Initial version

code/userprog/bitmap.h

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+// bitmap.h 
+//      Data structures defining a bitmap -- an array of bits each of which
+//      can be either on or off.
+//
+//      Represented as an array of unsigned integers, on which we do
+//      modulo arithmetic to find the bit we are interested in.
+//
+//      The bitmap can be parameterized with with the number of bits being 
+//      managed.
+//
+// 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 BITMAP_H
+#define BITMAP_H
+
+#include "copyright.h"
+#include "utility.h"
+#include "openfile.h"
+
+// The following class defines a "bitmap" -- an array of bits,
+// each of which can be independently set, cleared, and tested.
+//
+// Most useful for managing the allocation of the elements of an array --
+// for instance, disk sectors, or main memory pages.
+// Each bit represents whether the corresponding sector or page is
+// in use or free.
+
+class BitMap:public dontcopythis
+{
+  public:
+    BitMap (int nitems);	// Initialize a bitmap, with "nitems" bits
+    // initially, all bits are cleared.
+     ~BitMap ();		// De-allocate bitmap
+
+    void Mark (int which);	// Set the "nth" bit
+    void Clear (int which);	// Clear the "nth" bit
+    bool Test (int which);	// Is the "nth" bit set?
+    int Find ();		// Return the # of a clear bit, and as a side
+    // effect, set the bit. 
+    // If no bits are clear, return -1.
+    int NumClear ();		// Return the number of clear bits
+
+    void Print ();		// Print contents of bitmap
+
+    // These aren't needed until FILESYS, when we will need to read and 
+    // write the bitmap to a file
+    void FetchFrom (OpenFile * file);	// fetch contents from disk 
+    void WriteBack (OpenFile * file);	// write contents to disk
+
+  private:
+    int numBits;		// number of bits in the bitmap
+    int numWords;		// number of words of bitmap storage
+    // (rounded up if numBits is not a
+    //  multiple of the number of bits in
+    //  a word)
+    unsigned int *map;		// bit storage
+};
+
+#endif // BITMAP_H