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+    /*
+
+    Copyright (C) 2000 Stefan Westerfeld
+                       stefan@space.twc.de
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Library General Public
+    License as published by the Free Software Foundation; either
+    version 2 of the License, or (at your option) any later version.
+  
+    This library 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
+    Library General Public License for more details.
+   
+    You should have received a copy of the GNU Library General Public License
+    along with this library; see the file COPYING.LIB.  If not, write to
+    the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+    Boston, MA 02111-1307, USA.
+
+    */
+
+#ifndef AUDIOSUBSYS_H
+#define AUDIOSUBSYS_H
+#include <string>
+
+#include "arts_export.h"
+#include "pipebuffer.h"
+#include "startupmanager.h"
+
+/*
+ * BC - Status (2002-03-08): AudioSubSystem, ASProducer, ASConsumer.
+ *
+ * These classes are kept binary compatible. You can rely on them.
+ * AudioSubSystem has a private data pointer to do so. Even if ports to
+ * other architectures or hardware will require different organization
+ * (i.e. no fragments, direct memory access via mmap), the data members
+ * and functions exported here MAY NOT BE CHANGED. Use the private data
+ * pointer for adding data members.
+ *
+ * If ASProducer/ASConsumer doesn't suit the needs any longer, do NOT
+ * change them. Add new classes instead.
+ */
+
+namespace Arts {
+
+class ASProducer {
+public:
+	virtual void needMore() = 0;
+};
+
+// FIXME: haveMore won't be called currently
+class ASConsumer {
+public:
+	virtual void haveMore() = 0;
+};
+
+class ARTS_EXPORT AudioSubSystemStart :public StartupClass {
+protected:
+	class AudioSubSystem *_instance;
+public:
+	inline AudioSubSystem *the() { return _instance; };
+	void startup();
+	void shutdown();
+};
+
+class AudioSubSystemPrivate;
+
+class ARTS_EXPORT AudioSubSystem {
+	class AudioSubSystemPrivate *d;
+
+	std::string _error;
+	char *fragment_buffer;
+
+	int _fragmentCount;
+	int _fragmentSize;
+
+	bool _running;
+	PipeBuffer wBuffer, rBuffer;
+	ASConsumer *consumer;
+	ASProducer *producer;
+
+	friend class AudioSubSystemStart;
+	AudioSubSystem();
+	~AudioSubSystem();
+
+	void close();
+	void initAudioIO();
+
+	/**
+	 * checks that full duplex doesn't go out of sync
+	 */
+	void adjustDuplexBuffers();
+
+	/**
+	 * creates count empty fragments of input in rBuffer if count > 0
+	 * removes count fragments of input from rBuffer if count < 0
+	 */
+	void adjustInputBuffer(int count);
+
+public:
+	enum { ioRead=1, ioWrite=2, ioExcept=4 };
+
+	// singleton
+	static AudioSubSystem *the();
+
+	/*
+	 * Currently, if you want to use the AudioSubSystem, you need to
+	 * 
+	 * 1. - attach one producer
+	 *    - attach one consumer (only for full duplex)
+	 *    - open the audio subsystem using open (watch the fd)
+	 *    (in any order)
+	 *
+	 * 2. react on the callbacks you get for the producer
+	 *
+	 * 3. if you don't need the audio subsystem any longer, call detach
+	 *    both, the producer and the cosumer.
+	 *
+	 * Be careful that you don't read/write from/to the audio subsystem
+	 * when running() is not true.
+	 */
+
+	bool attachProducer(ASProducer *producer);
+	bool attachConsumer(ASConsumer *consumer);
+
+	void detachProducer();
+	void detachConsumer();
+
+	/*
+	 * can be used to select the AudioIO class to use, reasonable choices
+	 * may be "oss" or "alsa" at this point in time - you need to choose
+	 * this before doing anything else
+	 */
+	void audioIO(const std::string& audioIO);
+	std::string audioIO();
+
+	// which device to use for audio output (default /dev/dsp)
+	void deviceName(const std::string& deviceName);
+	std::string deviceName();
+
+	void fragmentSize(int size);
+	int fragmentSize();
+
+	void fragmentCount(int fragments);
+	int fragmentCount();
+
+	void samplingRate(int samplingrate);
+	int samplingRate();
+
+	void channels(int channels);
+	int channels();
+
+	void format(int format);
+	int format();
+
+	/**
+	 * As opposed to format(), this one returns the number of bits used per
+	 * sample. Thats sometimes a difference, for instance 16bit big endian
+	 * encoding has the format() 17, whereas bits() would return 16.
+	 */
+	int bits();
+
+	void fullDuplex(bool newFullDuplex);
+	bool fullDuplex();
+
+	bool check();
+
+	/**
+	 * Opens the audio device.
+	 *
+	 * After opening, you must check selectReadFD() and selectWriteFD() to
+	 * select() on the appropriate file descriptors. Whenever select()ing is
+	 * successful, handleIO needs to be called.
+	 *
+	 * The type for handleIO must be set to ioRead if fd is ready for
+	 * reading, ioWrite if fd is ready for writing, ioExcept if something
+	 * special happend or any combination of these using bitwise or.
+	 *
+	 * @returns true if audio device has been opened successfully,
+	 *          false otherwise
+	 */
+	bool open();
+
+	/**
+	 * human readable error message that descibes why opening the audio device
+	 * failed
+	 */
+	const char *error();
+
+	/**
+	 * File descriptor to select on for reading (@see open()), -1 if there is
+	 * none.
+	 */
+	int selectReadFD();
+
+	/**
+	 * File descriptor to select on for writing (@see open()), -1 if there is
+	 * none.
+	 */
+	int selectWriteFD();
+
+	/**
+	 * Needs to be called to handle I/O on the filedescriptors given by
+	 * selectReadFD() and selectWriteFD() (@see open()).
+	 */
+	void handleIO(int type);
+
+	void read(void *buffer, int size);
+	void write(void *buffer, int size);
+
+	/**
+	 * this returns the time in seconds it will take until everything written
+	 * to the AudioSubSystem so far will be played - in other words, it returns
+	 * the time it will take until the next sample written by the application
+	 * will be heard by the user
+	 */
+	float outputDelay();
+
+	/**
+	 * returns true as long as the audio subsystem is opened and active (that
+	 * is, between successful opening, with attaching producer, and the first
+	 * detachConsumer/detachProducer)
+	 */
+	bool running();
+
+	/**
+	 * called during crashes, to release the opened device (and other resources)
+	 * don't use this method for other purposes than emergencies
+	 */
+	void emergencyCleanup();
+};
+
+}
+
+#endif /* AUDIOSUBSYS_H */