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Console CRC

Name:

 Console

Comment:

 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 "readAvail" is called when a character has arrived, ready to be read in. The interrupt handler "writeDone" is called when an output character has been "put", so that the next character can be written.

Collaborators:

Responsibilities: 

class Console {
  public:
    Console(char *readFile, char *writeFile, VoidFunctionPtr readAvail,
        VoidFunctionPtr writeDone, int callArg);
                                // initialize the hardware console device
    ~Console();                 // clean up console emulation

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

    char GetChar();             // Poll the console input.  If a char is
                                // available, return it.  Otherwise, return EOF.
                                // "readHandler" 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 PutChar I/O completes
    VoidFunctionPtr readHandler;        // Interrupt handler to call when
                                        // a character arrives from the keyboard
    int handlerArg;                     // argument to be passed to the
                                        // interrupt handlers
    bool putBusy;                       // Is a PutChar operation in progress?
                                        // If so, you can't do another one!
    char incoming;                      // Contains the character to be read,
                                        // if there is one available.
                                        // Otherwise contains EOF.
};