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RCOS C++ CRC for class CpmFs

Name:

 CpmFs

Comment:

 Interface to the file system based on our old friend, the "port". Note how each file system operation takes a single XfReq pointer as input. The Single instance of class CpmFs receives requests for FS operations from user processes as messages. It merely creates a new XfReq object, filling in the originating PID and FCB pointer, determines which disk "unit" the request is for, checks that that unit is "on-line" and then calls the appropriate (protected) member function.

ALL calls to the File System result in the caller process becomming blocked. When the FS service is deemed to be complete, a result message will be posted to the PID (unblocking it) and the XfReq object killed off. The last member function of CpmBdos to be passed the XfReq pointer does this.

Note: it's each user process's responsibility to ensure the FCB is correctly initialised (by a successful call to FsOpen or FsCreat). The FS uses these FCB's to retain working data during file I/O operations. Looks to me now (in hindsight) that if you diddle with these, and you can trash the file system, big time. Funny, I don't recall that ever happening though (?)

Collaborators:

Responsibilities:

 class CpmFs : public port {
  private:
    CpmBdos *pUnit[MAX_DRIVES];         // Disk File System instances
  public:
    CpmFs (UINT16, UINT16, Knl*);       // register with kernel
   ~CpmFs (void);                       // murder all file systems
    void RxPort (PMSG);                 // supply virtual member of "port"
    void MountDrive (UINT16, char, DPB&, DPARAM&); // Instatiate new Bdos
  };