67 lines
1.5 KiB
C++
67 lines
1.5 KiB
C++
/*
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* \brief Utility to ensure that a size value doesn't exceed a limit
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* \author Martin Stein
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* \date 2016-08-24
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*/
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/*
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* Copyright (C) 2016-2017 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 _NET__SIZE_GUARD_H_
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#define _NET__SIZE_GUARD_H_
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/* Genode includes */
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#include <base/stdint.h>
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#include <base/exception.h>
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namespace Net { class Size_guard; }
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class Net::Size_guard
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{
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public:
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struct Exceeded : Genode::Exception { };
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private:
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Genode::size_t const _total_size;
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Genode::size_t _head_size { 0 };
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Genode::size_t _tail_size { 0 };
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void _consume(Genode::size_t &s1,
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Genode::size_t &s2,
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Genode::size_t s1_consume)
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{
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Genode::size_t const new_s1 = s1 + s1_consume;
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if (new_s1 < s1 || new_s1 > _total_size - s2)
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throw Exceeded();
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s1 = new_s1;
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}
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public:
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Size_guard(Genode::size_t total_size) : _total_size { total_size } { }
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void consume_head(Genode::size_t size) { _consume(_head_size, _tail_size, size); }
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void consume_tail(Genode::size_t size) { _consume(_tail_size, _head_size, size); }
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/***************
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** Accessors **
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***************/
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Genode::size_t unconsumed() const { return _total_size - _head_size - _tail_size; }
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Genode::size_t tail_size() const { return _tail_size; }
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Genode::size_t head_size() const { return _head_size; }
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Genode::size_t total_size() const { return _total_size; }
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};
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#endif /* _NET__SIZE_GUARD_H_ */
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