152 lines
3.5 KiB
C++
152 lines
3.5 KiB
C++
/*
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* \brief Allocator using bitmaps
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* \author Alexander Boettcher
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* \author Stefan Kalkowski
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* \date 2012-06-14
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*/
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/*
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* Copyright (C) 2012-2013 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU General Public License version 2.
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*/
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#ifndef _INCLUDE__UTIL__BIT_ARRAY_H_
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#define _INCLUDE__UTIL__BIT_ARRAY_H_
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#include <util/string.h>
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#include <base/exception.h>
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#include <base/stdint.h>
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namespace Genode {
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class Bit_array_base
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{
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public:
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class Invalid_bit_count : public Exception {};
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class Invalid_index_access : public Exception {};
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class Invalid_clear : public Exception {};
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class Invalid_set : public Exception {};
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protected:
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static constexpr size_t _BITS_PER_BYTE = 8UL;
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static constexpr size_t _BITS_PER_WORD = sizeof(addr_t) *
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_BITS_PER_BYTE;
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private:
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unsigned _bit_cnt;
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unsigned _word_cnt;
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addr_t *_words;
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addr_t _word(addr_t index) const {
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return index / _BITS_PER_WORD; }
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void _check_range(addr_t const index,
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addr_t const width) const
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{
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if ((index >= _word_cnt * _BITS_PER_WORD) ||
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width > _word_cnt * _BITS_PER_WORD ||
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_word_cnt * _BITS_PER_WORD - width < index)
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throw Invalid_index_access();
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}
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addr_t _mask(addr_t const index, addr_t const width,
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addr_t &rest) const
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{
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addr_t const shift = index - _word(index) * _BITS_PER_WORD;
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rest = width + shift > _BITS_PER_WORD ?
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width + shift - _BITS_PER_WORD : 0;
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return (width >= _BITS_PER_WORD) ? ~0UL << shift
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: ((1UL << width) - 1) << shift;
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}
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void _set(addr_t index, addr_t width, bool free)
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{
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_check_range(index, width);
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addr_t rest, word, mask;
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do {
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word = _word(index);
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mask = _mask(index, width, rest);
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if (free) {
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if ((_words[word] & mask) != mask)
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throw Invalid_clear();
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_words[word] &= ~mask;
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} else {
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if (_words[word] & mask)
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throw Invalid_set();
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_words[word] |= mask;
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}
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index = (_word(index) + 1) * _BITS_PER_WORD;
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width = rest;
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} while (rest);
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}
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public:
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Bit_array_base(unsigned bits, addr_t *addr, bool clear)
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: _bit_cnt(bits),
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_word_cnt(_bit_cnt / _BITS_PER_WORD),
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_words(addr)
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{
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if (!bits || bits % _BITS_PER_WORD) throw Invalid_bit_count();
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if (clear) memset(_words, 0, sizeof(addr_t)*_word_cnt);
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}
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/**
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* Return true if at least one bit is set between
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* index until index + width - 1
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*/
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bool get(addr_t index, addr_t width) const
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{
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_check_range(index, width);
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bool used = false;
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addr_t rest, mask;
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do {
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mask = _mask(index, width, rest);
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used = _words[_word(index)] & mask;
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index = (_word(index) + 1) * _BITS_PER_WORD;
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width = rest;
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} while (!used && rest);
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return used;
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}
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void set(addr_t const index, addr_t const width) {
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_set(index, width, false); }
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void clear(addr_t const index, addr_t const width) {
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_set(index, width, true); }
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};
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template <unsigned BITS>
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class Bit_array : public Bit_array_base
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{
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private:
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static constexpr size_t _WORDS = BITS / _BITS_PER_WORD;
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static_assert(BITS % _BITS_PER_WORD == 0,
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"Count of bits need to be word aligned!");
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addr_t _array[_WORDS];
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public:
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Bit_array() : Bit_array_base(BITS, _array, true) { }
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};
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}
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#endif /* _INCLUDE__UTIL__BIT_ARRAY_H_ */
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