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Nachos supports a single top-level directory, managed by the Directory object. When a file is created, it is added to the directory; likewise, deleting a file results in its removal from the directory. Directory entries themselves consist of (filename, fnode, free_flag) triplets, with the free_flag indicating whether that directory slot is currently allocated. The following directory operations are supported:

Directory(int size):
This constructor creates an (in-memory) directory object capable of holding size entries.

void FetchFrom(OpenFile *file):
Fetch the directory contents stored in file file.

void WriteBack(OpenFile *file):
Flush the contents of the directory to the file file.

int Find(char *name):
Search the directory for a file called name, returning its fnode number if the file exists.

bool Add(char *name, int newSector):
Add the file name with fnode newSector to the directory. Note that this routine only updates the in-memory copy of the directory. To make the directory changes permanent, WriteBack must subsequently be invoked.

bool Remove(char *name):
Remove file name from the directory. Note that the Remove operator simply updates the directory; the FileHeader and data sectors associated with name are deallocated separately. In addition, a subsequent call to WriteBack is needed to make the changes permanent.

Print out the directory contents (debugging).

Print out contents of all files in the directory (debugging).

Thomas Narten
Mon Feb 3 15:00:27 EST 1997