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directory.h

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// directory.h 
//      Data structures to manage a UNIX-like directory of file names.
// 
//      A directory is a table of pairs: <file name, sector #>,
//      giving the name of each file in the directory, and 
//      where to find its file header (the data structure describing
//      where to find the file's data blocks) on disk.
//
//      We assume mutual exclusion is provided by the caller.
//
// 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"

#ifndef DIRECTORY_H
#define DIRECTORY_H

#include "openfile.h"

#define FileNameMaxLen          9       // for simplicity, we assume 
                                        // file names are <= 9 characters long

// The following class defines a "directory entry", representing a file
// in the directory.  Each entry gives the name of the file, and where
// the file's header is to be found on disk.
//
// Internal data structures kept public so that Directory operations can
// access them directly.

class DirectoryEntry {
  public:
    bool inUse;                         // Is this directory entry in use?
    int sector;                         // Location on disk to find the 
                                        //   FileHeader for this file 
    char name[FileNameMaxLen + 1];      // Text name for file, with +1 for 
                                        // the trailing '\0'
};

// 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. 

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: 
                                        // <file name, file header location> 

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

#endif // DIRECTORY_H

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