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/***********************************************************************
*
* Name: sys_sppt.c
*
* Purpose: Support Routines for Modules 3 and 4 of MPX-PC
*
* Sample Call:
* sys_init()
* sys_exit()
*
* Procedures In Module:
* sys_init - Sets up interrupt vector 60 for MPX-PC
* sys_exit - Resets interrupt vector 60 and exits to DOS
*
*
****************************************************************************/
#include <stdio.h>
#include <dos.h>
#include "mpx.h"
void interrupt (*vect60)(); /* Storage for DOS int 60h */
/* interrupt vector. */
void sys_init()
{
/* set up interrupt vector for MPX sys_calls */
vect60 = getvect(0x60);
setvect(0x60,&sys_call);
}
void sys_exit()
{
/* restore interrupt vector 60 and exit */
setvect(0x60,vect60);
exit();
}
void interrupt dispatch()
{
/* your dispatcher code */
if (ready_queue == NULL) {
sys_exit();
} else {
cop = ready_queue; // make the front of the queue the running process
remove_pcb(&ready_queue, cop);
_SP = cop->stack_ptr;
}
}
void interrupt sys_call()
{
struct parm {
int op_number;
int op_type;
char *buffer;
int *length;
};
static struct parm *parm_add;
/* Save stack pointer for current process */
cop->stack_ptr = _SP;
/* Get address of sys_call parameters */
parm_add = _SP + 0x1c; // parameter offset = 0x1C
/* Note that you should save this parameter address
somewhere in the pcb as suggested below*/
cop->parm_add = parm_add;
// find out if the process wants to die... and kill it
if(parm_add->op_number != EXIT_CODE) {
insert_pcb(&ready_queue, cop, 0);
}
dispatch();
}
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