Directories

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.

List()

Print out the directory contents (debugging).

Print()

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