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#pragma once

#include "clsDevice.h"

// Keyboard Device Emulation

//

// The keyboard controller code loops around until there are no more scan

// codes available from the keyboard. In real life an interrupt signal is

// generated by each scan code sent by the keyboard. There is no hardware

// buffering of scan-codes. In the emulation only a single emulation 

// interrupt is generated for a keypress(button) event and multiple scan

// codes are buffered. Rather than emulate the keyboard interface more

// closely the emulation is simplified and the driver software recognizes

// the way the emulation works. Otherwise it might be necessary to

// implement the keyboard interface in it's own thread with calls to

// Sleep() between each scan-code transmission.

// It should work because the interrupt routine checks for additional

// scan codes during it's processing. This is a case where the software

// for the system is designed around supporting the emulator.

// In real life there should never be two scan-codes sent by the keyboard

// close enough together for the loop in the keyboard code to be 

// effective. The loop is harmless enough as the scan-code status

// needs to be tested anyway. Whether its a while() or an if() is

// irrelevant.

class clsKeyboard : public clsDevice

{

        unsigned __int8 buffer[32];

        int head;

        int tail;

public:

        volatile unsigned __int8 scancode;

        volatile unsigned __int8 status;

        clsKeyboard(void);

        ~clsKeyboard(void);

        bool IsSelected(unsigned int ad) { return ((ad & 0xFFFFFFF0)==0xFFDC0000); };

        void Put(unsigned __int8 sc) {

                scancode = sc;

                buffer[head] = sc;

                head++;

                head &= 31;

        };

        unsigned __int8 Get() {

                unsigned __int8 sc;

                sc = 0;

                if (head != tail) {

                        sc = buffer[tail];

                        tail++;

                        tail &= 31;

                }

                return sc;

        };

        unsigned __int8 Peek(int amt) {

                unsigned __int8 sc;

                int ndx;

                ndx = tail + amt;

                ndx &= 31;

                sc = buffer[ndx];

                return sc;

        };

        unsigned __int8 GetStatus() {

                if (head != tail)

                        return 0x80;

                else

                        return 0x00;

        };

};