disk.h

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#ifndef DISK_H
#define DISK_H

#include "copyright.h"
#include "utility.h"

#define SectorSize      128 // number of bytes per disk sector
#define SectorsPerTrack     32  // number of sectors per disk track 
#define NumTracks       32  // number of tracks per disk
#define NumSectors      (SectorsPerTrack * NumTracks)
                    // total # of sectors per disk


class Disk {
  public:
    Disk(const char* name, VoidFunctionPtr callWhenDone, int callArg);
                        // Create a simulated disk.  
                    // Invoke (*callWhenDone)(callArg) 
                    // every time a request completes.
    ~Disk();                // Deallocate the disk.
    
    void ReadRequest(int sectorNumber, char* data);
                        // Read/write an single disk sector.
                    // These routines send a request to 
                        // the disk and return immediately.
                        // Only one request allowed at a time!
    void WriteRequest(int sectorNumber, char* data);

    void HandleInterrupt();     // Interrupt handler, invoked when
                    // disk request finishes.

    int ComputeLatency(int newSector, bool writing);    
                        // Return how long a request to 
                    // newSector will take: 
                    // (seek + rotational delay + transfer)

  private:
    int fileno;             // UNIX file number for simulated disk 
    VoidFunctionPtr handler;        // Interrupt handler, to be invoked 
                    // when any disk request finishes
    int handlerArg;         // Argument to interrupt handler 
    bool active;                // Is a disk operation in progress?
    int lastSector;         // The previous disk request 
    int bufferInit;         // When the track buffer started 
                    // being loaded

    int TimeToSeek(int newSector, int *rotate); // time to get to the new track
    int ModuloDiff(int to, int from);        // # sectors between to and from
    void UpdateLast(int newSector);
};

#endif // DISK_H