83 lines
1.6 KiB
C++
83 lines
1.6 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_ALLOCATOR_H_
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#define _INCLUDE__UTIL__BIT_ALLOCATOR_H_
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#include <util/bit_array.h>
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namespace Genode { template<unsigned> class Bit_allocator; }
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template<unsigned BITS>
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class Genode::Bit_allocator
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{
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protected:
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addr_t _next;
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Bit_array<BITS> _array;
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/**
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* Reserve consecutive number of bits
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*
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* \noapi
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*/
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void _reserve(addr_t bit_start, size_t const num)
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{
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if (!num) return;
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_array.set(bit_start, num);
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}
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public:
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class Out_of_indices : Exception {};
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Bit_allocator() : _next(0) { }
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addr_t alloc(size_t const num_log2 = 0)
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{
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addr_t const step = 1UL << num_log2;
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addr_t max = ~0UL;
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do {
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try {
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/* throws exception if array is accessed outside bounds */
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for (addr_t i = _next & ~(step - 1); i < max; i += step) {
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if (_array.get(i, step))
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continue;
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_array.set(i, step);
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_next = i + step;
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return i;
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}
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} catch (typename Bit_array<BITS>::Invalid_index_access) { }
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max = _next;
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_next = 0;
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} while (max != 0);
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throw Out_of_indices();
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}
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void free(addr_t const bit_start, size_t const num_log2 = 0)
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{
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_array.clear(bit_start, 1UL << num_log2);
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_next = bit_start;
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}
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};
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#endif /* _INCLUDE__UTIL__BIT_ALLOCATOR_H_ */
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