61 lines
2.1 KiB
C++
61 lines
2.1 KiB
C++
// bitmap.h
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// Data structures defining a bitmap -- an array of bits each of which
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// can be either on or off.
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//
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// Represented as an array of unsigned integers, on which we do
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// modulo arithmetic to find the bit we are interested in.
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//
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// The bitmap can be parameterized with with the number of bits being
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// managed.
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//
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// Copyright (c) 1992-1993 The Regents of the University of California.
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// All rights reserved. See copyright.h for copyright notice and limitation
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// of liability and disclaimer of warranty provisions.
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#ifndef BITMAP_H
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#define BITMAP_H
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#include "copyright.h"
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#include "utility.h"
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#include "openfile.h"
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// The following class defines a "bitmap" -- an array of bits,
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// each of which can be independently set, cleared, and tested.
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//
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// Most useful for managing the allocation of the elements of an array --
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// for instance, disk sectors, or main memory pages.
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// Each bit represents whether the corresponding sector or page is
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// in use or free.
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class BitMap:public dontcopythis
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{
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public:
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BitMap (int nitems); // Initialize a bitmap, with "nitems" bits
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// initially, all bits are cleared.
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~BitMap (); // De-allocate bitmap
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void Mark (int which); // Set the "nth" bit
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void Clear (int which); // Clear the "nth" bit
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bool Test (int which); // Is the "nth" bit set?
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int Find (); // Return the # of a clear bit, and as a side
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// effect, set the bit.
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// If no bits are clear, return -1.
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int NumClear (); // Return the number of clear bits
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void Print (); // Print contents of bitmap
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// These aren't needed until FILESYS, when we will need to read and
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// write the bitmap to a file
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void FetchFrom (OpenFile * file); // fetch contents from disk
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void WriteBack (OpenFile * file); // write contents to disk
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private:
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int numBits; // number of bits in the bitmap
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int numWords; // number of words of bitmap storage
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// (rounded up if numBits is not a
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// multiple of the number of bits in
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// a word)
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unsigned int *map; // bit storage
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};
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#endif // BITMAP_H
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