kopia lustrzana https://github.com/OpenRTX/OpenRTX
92 wiersze
4.3 KiB
C++
92 wiersze
4.3 KiB
C++
/***************************************************************************
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* Copyright (C) 2017 by Terraneo Federico *
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* *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License as published by *
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* the Free Software Foundation; either version 2 of the License, or *
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* (at your option) any later version. *
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* *
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* This program is distributed in the hope that it will be useful, *
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* but WITHOUT ANY WARRANTY; without even the implied warranty of *
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
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* GNU General Public License for more details. *
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* *
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* As a special exception, if other files instantiate templates or use *
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* macros or inline functions from this file, or you compile this file *
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* and link it with other works to produce a work based on this file, *
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* this file does not by itself cause the resulting work to be covered *
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* by the GNU General Public License. However the source code for this *
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* file must still be made available in accordance with the GNU General *
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* Public License. This exception does not invalidate any other reasons *
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* why a work based on this file might be covered by the GNU General *
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* Public License. *
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* *
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* You should have received a copy of the GNU General Public License *
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* along with this program; if not, see <http://www.gnu.org/licenses/> *
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***************************************************************************/
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#pragma once
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#include <tuple>
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namespace miosix {
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/**
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* \internal
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* Template-independent code of unmember is here to reduce code size.
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* Do not call this function directly
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* \param mixedField either the function pointer for nonvirtual functions,
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* or the vtable offset (with 1 added to disambiguate it from the previous case)
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* for virtual functions
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* \param thisOffset the offset to add to this for multiple/virtual inheritance
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* \param o the object pointer that has to be passed as this
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* \retun the ordinary function pointer and void * to call it with
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*/
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std::tuple<void (*)(void*), void*> unmemberLogic(unsigned long mixedField,
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long thisOffset, unsigned long *o) noexcept;
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/**
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* This function performs the forbidden cast of C++: casting from a member
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* function pointer of any class and a class pointer to an ordinary function
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* pointer and an opaque void * parameter to call it with. It allows to call
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* any member function of any class (that takes no parameters and returns void)
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* in an uniform and efficient way.
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*
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* The code is not portable, as the underlying representation of member function
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* pointers is not specified by the standard. According to
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* https://www.codeproject.com/Articles/7150/Member-Function-Pointers-and-the-Fastest-Possible
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* there are multiple implementations.
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* This code has been tested with the GCC and the LLVM compilers, in both
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* X86, X86-64 and ARM32.
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*
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* \param mfn a member function pointer of any class that takes no parameters
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* and returns void
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* \param object an object on which the member function has to be called
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* \return the ordinary function pointer and void * to call it with
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*/
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template<typename T>
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std::tuple<void (*)(void*), void*> unmember(void (T::*mfn)(), T *object) noexcept
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{
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//This code only works with GCC/LLVM
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#if !defined(__clang__) && !defined(__GNUC__)
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#error Unknown member function pointer layout
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#endif
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//A union is used to "inspect" the internals of the member function pointer
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union {
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void (T::*mfn)();
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struct {
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unsigned long mixedField;
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long thisOffset;
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};
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} unpack;
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unpack.mfn=mfn;
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//Unsigned long is used as its size is 4 on 32bit systems and 8 in 64bit
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unsigned long *o=reinterpret_cast<unsigned long*>(object);
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return unmemberLogic(unpack.mixedField,unpack.thisOffset,o);
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}
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} //namespace miosix
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