// console.h 
//	Data structures to simulate the behavior of a terminal
//	I/O device.  A terminal has two parts -- a keyboard input,
//	and a display output, each of which produces/accepts 
//	characters sequentially.
//
//	The console hardware device is asynchronous.  When a character is
//	written to the device, the routine returns immediately, and an 
//	interrupt handler is called later when the I/O completes.
//	For reads, an interrupt handler is called when a character arrives. 
//
//	The user of the device can specify the routines to be called when 
//	the read/write interrupts occur.  There is a separate interrupt
//	for read and write, and the device is "duplex" -- a character
//	can be outgoing and incoming at the same time.
//
//  DO NOT CHANGE -- part of the machine emulation
//
// Copyright (c) 1992-1993 The Regents of the University of California.
// All rights reserved.  See copyright.h for copyright notice and limitation 
// of liability and disclaimer of warranty provisions.

#ifndef CONSOLE_H
#define CONSOLE_H

#include "copyright.h"
#include "utility.h"
#include <stdio.h>

// The following class defines a hardware console device.
// Input and output to the device is simulated by reading 
// and writing to UNIX files ("readFile" and "writeFile").
//
// Since the device is asynchronous, the interrupt handler "readAvailHandler" 
// is called when a character has arrived, ready to be read by calling
// RX().
// The interrupt handler "writeDone" is called when an output character written
// by calling TX() has been "put", so that the next character can be
// written.

class Console:public dontcopythis {
  public:
    Console(const char *readFile, const char *writeFile, VoidFunctionPtr readAvailHandler, 
	VoidFunctionPtr writeDoneHandler, void *callArg);
				// initialize the hardware console device,
				// registers the readAvailHandler and writeDoneHandler
				// callbacks

    ~Console();			// clean up console emulation

// external interface -- Nachos kernel code can call these
    void TX(int ch);		// Write "ch" to the console display, 
				// and return immediately.  "writeDone" 
				// is called when the I/O completes. 

    int RX();		   	// Poll the console input.  If a char is 
				// available, return it.  Otherwise, crash.
				// EOF is returned if the end of the input
				// file was reached.
    				// "readDone" is called whenever there is 
				// a char to be gotten

// internal emulation routines -- DO NOT call these. 
    void WriteDone();	 	// internal routines to signal I/O completion
    void CheckCharAvail();

  private:
    int readFileNo;			// UNIX file emulating the keyboard 
    int writeFileNo;			// UNIX file emulating the display
    VoidFunctionPtr writeHandler; 	// Interrupt handler to call when 
					// the TX I/O completes
    VoidFunctionPtr readHandler; 	// Interrupt handler to call when 
					// a character arrives from the keyboard
    void *handlerArg;			// argument to be passed to the 
					// interrupt handlers
    bool putBusy;    			// Is a TX operation in progress?
					// If so, you can't do another one!
    int incoming;    			// Contains the character to be read,
					// if there is one available. 
					// Otherwise contains EOF.
    static int stdin_busy;		// Whether stdin is already read from
					// by a console.
};

#endif // CONSOLE_H