Initial version

code/filesys/directory.cc

@@ -0,0 +1,198 @@
+// directory.cc 
+//	Routines to manage a directory of file names.
+//
+//	The directory is a table of fixed length entries; each
+//	entry represents a single file, and contains the file name,
+//	and the location of the file header on disk.  The fixed size
+//	of each directory entry means that we have the restriction
+//	of a fixed maximum size for file names.
+//
+//	The constructor initializes an empty directory of a certain size;
+//	we use ReadFrom/WriteBack to fetch the contents of the directory
+//	from disk, and to write back any modifications back to disk.
+//
+//	Also, this implementation has the restriction that the size
+//	of the directory cannot expand.  In other words, once all the
+//	entries in the directory are used, no more files can be created.
+//	Fixing this is one of the parts to the assignment.
+//
+// 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"
+#include "utility.h"
+#include "filehdr.h"
+#include "directory.h"
+
+//----------------------------------------------------------------------
+// Directory::Directory
+// 	Initialize a directory; initially, the directory is completely
+//	empty.  If the disk is being formatted, an empty directory
+//	is all we need, but otherwise, we need to call FetchFrom in order
+//	to initialize it from disk.
+//
+//	"size" is the number of entries in the directory
+//----------------------------------------------------------------------
+
+Directory::Directory(int size)
+{
+    table = new DirectoryEntry[size];
+    tableSize = size;
+    for (int i = 0; i < tableSize; i++)
+	table[i].inUse = FALSE;
+}
+
+//----------------------------------------------------------------------
+// Directory::~Directory
+// 	De-allocate directory data structure.
+//----------------------------------------------------------------------
+
+Directory::~Directory()
+{ 
+    delete [] table;
+    table = NULL;
+} 
+
+//----------------------------------------------------------------------
+// Directory::FetchFrom
+// 	Read the contents of the directory from disk.
+//
+//	"file" -- file containing the directory contents
+//----------------------------------------------------------------------
+
+void
+Directory::FetchFrom(OpenFile *file)
+{
+    (void) file->ReadAt(table, tableSize * sizeof(DirectoryEntry), 0);
+}
+
+//----------------------------------------------------------------------
+// Directory::WriteBack
+// 	Write any modifications to the directory back to disk
+//
+//	"file" -- file to contain the new directory contents
+//----------------------------------------------------------------------
+
+void
+Directory::WriteBack(OpenFile *file)
+{
+    (void) file->WriteAt(table, tableSize * sizeof(DirectoryEntry), 0);
+}
+
+//----------------------------------------------------------------------
+// Directory::FindIndex
+// 	Look up file name in directory, and return its location in the table of
+//	directory entries.  Return -1 if the name isn't in the directory.
+//
+//	"name" -- the file name to look up
+//----------------------------------------------------------------------
+
+int
+Directory::FindIndex(const char *name)
+{
+    for (int i = 0; i < tableSize; i++)
+        if (table[i].inUse && !strncmp(table[i].name, name, FileNameMaxLen))
+	    return i;
+    return -1;		// name not in directory
+}
+
+//----------------------------------------------------------------------
+// Directory::Find
+// 	Look up file name in directory, and return the disk sector number
+//	where the file's header is stored. Return -1 if the name isn't 
+//	in the directory.
+//
+//	"name" -- the file name to look up
+//----------------------------------------------------------------------
+
+int
+Directory::Find(const char *name)
+{
+    int i = FindIndex(name);
+
+    if (i != -1)
+	return table[i].sector;
+    return -1;
+}
+
+//----------------------------------------------------------------------
+// Directory::Add
+// 	Add a file into the directory.  Return TRUE if successful;
+//	return FALSE if the file name is already in the directory, or if
+//	the directory is completely full, and has no more space for
+//	additional file names.
+//
+//	"name" -- the name of the file being added
+//	"newSector" -- the disk sector containing the added file's header
+//----------------------------------------------------------------------
+
+bool
+Directory::Add(const char *name, int newSector)
+{ 
+    if (FindIndex(name) != -1)
+	return FALSE;
+
+    for (int i = 0; i < tableSize; i++)
+        if (!table[i].inUse) {
+            table[i].inUse = TRUE;
+            strncpy(table[i].name, name, FileNameMaxLen); 
+            table[i].sector = newSector;
+        return TRUE;
+	}
+    return FALSE;	// no space.  Fix when we have extensible files.
+}
+
+//----------------------------------------------------------------------
+// Directory::Remove
+// 	Remove a file name from the directory.  Return TRUE if successful;
+//	return FALSE if the file isn't in the directory. 
+//
+//	"name" -- the file name to be removed
+//----------------------------------------------------------------------
+
+bool
+Directory::Remove(const char *name)
+{ 
+    int i = FindIndex(name);
+
+    if (i == -1)
+	return FALSE; 		// name not in directory
+    table[i].inUse = FALSE;
+    return TRUE;	
+}
+
+//----------------------------------------------------------------------
+// Directory::List
+// 	List all the file names in the directory. 
+//----------------------------------------------------------------------
+
+void
+Directory::List()
+{
+   for (int i = 0; i < tableSize; i++)
+	if (table[i].inUse)
+	    printf("%s\n", table[i].name);
+}
+
+//----------------------------------------------------------------------
+// Directory::Print
+// 	List all the file names in the directory, their FileHeader locations,
+//	and the contents of each file.  For debugging.
+//----------------------------------------------------------------------
+
+void
+Directory::Print()
+{ 
+    FileHeader *hdr = new FileHeader;
+
+    printf("Directory contents:\n");
+    for (int i = 0; i < tableSize; i++)
+	if (table[i].inUse) {
+	    printf("Name: %s, Sector: %d\n", table[i].name, table[i].sector);
+	    hdr->FetchFrom(table[i].sector);
+	    hdr->Print();
+	}
+    printf("\n");
+    delete hdr;
+}