genode/repos/base/include/util/bit_allocator.h
Norman Feske eaac3cc1bd Revised API documentation
This patch curates the API documentation to become suitable for the
functional specificaton, which is partially generated from the header
files.
2015-04-09 16:04:46 +02:00

83 lines
1.6 KiB
C++

/*
* \brief Allocator using bitmaps
* \author Alexander Boettcher
* \author Stefan Kalkowski
* \date 2012-06-14
*/
/*
* Copyright (C) 2012-2013 Genode Labs GmbH
*
* This file is part of the Genode OS framework, which is distributed
* under the terms of the GNU General Public License version 2.
*/
#ifndef _INCLUDE__UTIL__BIT_ALLOCATOR_H_
#define _INCLUDE__UTIL__BIT_ALLOCATOR_H_
#include <util/bit_array.h>
namespace Genode { template<unsigned> class Bit_allocator; }
template<unsigned BITS>
class Genode::Bit_allocator
{
protected:
addr_t _next;
Bit_array<BITS> _array;
/**
* Reserve consecutive number of bits
*
* \noapi
*/
void _reserve(addr_t bit_start, size_t const num)
{
if (!num) return;
_array.set(bit_start, num);
}
public:
class Out_of_indices : Exception {};
Bit_allocator() : _next(0) { }
addr_t alloc(size_t const num_log2 = 0)
{
addr_t const step = 1UL << num_log2;
addr_t max = ~0UL;
do {
try {
/* throws exception if array is accessed outside bounds */
for (addr_t i = _next & ~(step - 1); i < max; i += step) {
if (_array.get(i, step))
continue;
_array.set(i, step);
_next = i + step;
return i;
}
} catch (typename Bit_array<BITS>::Invalid_index_access) { }
max = _next;
_next = 0;
} while (max != 0);
throw Out_of_indices();
}
void free(addr_t const bit_start, size_t const num_log2 = 0)
{
_array.clear(bit_start, 1UL << num_log2);
_next = bit_start;
}
};
#endif /* _INCLUDE__UTIL__BIT_ALLOCATOR_H_ */