Initial version

code/filesys/openfile.h

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+// openfile.h 
+//	Data structures for opening, closing, reading and writing to 
+//	individual files.  The operations supported are similar to
+//	the UNIX ones -- type 'man open' to the UNIX prompt.
+//
+//	There are two implementations.  One is a "STUB" that directly
+//	turns the file operations into the underlying UNIX operations.
+//	(cf. comment in filesys.h).
+//
+//	The other is the "real" implementation, that turns these
+//	operations into read and write disk sector requests. 
+//	In this baseline implementation of the file system, we don't 
+//	worry about concurrent accesses to the file system
+//	by different threads -- this is part of 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.
+
+#ifndef OPENFILE_H
+#define OPENFILE_H
+
+#include "copyright.h"
+#include "utility.h"
+
+#ifdef FILESYS_STUB			// Temporarily implement calls to 
+					// Nachos file system as calls to UNIX!
+					// See definitions listed under #else
+class OpenFile:public dontcopythis {
+  public:
+    OpenFile(int f) { file = f; currentOffset = 0; }	// open the file
+    ~OpenFile() { Close(file); file = -1; }			// close the file
+
+    int ReadAt(void *into, int numBytes, int position) { 
+    		Lseek(file, position, SEEK_SET); 
+		return ReadPartial(file, into, numBytes); 
+		}	
+    int WriteAt(const void *from, int numBytes, int position) { 
+    		Lseek(file, position, SEEK_SET); 
+		WriteFile(file, from, numBytes); 
+		return numBytes;
+		}	
+    int Read(void *into, int numBytes) {
+		int numRead = ReadAt(into, numBytes, currentOffset); 
+		currentOffset += numRead;
+		return numRead;
+    		}
+    int Write(const void *from, int numBytes) {
+		int numWritten = WriteAt(from, numBytes, currentOffset); 
+		currentOffset += numWritten;
+		return numWritten;
+		}
+
+    int Length() { Lseek(file, 0, SEEK_END); return Tell(file); }
+    
+  private:
+    int file;
+    int currentOffset;
+};
+
+#else // FILESYS
+class FileHeader;
+
+class OpenFile:public dontcopythis {
+  public:
+    OpenFile(int sector);		// Open a file whose header is located
+					// at "sector" on the disk
+    ~OpenFile();			// Close the file
+
+    void Seek(int position); 		// Set the position from which to 
+					// start reading/writing -- UNIX lseek
+
+    int Read(void *into, int numBytes); // Read/write bytes from the file,
+					// starting at the implicit position.
+					// Return the # actually read/written,
+					// and increment position in file.
+    int Write(const void *from, int numBytes);
+
+    int ReadAt(void *into, int numBytes, int position);
+    					// Read/write bytes from the file,
+					// bypassing the implicit position.
+					// Return the # actually read/written.
+    int WriteAt(const void *from, int numBytes, int position);
+
+    int Length(); 			// Return the number of bytes in the
+					// file (this interface is simpler 
+					// than the UNIX idiom -- lseek to 
+					// end of file, tell, lseek back 
+    
+  private:
+    FileHeader *hdr;			// Header for this file 
+    int seekPosition;			// Current position within the file
+};
+
+#endif // FILESYS
+
+#endif // OPENFILE_H