FileSystem class Reference

00081 { 
00082     DEBUG('f', "Initializing the file system.\n");
00083     if (format) {
00084         BitMap *freeMap = new BitMap(NumSectors);
00085         Directory *directory = new Directory(NumDirEntries);
00086         FileHeader *mapHdr = new FileHeader;
00087         FileHeader *dirHdr = new FileHeader;
00088 
00089         DEBUG('f', "Formatting the file system.\n");
00090 
00091     // First, allocate space for FileHeaders for the directory and bitmap
00092     // (make sure no one else grabs these!)
00093         freeMap->Mark(FreeMapSector);       
00094         freeMap->Mark(DirectorySector);
00095 
00096     // Second, allocate space for the data blocks containing the contents
00097     // of the directory and bitmap files.  There better be enough space!
00098 
00099         ASSERT(mapHdr->Allocate(freeMap, FreeMapFileSize));
00100         ASSERT(dirHdr->Allocate(freeMap, DirectoryFileSize));
00101 
00102     // Flush the bitmap and directory FileHeaders back to disk
00103     // We need to do this before we can "Open" the file, since open
00104     // reads the file header off of disk (and currently the disk has garbage
00105     // on it!).
00106 
00107         DEBUG('f', "Writing headers back to disk.\n");
00108         mapHdr->WriteBack(FreeMapSector);    
00109         dirHdr->WriteBack(DirectorySector);
00110 
00111     // OK to open the bitmap and directory files now
00112     // The file system operations assume these two files are left open
00113     // while Nachos is running.
00114 
00115         freeMapFile = new OpenFile(FreeMapSector);
00116         directoryFile = new OpenFile(DirectorySector);
00117      
00118     // Once we have the files "open", we can write the initial version
00119     // of each file back to disk.  The directory at this point is completely
00120     // empty; but the bitmap has been changed to reflect the fact that
00121     // sectors on the disk have been allocated for the file headers and
00122     // to hold the file data for the directory and bitmap.
00123 
00124         DEBUG('f', "Writing bitmap and directory back to disk.\n");
00125         freeMap->WriteBack(freeMapFile);         // flush changes to disk
00126         directory->WriteBack(directoryFile);
00127 
00128         if (DebugIsEnabled('f')) {
00129             freeMap->Print();
00130             directory->Print();
00131 
00132         delete freeMap; 
00133         delete directory; 
00134         delete mapHdr; 
00135         delete dirHdr;
00136         }
00137     } else {
00138     // if we are not formatting the disk, just open the files representing
00139     // the bitmap and directory; these are left open while Nachos is running
00140         freeMapFile = new OpenFile(FreeMapSector);
00141         directoryFile = new OpenFile(DirectorySector);
00142     }
00143 }

00176 {
00177     Directory *directory;
00178     BitMap *freeMap;
00179     FileHeader *hdr;
00180     int sector;
00181     bool success;
00182 
00183     DEBUG('f', "Creating file %s, size %d\n", name, initialSize);
00184 
00185     directory = new Directory(NumDirEntries);
00186     directory->FetchFrom(directoryFile);
00187 
00188     if (directory->Find(name) != -1)
00189       success = FALSE;                  // file is already in directory
00190     else {      
00191         freeMap = new BitMap(NumSectors);
00192         freeMap->FetchFrom(freeMapFile);
00193         sector = freeMap->Find();       // find a sector to hold the file header
00194         if (sector == -1)               
00195             success = FALSE;            // no free block for file header 
00196         else if (!directory->Add(name, sector))
00197             success = FALSE;    // no space in directory
00198         else {
00199             hdr = new FileHeader;
00200             if (!hdr->Allocate(freeMap, initialSize))
00201                 success = FALSE;        // no space on disk for data
00202             else {      
00203                 success = TRUE;
00204                 // everthing worked, flush all changes back to disk
00205                 hdr->WriteBack(sector);                 
00206                 directory->WriteBack(directoryFile);
00207                 freeMap->WriteBack(freeMapFile);
00208             }
00209             delete hdr;
00210         }
00211         delete freeMap;
00212     }
00213     delete directory;
00214     return success;
00215 }

00297 {
00298     Directory *directory = new Directory(NumDirEntries);
00299 
00300     directory->FetchFrom(directoryFile);
00301     directory->List();
00302     delete directory;
00303 }

00229 { 
00230     Directory *directory = new Directory(NumDirEntries);
00231     OpenFile *openFile = NULL;
00232     int sector;
00233 
00234     DEBUG('f', "Opening file %s\n", name);
00235     directory->FetchFrom(directoryFile);
00236     sector = directory->Find(name); 
00237     if (sector >= 0)            
00238         openFile = new OpenFile(sector);        // name was found in directory 
00239     delete directory;
00240     return openFile;                            // return NULL if not found
00241 }

00317 {
00318     FileHeader *bitHdr = new FileHeader;
00319     FileHeader *dirHdr = new FileHeader;
00320     BitMap *freeMap = new BitMap(NumSectors);
00321     Directory *directory = new Directory(NumDirEntries);
00322 
00323     printf("Bit map file header:\n");
00324     bitHdr->FetchFrom(FreeMapSector);
00325     bitHdr->Print();
00326 
00327     printf("Directory file header:\n");
00328     dirHdr->FetchFrom(DirectorySector);
00329     dirHdr->Print();
00330 
00331     freeMap->FetchFrom(freeMapFile);
00332     freeMap->Print();
00333 
00334     directory->FetchFrom(directoryFile);
00335     directory->Print();
00336 
00337     delete bitHdr;
00338     delete dirHdr;
00339     delete freeMap;
00340     delete directory;
00341 }

00259 { 
00260     Directory *directory;
00261     BitMap *freeMap;
00262     FileHeader *fileHdr;
00263     int sector;
00264     
00265     directory = new Directory(NumDirEntries);
00266     directory->FetchFrom(directoryFile);
00267     sector = directory->Find(name);
00268     if (sector == -1) {
00269        delete directory;
00270        return FALSE;                     // file not found 
00271     }
00272     fileHdr = new FileHeader;
00273     fileHdr->FetchFrom(sector);
00274 
00275     freeMap = new BitMap(NumSectors);
00276     freeMap->FetchFrom(freeMapFile);
00277 
00278     fileHdr->Deallocate(freeMap);               // remove data blocks
00279     freeMap->Clear(sector);                     // remove header block
00280     directory->Remove(name);
00281 
00282     freeMap->WriteBack(freeMapFile);            // flush to disk
00283     directory->WriteBack(directoryFile);        // flush to disk
00284     delete fileHdr;
00285     delete directory;
00286     delete freeMap;
00287     return TRUE;
00288 }

Public Methods
	FileSystem (bool format)
bool	Create (char *name, int initialSize)
OpenFile *	Open (char *name)
bool	Remove (char *name)
void	List ()
void	Print ()
Private Attributes
OpenFile *	freeMapFile
OpenFile *	directoryFile

FileSystem Class Reference

Public Methods

Private Attributes

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation