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audio/chip.h

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+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * 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 3 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, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef AUDIO_CHIP_H
+#define AUDIO_CHIP_H
+
+#include "common/func.h"
+#include "common/ptr.h"
+
+#include "audio/audiostream.h"
+
+namespace Audio {
+class SoundHandle;
+
+class Chip {
+public:
+	virtual ~Chip() {}
+
+	/**
+	 * The type of the timer callback functor.
+	 */
+	typedef Common::Functor0<void> TimerCallback;
+
+	/**
+	 * Start the sound chip with callbacks.
+	 */
+	void start(TimerCallback *callback, int timerFrequency);
+
+	/**
+	 * Stop the sound chip
+	 */
+	void stop();
+
+	/**
+	 * Change the callback frequency. This must only be called from a
+	 * timer proc.
+	 */
+	virtual void setCallbackFrequency(int timerFrequency) = 0;
+
+protected:
+	/**
+	 * Start the callbacks.
+	 */
+	virtual void startCallbacks(int timerFrequency) = 0;
+
+	/**
+	 * Stop the callbacks.
+	 */
+	virtual void stopCallbacks() = 0;
+
+	/**
+	 * The functor for callbacks.
+	 */
+	Common::ScopedPtr<TimerCallback> _callback;
+};
+
+/**
+ * A Chip that represents a real sound chip, as opposed to an emulated one.
+ *
+ * This will use an actual timer instead of using one calculated from
+ * the number of samples in an AudioStream::readBuffer call.
+ */
+class RealChip : virtual public Chip {
+public:
+	RealChip();
+	virtual ~RealChip();
+
+	// Chip API
+	void setCallbackFrequency(int timerFrequency);
+
+protected:
+	// Chip API
+	void startCallbacks(int timerFrequency);
+	void stopCallbacks();
+	virtual void onTimer();
+
+private:
+	static void timerProc(void *refCon);
+
+	uint _baseFreq;
+	uint _remainingTicks;
+
+	enum {
+		kMaxFreq = 100
+	};
+};
+
+/**
+ * A Chip that represents an emulated sound chip.
+ *
+ * This will send callbacks based on the number of samples
+ * decoded in readBuffer().
+ */
+class EmulatedChip : virtual public Chip, protected Audio::AudioStream {
+protected:
+	static const int FIXP_SHIFT = 16;
+
+public:
+	EmulatedChip();
+	virtual ~EmulatedChip();
+
+	// Chip API
+	void setCallbackFrequency(int timerFrequency) override;
+
+	// AudioStream API
+	int readBuffer(int16 *buffer, const int numSamples) override;
+	int getRate() const override;
+	bool endOfData() const override { return false; }
+
+protected:
+	// Chip API
+	void startCallbacks(int timerFrequency) override final;
+	void stopCallbacks() override final;
+
+	/**
+	 * Read up to 'length' samples.
+	 *
+	 * Data will be in native endianess, 16 bit per sample, signed.
+	 * For stereo chips, buffer will be filled with interleaved
+	 * left and right channel samples, starting with a left sample.
+	 * Furthermore, the samples in the left and right are summed up.
+	 * So if you request 4 samples from a stereo chip, you will get
+	 * a total of two left channel and two right channel samples.
+	 */
+	virtual void generateSamples(int16 *buffer, int numSamples) = 0;
+
+private:
+	int _baseFreq;
+
+	int _nextTick;
+	int _samplesPerTick;
+
+	Audio::SoundHandle *_handle;
+};
+
+} // End of namespace Audio
+
+#endif