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+/*
+  This file is part of Ingen.
+  Copyright 2007-2017 David Robillard <http://drobilla.net/>
+
+  Ingen is free software: you can redistribute it and/or modify it under the
+  terms of the GNU Affero General Public License as published by the Free
+  Software Foundation, either version 3 of the License, or any later version.
+
+  Ingen 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 Affero General Public License for details.
+
+  You should have received a copy of the GNU Affero General Public License
+  along with Ingen.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef INGEN_ENGINEBASE_HPP
+#define INGEN_ENGINEBASE_HPP
+
+#include <chrono>
+#include <cstddef>
+#include <cstdint>
+
+#include "ingen/ingen.h"
+#include "ingen/types.hpp"
+
+namespace ingen {
+
+class Interface;
+
+/**
+   The audio engine which executes the graph.
+
+   @ingroup Ingen
+*/
+class INGEN_API EngineBase
+{
+public:
+	virtual ~EngineBase() = default;
+
+	/**
+	   Initialise the engine for local use (e.g. without a Jack driver).
+	   @param sample_rate Audio sampling rate in Hz.
+	   @param block_length Audio block length (i.e. buffer size) in frames.
+	   @param seq_size Sequence buffer size in bytes.
+	*/
+	virtual void init(double   sample_rate,
+	                  uint32_t block_length,
+	                  size_t   seq_size) = 0;
+
+	/**
+	   Return true iff the engine and driver supports dynamic ports.
+
+	   This returns false in situations where top level ports can not be
+	   created once the driver is running, which is the case for most
+	   environments outside Jack.
+	*/
+	virtual bool supports_dynamic_ports() const = 0;
+
+	/**
+	   Activate the engine.
+	*/
+	virtual bool activate() = 0;
+
+	/**
+	   Deactivate the engine.
+	*/
+	virtual void deactivate() = 0;
+
+	/**
+	   Begin listening on network sockets.
+	*/
+	virtual void listen() = 0;
+
+	/**
+	   Return true iff events are waiting to be processed.
+	*/
+	virtual bool pending_events() const = 0;
+
+	/**
+	   Flush any pending events.
+
+	   This function is only safe to call in sequential contexts, and runs both
+	   process thread and main iterations in lock-step.
+
+	   @param sleep_ms Interval in milliseconds to sleep between each block.
+	*/
+	virtual void flush_events(const std::chrono::milliseconds& sleep_ms) = 0;
+
+	/**
+	   Advance audio time by the given number of frames.
+	*/
+	virtual void advance(uint32_t nframes) = 0;
+
+	/**
+	   Locate to a given audio position.
+	*/
+	virtual void locate(uint32_t start, uint32_t sample_count) = 0;
+
+	/**
+	   Process audio for `sample_count` frames.
+
+	   If the return value is non-zero, events have been processed and are
+	   awaiting to be finalised (including responding and announcing any changes
+	   to clients) via a call to main_iteration().
+
+	   @return The number of events processed.
+	*/
+	virtual unsigned run(uint32_t sample_count) = 0;
+
+	/**
+	   Indicate that a quit is desired.
+
+	   This function simply sets a flag which affects the return value of
+	   main_iteration, it does not actually force the engine to stop running or
+	   block.  The code driving the engine is responsible for stopping and
+	   cleaning up when main_iteration returns false.
+	*/
+	virtual void quit() = 0;
+
+	/**
+	   Run a single iteration of the main context.
+
+	   The main context post-processes events and performs housekeeping duties
+	   like collecting garbage.  This should be called regularly, e.g. a few
+	   times per second.  The return value indicates whether execution should
+	   continue; i.e. if false is returned, a quit has been requested and the
+	   caller should cease calling main_iteration() and stop the engine.
+	*/
+	virtual bool main_iteration() = 0;
+
+	/**
+	   Register a client to receive updates about engine changes.
+	*/
+	virtual void register_client(SPtr<Interface> client) = 0;
+
+	/**
+	   Unregister a client.
+	*/
+	virtual bool unregister_client(SPtr<Interface> client) = 0;
+};
+
+} // namespace ingen
+
+#endif // INGEN_ENGINEBASE_HPP