Category : C++ Source Code
Archive   : C_ALL.ZIP
Filename : TI652.ASC

PRODUCT : C++ NUMBER : 652
VERSION : All
OS : PC DOS
DATE : September 3, 1992 PAGE : 1/1

TITLE : Interrupt Handlers as Member Functions





A static member function of a class can be used as an interrupt
handler. It is not possible to use a 'regular or normal' member
function as an Interrupt Handler because such functions expect a
hidden parameter when called ( i.e. the 'this' pointer ) and the
Intel interrupt mechanism cannot push the 'this' pointer prior to
calling a handler. ( See your C++ documentation for more
information about the 'this' parameter passed to member functions
).


The following provides an example where a static member function
is used as an interrupt handler. The class also contains a
pointer to an instance of the class, therefore providing more
flexibility to the handler. The only requirement is that the
static pointer must be initialized to a valid instance of the
class:


#include
#include
#include


_CLASSDEF( ISR )

class ISR
{
int intNumber;
void interrupt (*oldHandler)(...);

public:
static PISR curISR;

ISR( int );
~ISR();
static void interrupt __handler(...);
virtual void handler();

virtual void justBeep();
};
PISR ISR::curISR = NULL;














PRODUCT : C++ NUMBER : 652
VERSION : All
OS : PC DOS
DATE : September 3, 1992 PAGE : 2/1

TITLE : Interrupt Handlers as Member Functions




ISR::ISR( int iNum )
{
intNumber = iNum;
oldHandler = getvect( intNumber );
setvect( intNumber, (void interrupt(*)(...))__handler );
}


ISR::~ISR()
{
setvect( intNumber, (void interrupt (*)(...))oldHandler );
curISR = NULL;
}


void interrupt ISR::__handler(...)
{
if ( curISR )
curISR->handler();
}


void ISR::handler()
{
justBeep();
}


void ISR::justBeep()
{
_AX = 0x0E07;
geninterrupt( 0x10 );
}


int main( void )
{
int key = 0;
ISR myPrintISR( 5 );

ISR::curISR = &myPrintISR;

printf("Hit ESC to terminate or PrintScreen to trigger\n" );













PRODUCT : C++ NUMBER : 652
VERSION : All
OS : PC DOS
DATE : September 3, 1992 PAGE : 3/1

TITLE : Interrupt Handlers as Member Functions




printf("the Interrupt 5 and listen to my Beep !\n" );

while( key != 27 )
{
if ( !(key = getch()) )
key = getch();
putch( key );
}
return( 0 );
}

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