// console.cc //	Routines to simulate a serial port to a console device.//	A console has input (a keyboard) and output (a display).//	These are each simulated by operations on UNIX files.//	The simulated device is asynchronous,//	so we have to invoke the interrupt handler (after a simulated//	delay), to signal that a byte has arrived and/or that a written//	byte has departed.////  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.#include "copyright.h"#include "console.h"#include "system.h"// Dummy functions because C++ is weird about pointers to member functionsstatic void ConsoleReadPoll(int c) { Console *console = (Console *)c; console->CheckCharAvail(); }static void ConsoleWriteDone(int c){ Console *console = (Console *)c; console->WriteDone(); }//----------------------------------------------------------------------// Console::Console// 	Initialize the simulation of a hardware console device.////	"readFile" -- UNIX file simulating the keyboard (NULL -> use stdin)//	"writeFile" -- UNIX file simulating the display (NULL -> use stdout)// 	"readAvail" is the interrupt handler called when a character arrives//		from the keyboard// 	"writeDone" is the interrupt handler called when a character has//		been output, so that it is ok to request the next char be//		output//----------------------------------------------------------------------Console::Console(char *readFile, char *writeFile, VoidFunctionPtr readAvail, 		VoidFunctionPtr writeDone, int callArg){    if (readFile == NULL)	readFileNo = 0;					// keyboard = stdin    else    	readFileNo = OpenForReadWrite(readFile, TRUE);	// should be read-only    if (writeFile == NULL)	writeFileNo = 1;				// display = stdout    else    	writeFileNo = OpenForWrite(writeFile);    // set up the stuff to emulate asynchronous interrupts    writeHandler = writeDone;    readHandler = readAvail;    handlerArg = callArg;    putBusy = FALSE;    incoming = EOF;    // start polling for incoming packets    interrupt->Schedule(ConsoleReadPoll, (int)this, ConsoleTime, ConsoleReadInt);}//----------------------------------------------------------------------// Console::~Console// 	Clean up console emulation//----------------------------------------------------------------------Console::~Console(){    if (readFileNo != 0)	Close(readFileNo);    if (writeFileNo != 1)	Close(writeFileNo);}//----------------------------------------------------------------------// Console::CheckCharAvail()// 	Periodically called to check if a character is available for//	input from the simulated keyboard (eg, has it been typed?).////	Only read it in if there is buffer space for it (if the previous//	character has been grabbed out of the buffer by the Nachos kernel).//	Invoke the "read" interrupt handler, once the character has been //	put into the buffer. //----------------------------------------------------------------------voidConsole::CheckCharAvail(){    char c;    // schedule the next time to poll for a packet    interrupt->Schedule(ConsoleReadPoll, (int)this, ConsoleTime, 			ConsoleReadInt);    // do nothing if character is already buffered, or none to be read    if ((incoming != EOF) || !PollFile(readFileNo))	return;	      // otherwise, read character and tell user about it    Read(readFileNo, &c, sizeof(char));    incoming = c ;    stats->numConsoleCharsRead++;    (*readHandler)(handlerArg);	}//----------------------------------------------------------------------// Console::WriteDone()// 	Internal routine called when it is time to invoke the interrupt//	handler to tell the Nachos kernel that the output character has//	completed.//----------------------------------------------------------------------voidConsole::WriteDone(){    putBusy = FALSE;    stats->numConsoleCharsWritten++;    (*writeHandler)(handlerArg);}//----------------------------------------------------------------------// Console::GetChar()// 	Read a character from the input buffer, if there is any there.//	Either return the character, or EOF if none buffered.//----------------------------------------------------------------------charConsole::GetChar(){   char ch = incoming;   incoming = EOF;   return ch;}//----------------------------------------------------------------------// Console::PutChar()// 	Write a character to the simulated display, schedule an interrupt //	to occur in the future, and return.//----------------------------------------------------------------------voidConsole::PutChar(char ch){    ASSERT(putBusy == FALSE);    WriteFile(writeFileNo, &ch, sizeof(char));    putBusy = TRUE;    interrupt->Schedule(ConsoleWriteDone, (int)this, ConsoleTime,					ConsoleWriteInt);}