New adlib interface allowing for different emulation backends

Imported-from: https://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@3299

src/hardware/adlib.h

@@ -0,0 +1,121 @@
+#ifndef DOSBOX_ADLIB_H
+#define DOSBOX_ADLIB_H
+
+#include "dosbox.h"
+#include "mixer.h"
+#include "pic.h"
+
+namespace Adlib {
+
+struct Timer {
+	double start;
+	double delay;
+	bool enabled, overflow, masked;
+	Bit8u counter;
+	Timer() {
+		masked = false;
+		overflow = false;
+		enabled = false;
+		counter = 0;
+		delay = 0;
+	}
+	//Call update before making any further changes
+	void Update( double time ) {
+		if ( !enabled || !delay ) 
+			return;
+		double deltaStart = time - start;
+		//Only set the overflow flag when not masked
+		if ( deltaStart >= 0 && !masked ) {
+			overflow = 1;
+		}
+	}
+	//On a reset make sure the start is in sync with the next cycle
+	void Reset(const double& time ) {
+		overflow = false;
+		if ( !delay || !enabled )
+			return;
+		double delta = (time - start);
+		double rem = fmod( delta, delay );
+		double next = delay - rem;
+		start = time + next;		
+	}
+	void Stop( ) {
+		enabled = false;
+	}
+	void Start( const double& time, Bits scale ) {
+		//Don't enable again
+		if ( enabled ) {
+			return;
+		}
+		enabled = true;
+		delay = 0.001 * (256 - counter ) * scale;
+		start = time + delay;
+	}
+
+};
+
+struct Chip {
+	//Last selected register
+	Timer timer[2];
+	//Check for it being a write to the timer
+	bool Write( Bit32u addr, Bit8u val );
+	//Read the current timer state, will use current double
+	Bit8u Read( );
+};
+
+//The type of handler this is
+typedef enum {
+	MODE_OPL2,
+	MODE_DUALOPL2,
+	MODE_OPL3,
+} Mode;
+
+class Handler {
+public:
+	//Write an address to a chip, returns the address the chip sets
+	virtual Bit32u WriteAddr( Bit32u port, Bit8u val ) = 0;
+	//Write to a specific register in the chip
+	virtual void WriteReg( Bit32u addr, Bit8u val ) = 0;
+	//Generate a certain amount of samples
+	virtual void Generate( MixerChannel* chan, Bitu samples ) = 0;
+	//Initialize at a specific sample rate and mode
+	virtual void Init( Bitu rate ) = 0;
+};
+
+//The cache for 2 chips or an opl3
+typedef Bit8u RegisterCache[512];
+
+//Internal class used for dro capturing
+class Capture;
+
+class Module {
+	//Mode we're running in
+	Mode mode;
+	//Last selected address in the chip for the different modes
+	union {
+		Bit32u normal;
+		Bit8u dual[2];
+	} reg;
+	void CacheWrite( Bit32u reg, Bit8u val );
+	void DualWrite( Bit8u index, Bit8u reg, Bit8u val );
+public:
+	MixerChannel* chan;
+	Bit32u lastUsed;				//Ticks when adlib was last used to turn of mixing after a few second
+
+	Handler* handler;				//Handler that will generate the sound
+	RegisterCache cache;
+	Capture* capture;
+	Chip	chip[2];
+
+	//Handle port writes
+	void PortWrite( Bitu port, Bitu val, Bitu iolen );
+	Bitu PortRead( Bitu port, Bitu iolen );
+	void Init( Mode m );
+
+	Module();
+};
+
+
+};		//Adlib namespace
+
+#endif