From 684fc27f6389f44102b5a3b31f62badc35a9a9ce Mon Sep 17 00:00:00 2001
From: Ben Burwell <ben@benburwell.com>
Date: Wed, 1 Apr 2015 20:32:27 -0400
Subject: as of 2013-12-04

---
 io.c | 192 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 192 insertions(+)
 create mode 100644 io.c

(limited to 'io.c')

diff --git a/io.c b/io.c
new file mode 100644
index 0000000..aa9b027
--- /dev/null
+++ b/io.c
@@ -0,0 +1,192 @@
+/*
+ * IO functionality
+ * for MPX-OS
+ * Ben Burwell & Averill Morash
+ * CSI350 - Fall 2013
+ */
+
+#include <dos.h>
+#include <stdio.h>
+#include "mpx.h"
+
+#define DS_OFFSET   6 // was 3 before
+
+int count = 0;
+void IO_sup(pcb *p) {
+  char far *buffer;
+  int far *length;
+  unsigned *ds_add;
+  int con_w = 0;
+  int rc;
+
+  disable();
+
+  if (DEBUG_PRINTS) { printf("in io_sup \n");}
+
+  //make the far pointers (see page 107)
+  ds_add = p->stack_ptr + DS_OFFSET;
+  buffer = MK_FP(*ds_add, p->parm_add->buffer);
+  length = MK_FP(*ds_add, p->parm_add->length);
+
+  //call com_read or equivalent
+  switch (p->parm_add->op_number){
+	case COM:
+	  // IO_sched should have validated input
+	  // Assume that op_type is either read or write
+	  if (p->parm_add->op_type == READ) {
+		 if (DEBUG_PRINTS){printf("com read req \n");}
+		 com_eflag = 0;
+		 rc = com_read(buffer, length);
+	  } else {
+		 if (DEBUG_PRINTS) {printf("com write req \n");}
+		 com_eflag = 0;
+		 rc = com_write(buffer, length);
+	  }
+	  break;
+	case CON:
+	  if (p->parm_add->op_type == READ) {
+		if (DEBUG_PRINTS){printf("con read req\n");}
+		con_eflag = 0;
+		con.current_op = READ_OP;
+		rc = con_read(buffer, length);
+	  } else {
+		if (DEBUG_PRINTS){printf("con_write req\n");}
+		con_w = 1;
+		rc = con_write(buffer, length);
+	  }
+	  break;
+	case PRT:
+	  if (DEBUG_PRINTS){printf("prt write req\n");}
+	  prt_eflag = 0;
+	  rc = prt_write(buffer, length);
+	  break;
+  }
+
+  if (rc < 0) {
+	printf("Somthing went wrong in io_sup\n");
+  }
+
+  // put the pcb back in the ready queue, if it was a con_write
+  if (con_w == 1) {
+	insert_pcb(&ready_queue_locked, p,0);
+  }
+  enable();
+  return;
+}
+
+// Handle completion of an IO request
+int IO_complete(int device, int *stk_ptr) {
+
+  pcb *current;
+  dcb *d;
+
+  disable();
+  switch (device){
+	case CON:
+	  d = &con;
+	  d->current_op = NO_OP;
+	  break;
+	case COM:
+	  d = &com;
+	  break;
+	case PRT:
+	  d = &prt;
+	  break;
+  }
+
+  if (DEBUG_PRINTS){printf("in io complete\n");}
+
+  // save interrupted process's stack pointer
+  cop->stack_ptr = stk_ptr;
+
+  // insert running process into ready queue
+  insert_pcb(&ready_queue_locked, cop, 0);
+
+  // set running process to ready state
+  cop->state = READY;
+
+  // get address of PCB whose IO just completed
+  current = d->current_pcb;
+
+  // insert into ready queue
+  insert_pcb(&ready_queue_locked, current, 0);
+
+  // set its state to ready
+  current->state = READY;
+
+  if (strcmp(d->current_pcb->name, "iocom2")==0) {
+	count++;
+	if (count > 20) {
+	d = &com;
+	}
+  }
+  if (d->pcb_head != NULL) {
+	// if there are pending IO requests for this device
+	//schedule them (IO_sched)
+	remove_pcb(&(d->pcb_head), d->pcb_head);
+	IO_sched(d->pcb_head);
+  }
+
+  outportb(0x20,0x20); // EOI signal
+  enable();
+  dispatch();
+
+  return 0;
+}
+
+// Service an IO request
+// Returns:
+//    0 for success
+//   -1 for invalid operation
+//   -2 for invalid device
+int IO_sched(pcb *p) {
+
+  dcb *d;
+  int op_num;
+  int op_type;
+
+  if (DEBUG_PRINTS) {printf("in io sched\n");}
+
+  // determine which device is requested
+  op_num = p->parm_add->op_number;
+  op_type = p->parm_add->op_type;
+
+  switch (op_num) {
+	case CON:
+	  if (op_type != READ
+		&& op_type != WRITE) {
+		  return -1;
+	  }
+	  d = &con;
+	  break;
+	case COM:
+	  if (op_type != READ
+		&& op_type != WRITE) {
+		  return -1;
+	  }
+	  d = &com;
+	  break;
+	case PRT:
+	  if (op_type != WRITE) {
+		return -1;
+	  }
+	  d = &prt;
+	  break;
+	default:
+	  return -2;
+  }
+
+  if (d->current_op != NO_OP) {
+	disable();
+	// put pcb in IO queue
+	insert_pcb(&(d->pcb_head), p, 1);
+	// take pcb out of ready q
+	remove_pcb(&ready_queue_locked, p);
+	enable();
+  } else {
+	d->current_pcb = p;
+	IO_sup(p);
+  }
+
+  return 0;
+}
-- 
cgit v1.2.3