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120 lines
2.6 KiB
C++
120 lines
2.6 KiB
C++
/*
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* \brief Flexpage iterator
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* \author Alexander Boettcher
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* \date 2013-01-07
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*/
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/*
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* Copyright (C) 2013-2017 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 Affero General Public License version 3.
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*/
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#ifndef _INCLUDE__UTIL__FLEX_ITERATOR_H_
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#define _INCLUDE__UTIL__FLEX_ITERATOR_H_
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#include <base/stdint.h>
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#include <util/misc_math.h>
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namespace Genode {
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struct Flexpage;
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class Flexpage_iterator;
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}
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struct Genode::Flexpage
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{
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addr_t addr = ~0UL;
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addr_t hotspot = 0;
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size_t log2_order = 0;
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Flexpage() { }
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Flexpage(addr_t a, addr_t h, size_t o)
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: addr(a), hotspot(h), log2_order(o) { }
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bool valid() { return addr != ~0UL; }
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};
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class Genode::Flexpage_iterator
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{
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private:
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addr_t _src_start = 0, _src_size = 0;
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addr_t _dst_start = 0, _dst_size = 0;
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addr_t _hotspot = 0, _offset = 0;
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/**
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* Find least significant set bit in value
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*/
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inline addr_t
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lsb_bit(addr_t const scan)
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{
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if (scan == 0)
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return ~0UL;
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return __builtin_ctzl(scan);
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}
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public:
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Flexpage_iterator() { }
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Flexpage_iterator(addr_t src_start, size_t src_size,
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addr_t dst_start, size_t dst_size,
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addr_t hotspot)
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:
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_src_start(src_start), _src_size(src_size),
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_dst_start(dst_start), _dst_size(dst_size),
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_hotspot(hotspot), _offset(0)
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{ }
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Flexpage page()
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{
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size_t const size = min (_src_size, _dst_size);
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addr_t const from_end = _src_start + size;
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addr_t const to_end = _dst_start + size;
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if (_offset >= size)
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return Flexpage();
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addr_t const from_curr = _src_start + _offset;
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addr_t const to_curr = _dst_start + _offset;
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/*
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* The common alignment corresponds to the number of least
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* significant zero bits in both addresses.
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*/
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addr_t const common_bits = from_curr | to_curr;
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/* find least set bit in common bits */
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size_t order = lsb_bit(common_bits);
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size_t max = (order == ~0UL) ? ~0UL : (1UL << order);
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/* look if it still fits into both 'src' and 'dst' ranges */
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if ((from_end - from_curr) < max) {
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order = log2(from_end - from_curr);
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order = (order == ~0UL) ? 12 : order;
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max = 1UL << order;
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}
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if ((to_end - to_curr) < max) {
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order = log2(to_end - to_curr);
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order = (order == ~0UL) ? 12 : order;
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}
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if (order >= sizeof(_offset) * 8)
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return Flexpage();
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/* advance offset by current flexpage size */
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_offset += (1UL << order);
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return Flexpage(from_curr, _hotspot + _offset - (1UL << order), order);
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}
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};
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#endif /* _INCLUDE__UTIL__FLEX_ITERATOR_H_ */
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