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xymopen/linux_magic.cpp

Created October 17, 2017 14:00
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C++ equivalences of the famous offset_of and container_of(owner_of) macro from Linux kernel
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linux_magic.cpp
template< class T, class M >
static inline constexpr ptrdiff_t offset_of( const M T::*member ) {
return reinterpret_cast< ptrdiff_t >( &( reinterpret_cast< T* >( 0 )->*member ) );
}
template< class T, class M >
static inline constexpr T* owner_of( M *ptr, const M T::*member ) {
return reinterpret_cast< T* >( reinterpret_cast< intptr_t >( ptr ) - offset_of( member ) );
}
@SayanNS
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SayanNS commented Jul 26, 2021

Hi, could you please write an example of how to use these templates?

@xymopen
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xymopen commented Aug 1, 2021

@SayanNS Hi, I've upload the sketch using the snippet. You can see how it was used in the kenerl-list class. In general, this snippet is used to implement intrusive containers, where dynamic memory allocation is strongly discouraged, such as an OS kernel.

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