Initial version

code/machine/translate.h

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+// translate.h 
+//	Data structures for managing the translation from 
+//	virtual page # -> physical page #, used for managing
+//	physical memory on behalf of user programs.
+//
+//	The data structures in this file are "dual-use" - they
+//	serve both as a page table entry, and as an entry in
+//	a software-managed translation lookaside buffer (TLB).
+//	Either way, each entry is of the form:
+//	<virtual page #, physical page #>.
+//
+// DO NOT CHANGE -- part of the machine emulation
+//
+// 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 TLB_H
+#define TLB_H
+
+#include "copyright.h"
+#include "utility.h"
+
+// The following class defines an entry in a translation table -- either
+// in a page table or a TLB.  Each entry defines a mapping from one 
+// virtual page to one physical page.
+// In addition, there are some extra bits for access control (valid and 
+// read-only) and some bits for usage information (use and dirty).
+
+class TranslationEntry {
+  public:
+    unsigned int virtualPage;  	// The page number in virtual memory, only when
+			// using a TLB
+    unsigned int physicalPage; 	// The page number in real memory (relative to the
+			//  start of "mainMemory"
+    bool valid;         // If this bit is cleared, the translation is ignored.
+			// (In other words, the entry hasn't been initialized.)
+    bool readOnly;	// If this bit is set, the user program is not allowed
+			// to modify the contents of the page.
+    bool use;           // This bit is set by the hardware every time the
+			// page is referenced or modified.
+    bool dirty;         // This bit is set by the hardware every time the
+			// page is modified.
+};
+
+#endif