AudioSource.h
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AudioSource.h
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	#ifndef _ECHOAUDIOSOURCE_H_
	#define _ECHOAUDIOSOURCE_H_
	#include <echo/Types.h>
	#include <echo/Chrono/Chrono.h>

	namespace Echo
	{
	class AudioBuffer;

	/**
	* Abstract Base class for Audio Sources
	*/
	class AudioSource
	{
	public:
	AudioSource();
	virtual ~AudioSource();

	/**
	* Restart the audio source.
	* Will be called when the AudioBuffer finds that it reached the end of the
	* source. After Reset is called. If the source is a audio file then Restart()
	* should start reading from the start of the file's audio data again.
	*/
	virtual void Restart()=0;

	/**
	* Get length of the buffer.
	* @return the length of the Source in seconds.
	*/
	virtual Seconds GetLength()=0;

	/**
	* Get the number of channels the audio source provides.
	* @return the number of channels, e.g. 1 for mono and 2 for stereo.
	*/
	virtual u32 GetNumChannels()=0;

	//////////////////////////////////////////////////////////////////////////
	//////////////////////////////////////////////////////////////////////////
	/**
	* UpdateBuffer is called by the buffer on the source when the buffer needs to be updated with more data.
	* The frequency is determined by the buffer and can be platform dependent. The buffer will call this
	* more rapidly when it is nearer to being played out in an attempt to be filled with enough data to play
	* without interruptions.
	* This method should call AudioBuffer::Append() to append up to numBytes to the buffer.
	* @param buffer the audio buffer to append data to.
	* @param numBytes the requested number of bytes to append to the buffer.
	* @return the number of bytes.
	*/
	virtual u32 UpdateBuffer(AudioBuffer& buffer, u32 numBytes)=0;

	/**
	* Get the bit depth of a sample.
	* @return the bit depth.
	*/
	virtual u32 GetBitsPerSample() = 0;

	/**
	* Get the number of bytes per sample
	* @return the number of bytes per sample.
	*/
	inline u32 GetBytesPerSample()
	{
	return GetBitsPerSample()/8;
	}

	/**
	* Get the sample rate.
	* This is samples per second,known as hertz.
	* @return the sample rate.
	*/
	virtual u32 GetSampleRate() = 0;

	/**
	* Helper method to convert the number of bytes to the number of samples.
	* @param bytes the number of bytes.
	* @return the number of samples the number of bytes would make up.
	*/
	inline Size ConvertBytesToSamples(Size bytes)
	{
	return (bytes / GetBytesPerSample());
	}

	/**
	* Helper method to convert the number of bytes to seconds.
	* @param bytes the number of bytes.
	* @return the time in seconds that the number of bytes would make up as audio data for
	* this buffer.
	*/
	inline Seconds ConvertBytesToSeconds(Size bytes)
	{
	return Seconds((ConvertBytesToSamples(bytes) / GetSampleRate()) / GetNumChannels());
	}

	/**
	* Helper method to convert the number of samples to the number of bytes.
	* @note Be sure the number of samples includes the total count for all channels for the
	* time you expect.
	* @param samples the number of samples.
	* @return the number of bytes the given number of samples would require.
	*/
	inline Size ConvertSamplesToBytes(Size samples)
	{
	return (samples * GetBytesPerSample());
	}

	/**
	* Helper method to convert the number of samples to seconds.
	* @param totalSampleCountForAllChannels the number of samples for all channels,
	* if the sample rate is 16000 and there are two channels then passing 16000 would
	* mean this method returns 0.5 seconds.
	* @return the time in seconds that the number of samples would make up if intended for
	* this buffer.
	*/
	inline Seconds ConvertSamplesToSeconds(Size totalSampleCountForAllChannels)
	{
	return Seconds((totalSampleCountForAllChannels / GetSampleRate()) / GetNumChannels());
	}

	/**
	* Helper method to convert the seconds to the required number of bytes.
	* This method returns the total number of bytes required for all channels to make
	* the specified seconds worth of audio.
	* @param seconds the number of seconds.
	* @return the number of bytes required for time in seconds of audio.
	*/
	inline Size ConvertSecondsToBytes(Seconds seconds)
	{
	return (ConvertSecondsToSamples(seconds) * GetBytesPerSample());
	}

	/**
	* Helper method to convert the seconds to the required number of samples.
	* This method returns the total number of samples required for all channels to make
	* the specified seconds worth of audio.
	* @param seconds the number of seconds.
	* @return the number of samples required for time in seconds of audio.
	*/
	inline Size ConvertSecondsToSamples(Seconds seconds)
	{
	return seconds.count() * GetSampleRate() * GetNumChannels();
	}
	};
	}
	#endif

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