<android/bitmap.h>,Bitmap.h - Android社区 - https://www.androidos.net.cn/

西门安民
2023-12-01

/*

* Copyright (C) 2010 Apple Inc. All rights reserved.

*

* 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 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 Street, Fifth Floor, Boston, MA 02110-1301 USA

*

*/

#ifndef Bitmap_h

#define Bitmap_h

#include "FixedArray.h"

#include "StdLibExtras.h"

#include

#include

namespace WTF {

template

class Bitmap {

private:

typedef uint32_t WordType;

public:

Bitmap();

bool get(size_t) const;

void set(size_t);

bool testAndSet(size_t);

size_t nextPossiblyUnset(size_t) const;

void clear(size_t);

void clearAll();

int64_t findRunOfZeros(size_t) const;

size_t count(size_t = 0) const;

size_t isEmpty() const;

size_t isFull() const;

private:

static const WordType wordSize = sizeof(WordType) * 8;

static const WordType words = (size + wordSize - 1) / wordSize;

// the literal '1' is of type signed int. We want to use an unsigned

// version of the correct size when doing the calculations because if

// WordType is larger than int, '1 << 31' will first be sign extended

// and then casted to unsigned, meaning that set(31) when WordType is

// a 64 bit unsigned int would give 0xffff8000

static const WordType one = 1;

FixedArray bits;

};

template

inline Bitmap::Bitmap()

{

clearAll();

}

template

inline bool Bitmap::get(size_t n) const

{

return !!(bits[n / wordSize] & (one << (n % wordSize)));

}

template

inline void Bitmap::set(size_t n)

{

bits[n / wordSize] |= (one << (n % wordSize));

}

template

inline bool Bitmap::testAndSet(size_t n)

{

WordType mask = one << (n % wordSize);

size_t index = n / wordSize;

bool result = bits[index] & mask;

bits[index] |= mask;

return result;

}

template

inline void Bitmap::clear(size_t n)

{

bits[n / wordSize] &= ~(one << (n % wordSize));

}

template

inline void Bitmap::clearAll()

{

memset(bits.data(), 0, sizeof(bits));

}

template

inline size_t Bitmap::nextPossiblyUnset(size_t start) const

{

if (!~bits[start / wordSize])

return ((start / wordSize) + 1) * wordSize;

return start + 1;

}

template

inline int64_t Bitmap::findRunOfZeros(size_t runLength) const

{

if (!runLength)

runLength = 1;

for (size_t i = 0; i <= (size - runLength) ; i++) {

bool found = true;

for (size_t j = i; j <= (i + runLength - 1) ; j++) {

if (get(j)) {

found = false;

break;

}

}

if (found)

return i;

}

return -1;

}

template

inline size_t Bitmap::count(size_t start) const

{

size_t result = 0;

for ( ; (start % wordSize); ++start) {

if (get(start))

++result;

}

for (size_t i = start / wordSize; i < words; ++i)

result += WTF::bitCount(bits[i]);

return result;

}

template

inline size_t Bitmap::isEmpty() const

{

for (size_t i = 0; i < words; ++i)

if (bits[i])

return false;

return true;

}

template

inline size_t Bitmap::isFull() const

{

for (size_t i = 0; i < words; ++i)

if (~bits[i])

return false;

return true;

}

}

#endif

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