1 files changed, 83 insertions, 0 deletions
diff --git a/sys_sppt.c b/sys_sppt.c
new file mode 100644
index 0000000..be03d7d
--- /dev/null
+++ b/sys_sppt.c
@@ -0,0 +1,83 @@
+/***********************************************************************
+*
+*	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();
+}