[ RCOS.java Home | RCOS Home | David's Home ]

Directory CRC

Name:

 Directory

Comment:

 The following class defines a UNIX-like "directory". Each entry in the directory describes a file, and where to find it on disk.

The directory data structure can be stored in memory, or on disk. When it is on disk, it is stored as a regular Nachos file.

The constructor initializes a directory structure in memory; the FetchFrom/WriteBack operations shuffle the directory information from/to disk.

Collaborators:

Responsibilities: 

class Directory {
  public:
    Directory(int size);                // Initialize an empty directory
                                        // with space for "size" files
    ~Directory();                       // De-allocate the directory

    void FetchFrom(OpenFile *file);     // Init directory contents from disk
    void WriteBack(OpenFile *file);     // Write modifications to
                                        // directory contents back to disk

    int Find(char *name);               // Find the sector number of the
                                        // FileHeader for file: "name"

    bool Add(char *name, int newSector);  // Add a file name into the directory

    bool Remove(char *name);            // Remove a file from the directory

    void List();                        // Print the names of all the files
                                        //  in the directory
    void Print();                       // Verbose print of the contents
                                        //  of the directory -- all the file
                                        //  names and their contents.

  private:
    int tableSize;                      // Number of directory entries
    DirectoryEntry *table;              // Table of pairs:
                                        // 

    int FindIndex(char *name);          // Find the index into the directory
                                        //  table corresponding to "name"
};