as of 2013-12-062013-12-06

1 files changed, 47 insertions, 8 deletions

diff --git a/com.c b/com.c
index 1d21a0a..d996e66 100644
--- a/com.c
+++ b/com.c
@@ -3,7 +3,8 @@
  * CSI350 Operating Systems

  * Fall 2013

  * Averill Morash, Ben Burwell

- * COM.C

+ *

+ * File: com.c

  */

 

 #include <dos.h>

@@ -16,6 +17,7 @@ void interrupt (*vect0c)();
 

 int com_opened;

 

+// Open the com port

 int com_open(int * flag, int rate) {

   unsigned char imr;

   unsigned char mcr;

@@ -24,13 +26,15 @@ int com_open(int * flag, int rate) {
 

   disable();

 

+  // Ensure com has not already been opened, if

+  // it has, we must return.

   if (com_opened == NULL || com_opened == 0) {

 	com_opened = 1;

   } else {

 	return -2;

   }

 

-  // modify the interrupt vector table

+  // Modify the interrupt vector table

   vect0c = getvect(0x0c);

   setvect(0x0c, &com_int);

 

@@ -48,6 +52,7 @@ int com_open(int * flag, int rate) {
   // 1843200 / (1200 * 16) = 96 = 0x0060

   // So the MSB is 0x00 and the LSB is 0x60

 

+  // Ensure baud rate is valid

   if (rate != 1200) {

 	return -3;

   }

@@ -97,17 +102,27 @@ int com_open(int * flag, int rate) {
   return 0;

 }

 

+// Com Close

 void com_close() {

   disable();

+

+  // restore MS-DOS com vector

   setvect(0x0c, vect0c);

+

   enable();

 }

 

+// Interrupt handler

 void interrupt com_int() {

   int iir;

   int *lst_stk;

-  int ret = 0; //0 indicates not finished, 1 indicated finshed

 

+  // 0 indicates not finished, 1 indicated finshed

+  int ret = 0;

+

+  disable();

+

+  // save base pointer

   lst_stk = _BP;

 

   // check IIR to see what caused the interrupt

@@ -120,10 +135,11 @@ void interrupt com_int() {
   } else if (iir == 0x04) { // 0000-0100

 	ret = com_read_int();

   } else {

-	// something is wrong

+	// interrupt was not read or write

 	return;

   }

 

+  // if the operation is done, call IO_complete

   if (ret == 1) {

 	IO_complete(COM, lst_stk);

   }

@@ -131,70 +147,92 @@ void interrupt com_int() {
   // write end of interrupt to 8259

   outportb(0x20, 0x20);

 

+  enable();

   return;

 

 }

 

+// Read from the com port

 int com_read(char far * buffer, int far * length) {

 

   char dq;

   int i;

 

+  disable();

+

+  // if we haven't yet opened com, we can't proceed

   if (&com == NULL) {

-	// com not yet open

+	enable();

 	return -1;

   }

 

   // check for invalid length

   if (*length < 1) {

+	enable();

 	return -3;

   }

 

   // check if DCB is free

   if (com.current_op != NO_OP) {

 	// previous IO not yet complete

-	// TODO: we should block this process

+	enable();

 	return -2;

   }

 

+  if (buffer == NULL || length == NULL) {

+	printf("error in com_read\n");

+	enable();

+	return;

+  }

+  // set up the DCB

   com.buffer = buffer;

   com.length = length;

   com.current_op = READ_OP;

   com.count = 0;

 

+  // clear the buffer

   strcpy(buffer, "");

 

+  // now we need to use the ring buffer to place typed-ahead

+  // characters into the buffer

+

+  // keep track of how many characters are copied from the

+  // ring buffer.

   i = 0;

 

   while (com.ring_count > 0 && strlen(buffer) < *length) {

-

 	dq = dcb_dequeue(&com);

-	//strcat(buffer, &dq);

 	buffer[i] = dq;

 	i++;

   }

 

+  // place a null character at the end of the buffer

   buffer[i] = '\0';

   com.count = i;

 

+  enable();

   return 0;

 }

 

 int com_write(char far * buffer, int far * length) {

   int ier;

 

+  disable();

   // check that com has been initialized

   if (&com == NULL) {

+	enable();

 	return -1;

   }

 

   // check that com is not busy

   if (com.current_op != NO_OP) {

+	enable();

 	return -2;

   }

 

   // check that the length is valid

   if (*length < 1) {

+	enable();

 	return -3;

   }

 

@@ -210,6 +248,7 @@ int com_write(char far * buffer, int far * length) {
   ier = ier | 0x02;

   outportb(IER, ier);

 

+  enable();

   return 0;

 }