non-realtime tasks scheduled in the audio thread.
+*/
+class Worker
+{
+public:
+	Worker(Workee* workee, uint32_t ring_size);
+	~Worker();
+
+	/**
+	   Schedule work (audio thread).
+	   @return false on error.
+	*/
+	bool schedule(uint32_t size, const void* data);
+
+	/**
+	   Respond from work (worker thread).
+	   @return false on error.
+	*/
+	bool respond(uint32_t size, const void* data);
+
+	/**
+	   Emit any pending responses (audio thread).
+	*/
+	void emit_responses();
+
+private:
+	void run();
+
+	Workee*              _workee;
+	Glib::Thread*        _thread;
+	RingBuffer<uint8_t>* _requests;
+	RingBuffer<uint8_t>* _responses;
+	uint8_t*             _response;
+	PBD::Semaphore       _sem;
+	bool                 _exit;
+};
+
+} // namespace ARDOUR
+
+#endif  /* __ardour_worker_h__ */