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/**
* Operating Systems
* Mod 6
* Averill and Ben
* Writing awesome printer stuff.
*/
#include <dos.h>
#include <stdio.h>
#include "mpx.h";
void interrupt (*vect0f)();
int prt_opened;
int prt_open(int * prt_flag) {
unsigned char imr;
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 far *length) {
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 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;
disable();
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
IO_complete(PRT, 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);
enable();
}
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