bitwise_cast.hpp 2.0 KB

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  1. /*
  2. * Distributed under the Boost Software License, Version 1.0.
  3. * (See accompanying file LICENSE_1_0.txt or copy at
  4. * http://www.boost.org/LICENSE_1_0.txt)
  5. *
  6. * Copyright (c) 2009 Helge Bahmann
  7. * Copyright (c) 2012 Tim Blechmann
  8. * Copyright (c) 2013 - 2018 Andrey Semashev
  9. */
  10. /*!
  11. * \file atomic/detail/bitwise_cast.hpp
  12. *
  13. * This header defines \c bitwise_cast used to convert between storage and value types
  14. */
  15. #ifndef BOOST_ATOMIC_DETAIL_BITWISE_CAST_HPP_INCLUDED_
  16. #define BOOST_ATOMIC_DETAIL_BITWISE_CAST_HPP_INCLUDED_
  17. #include <cstddef>
  18. #include <boost/atomic/detail/config.hpp>
  19. #include <boost/atomic/detail/addressof.hpp>
  20. #include <boost/atomic/detail/string_ops.hpp>
  21. #include <boost/atomic/detail/type_traits/integral_constant.hpp>
  22. #ifdef BOOST_HAS_PRAGMA_ONCE
  23. #pragma once
  24. #endif
  25. namespace boost {
  26. namespace atomics {
  27. namespace detail {
  28. template< std::size_t FromSize, typename To >
  29. BOOST_FORCEINLINE void clear_padding(To& to, atomics::detail::true_type) BOOST_NOEXCEPT
  30. {
  31. BOOST_ATOMIC_DETAIL_MEMSET(reinterpret_cast< unsigned char* >(atomics::detail::addressof(to)) + FromSize, 0, sizeof(To) - FromSize);
  32. }
  33. template< std::size_t FromSize, typename To >
  34. BOOST_FORCEINLINE void clear_padding(To&, atomics::detail::false_type) BOOST_NOEXCEPT
  35. {
  36. }
  37. template< typename To, std::size_t FromSize, typename From >
  38. BOOST_FORCEINLINE To bitwise_cast(From const& from) BOOST_NOEXCEPT
  39. {
  40. To to;
  41. BOOST_ATOMIC_DETAIL_MEMCPY
  42. (
  43. atomics::detail::addressof(to),
  44. atomics::detail::addressof(from),
  45. (FromSize < sizeof(To) ? FromSize : sizeof(To))
  46. );
  47. atomics::detail::clear_padding< FromSize >(to, atomics::detail::integral_constant< bool, FromSize < sizeof(To) >());
  48. return to;
  49. }
  50. template< typename To, typename From >
  51. BOOST_FORCEINLINE To bitwise_cast(From const& from) BOOST_NOEXCEPT
  52. {
  53. return atomics::detail::bitwise_cast< To, sizeof(From) >(from);
  54. }
  55. } // namespace detail
  56. } // namespace atomics
  57. } // namespace boost
  58. #endif // BOOST_ATOMIC_DETAIL_BITWISE_CAST_HPP_INCLUDED_