1 files changed, 157 insertions, 0 deletions
diff --git a/printer.c b/printer.c
new file mode 100644
index 0000000..840d811
--- /dev/null
+++ b/printer.c
@@ -0,0 +1,157 @@
+/**
+ *  Operating Systems
+ *  Mod 6
+ *  Averill and Ben
+ *  Writing awesome printer stuff.
+ */
+
+#include <dos.h>
+#include <stdio.h>
+#include "mpx.h";
+
+void interrupt (*vect0f)();
+dcb prt;
+
+int prt_opened;
+
+int prt_open(int * prt_flag) {
+  unsigned char imr;
+  unsigned char pcr;
+
+  disable();
+
+  if (prt_opened == NULL || prt_opened == 0) {
+	prt_opened = 1;
+  } else {
+	return -2;
+  }
+
+  // set up vector interrupt
+  vect0f = getvect(0x0f);
+  setvect(0x0f, &prt_int);
+
+  // enable printer interrupts on 8259
+  imr = inportb(IMR);
+  imr = imr & 0x7f; //0111-1111
+  outportb(IMR, imr);
+
+  // clear init bit (b2), set select bit (b3)
+  // 0000 1010
+  outportb(PCR, 0x0a);
+
+  // initialize a printer control block
+  prt.current_op = NO_OP;
+  prt.event_flag = prt_flag;
+  prt.count = 0;
+
+  enable();
+  return 0;
+}
+
+int prt_write(char far *buffer, int *length) {
+  unsigned char pcr;
+
+  disable();
+  // check that prt isn't busy
+  if (prt.current_op != NO_OP) {
+	return -2;
+  }
+
+  // check that length is valid
+  if (*length < 1) {
+	return -3;
+  }
+
+  //save buffer and length in prt dcb
+  prt.buffer = buffer;
+  prt.length = length;
+  prt.current_op = WRITE_OP;
+  prt.count = 0;
+
+  // enable printer interrupts on PCR
+  // 0001 1010
+  outportb(PCR, 0x1a);
+
+  // strobe printer
+  // 0001 1011
+  outportb(PCR, 0x1d);
+
+  // print a null
+  // NOTE: something is not right here because when i print something
+  // other than a null it still doesn't print
+  outportb(PDR, 0x00);
+
+  // unstrobe printer
+  // 0001 1010
+  outportb(PCR, 0x1c);
+
+  enable();
+  return 0;
+}
+
+int prt_close() {
+  unsigned char pcr;
+  unsigned char imr;
+
+  disable();
+
+  // reset printer
+  // set init bit (b2) to 1 all else clear
+  // 0000 0100
+  outportb(PCR, 0x04);
+
+  //disable printer interrupts
+  imr = inportb(IMR);
+  imr = imr | 0x80;
+  outportb(IMR, imr);
+
+  // restore ms-dos's printer interrupt vector
+  setvect(0x0f, vect0f);
+
+  enable();
+  return 0;
+}
+
+void interrupt prt_int() {
+  unsigned char pcr;
+  int *lst_stk;
+  float temp;
+
+  lst_stk = _BP;
+
+  // if no more char to write
+  if (prt.count == *(prt.length)) {
+	// disable printer interrupts at PCR
+	// clear b4 on PCR
+	pcr = inportb(PCR);
+	pcr = pcr & 0xef; // 1110-1111
+	outportb(PCR, pcr);
+
+	// set event flag
+	prt.current_op = NO_OP;
+	*(prt.event_flag) = 1;
+
+	// call io-complete
+	// TODO: the book says (pg 86) that there should be stuff passed to io-complete
+	IO_complete(2, lst_stk);
+
+	// send end of interrupt signal
+	outportb(0x20, 0x20);
+  } else {
+
+	// strobe printer
+	// 0001 1101
+	outportb(PCR, 0x1d);
+
+	// write char to PDR
+	outportb(PDR, prt.buffer[prt.count]);
+	prt.count++;
+
+	// unstrobe printer
+	// 0001 1100
+	outportb(PCR, 0x1c);
+  }
+
+  // send EOI
+  outportb(0x20, 0x20);
+}
+\ No newline at end of file