///
//	Hacking around.  J Pitts www.playstation.co.uk/~Sig1LL
//	29-9-97
///
// This shows how to install an exception handler before the psx kernel
// gets control.  You can then grab things like bus errors etc.
// You could also trap all system calls, and hopefully some decent timers.
//  The incentive for doing this is to get a good timer suitable for a
// music player that would be constant for both NTSC and PAL.
// For descriptions of the CAUSE and SR registers look in r3000.h
//
//  -Jim

//
//  Next weeks lesson.  How to install your own drivers into the kernel
//  event tables.
//

#include <libps.h>

extern void ExceptionHandler(void);
extern void ExceptionHandlerEnd(void);
extern void OldHandler(void);
extern void OldHandlerEnd(void);


// This should be called for every exception so don't hang around!
// I think most exceptions so far come from the vsync.
void CallBack(long a0, long a1){
    printf ("CAUSE(%x) SR(%x)\n", a0, a1);
}

///
///
///
void main(void){
    int i;

    long *dest, *src;

 // install our new handler

    dest = (long*)0x80000080;
    src = (long*)ExceptionHandler;

    EnterCriticalSection();

    while (src <= (long*)ExceptionHandlerEnd){
	*dest++ = *src++;
    }

    ExitCriticalSection();

// let something happen

    VSync(30);		

// restore a reasonable handler
// its not actually the orig, but its a opcode shorter. ;-)

    dest = (long*)0x80000080;
    src = (long*)OldHandler;

    EnterCriticalSection();

    while (src <= (long*)OldHandlerEnd){
	*dest++ = *src++;
    }

    ExitCriticalSection();

}