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/*
Title: Bitmap. Generally used by the garbage collector to indicate allocated words
Copyright (c) 2006, 2012 David C.J. Matthews
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef BITMAP_H_DEFINED
#define BITMAP_H_DEFINED
#include "globals.h" // For POLYUNSIGNED
class Bitmap
{
public:
Bitmap(): m_bits(0) {}
~Bitmap();
// Allocate the bitmap bits
bool Create(POLYUNSIGNED bits);
// Free the bitmap bits.
void Destroy();
private:
static unsigned char BitN(POLYUNSIGNED n) { return 1 << (n & 7); }
public:
// Test to see if it has been created
bool Created() const { return m_bits != 0; }
// Set a single bit
void SetBit(POLYUNSIGNED n) { m_bits[n >> 3] |= BitN(n); }
// Clear a single bit
void ClearBit(POLYUNSIGNED n) { m_bits[n >> 3] &= (0xff ^ BitN(n)); }
// Set a range of bits
void SetBits(POLYUNSIGNED bitno, POLYUNSIGNED length);
// Clear a range of bits. May already be partly clear
// N.B. This may clear more than just the bits specified
void ClearBits(POLYUNSIGNED bitno, POLYUNSIGNED length);
// Test a bit
bool TestBit(POLYUNSIGNED n) const { return (m_bits[n >> 3] & BitN(n)) != 0; }
// How many zero bits (maximum n) are there in the bitmap, starting at location start?
POLYUNSIGNED CountZeroBits(POLYUNSIGNED bitno, POLYUNSIGNED n) const;
//* search the bitmap from the high end down looking for n contiguous zeros
POLYUNSIGNED FindFree(POLYUNSIGNED limit, POLYUNSIGNED bitno, POLYUNSIGNED n) const;
// How many set bits are there in the bitmap?
POLYUNSIGNED CountSetBits(POLYUNSIGNED size) const;
// Find the last set bit before here.
POLYUNSIGNED FindLastSet(POLYUNSIGNED bitno) const;
private:
unsigned char *m_bits;
};
// A wrapper class that adds the address range. It is used when scanning
// memory to see if an address has already been visited.
class VisitBitmap: public Bitmap
{
public:
VisitBitmap(PolyWord *bottom, PolyWord *top):
m_bottom(bottom), m_top(top) { (void)Create(top - bottom); }
bool AlreadyVisited(PolyObject *p) { return TestBit((PolyWord*)p - m_bottom); }
void SetVisited(PolyObject *p) { SetBit((PolyWord*)p - m_bottom); }
bool InRange(PolyWord *p) { return p >= m_bottom && p < m_top; }
protected:
PolyWord *m_bottom;
PolyWord *m_top;
};
#endif
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