60 lines
2.0 KiB
C++
60 lines
2.0 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) 1992-1996 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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// Definitions helpful for representing a bitmap as an array of integers
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const int BitsInByte = 8;
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const int BitsInWord = sizeof(unsigned int) * BitsInByte;
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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 {
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public:
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Bitmap(int numItems); // Initialize a bitmap, with "numItems" 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) const; // Is the "nth" bit set?
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int FindAndSet(); // 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() const; // Return the number of clear bits
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void Print() const; // Print contents of bitmap
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void SelfTest(); // Test whether bitmap is working
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protected:
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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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