Chris@16: /////////////////////////////////////////////////////////////////////////////
Chris@16: //
Chris@16: // (C) Copyright Ion Gaztanaga  2007-2013
Chris@16: //
Chris@16: // Distributed under the Boost Software License, Version 1.0.
Chris@16: //    (See accompanying file LICENSE_1_0.txt or copy at
Chris@16: //          http://www.boost.org/LICENSE_1_0.txt)
Chris@16: //
Chris@16: // See http://www.boost.org/libs/intrusive for documentation.
Chris@16: //
Chris@16: /////////////////////////////////////////////////////////////////////////////
Chris@16: 
Chris@16: #ifndef BOOST_INTRUSIVE_POINTER_PLUS_BITS_HPP
Chris@16: #define BOOST_INTRUSIVE_POINTER_PLUS_BITS_HPP
Chris@16: 
Chris@101: #include <boost/intrusive/detail/config_begin.hpp>
Chris@101: #include <boost/intrusive/intrusive_fwd.hpp>
Chris@16: #include <boost/intrusive/detail/mpl.hpp> //ls_zeros
Chris@16: #include <boost/intrusive/detail/assert.hpp> //BOOST_INTRUSIVE_INVARIANT_ASSERT
Chris@16: 
Chris@101: #if defined(BOOST_HAS_PRAGMA_ONCE)
Chris@101: #  pragma once
Chris@101: #endif
Chris@101: 
Chris@16: namespace boost {
Chris@16: namespace intrusive {
Chris@16: 
Chris@16: //!This trait class is used to know if a pointer
Chris@16: //!can embed extra bits of information if
Chris@16: //!it's going to be used to point to objects
Chris@16: //!with an alignment of "Alignment" bytes.
Chris@16: template<class VoidPointer, std::size_t Alignment>
Chris@16: struct max_pointer_plus_bits
Chris@16: {
Chris@16:    static const std::size_t value = 0;
Chris@16: };
Chris@16: 
Chris@16: //!This is a specialization for raw pointers.
Chris@16: //!Raw pointers can embed extra bits in the lower bits
Chris@16: //!if the alignment is multiple of 2pow(NumBits).
Chris@16: template<std::size_t Alignment>
Chris@16: struct max_pointer_plus_bits<void*, Alignment>
Chris@16: {
Chris@16:    static const std::size_t value = detail::ls_zeros<Alignment>::value;
Chris@16: };
Chris@16: 
Chris@16: //!This is class that is supposed to have static methods
Chris@16: //!to embed extra bits of information in a pointer.
Chris@16: //!This is a declaration and there is no default implementation,
Chris@16: //!because operations to embed the bits change with every pointer type.
Chris@16: //!
Chris@16: //!An implementation that detects that a pointer type whose
Chris@16: //!has_pointer_plus_bits<>::value is non-zero can make use of these
Chris@16: //!operations to embed the bits in the pointer.
Chris@16: template<class Pointer, std::size_t NumBits>
Chris@16: struct pointer_plus_bits
Chris@16:    #ifdef BOOST_INTRUSIVE_DOXYGEN_INVOKED
Chris@16:    {}
Chris@16:    #endif
Chris@16: ;
Chris@16: 
Chris@16: //!This is the specialization to embed extra bits of information
Chris@16: //!in a raw pointer. The extra bits are stored in the lower bits of the pointer.
Chris@16: template<class T, std::size_t NumBits>
Chris@16: struct pointer_plus_bits<T*, NumBits>
Chris@16: {
Chris@16:    static const std::size_t Mask = ((std::size_t(1u) << NumBits) - 1);
Chris@16:    typedef T*        pointer;
Chris@16: 
Chris@16:    static pointer get_pointer(pointer n)
Chris@16:    {  return pointer(std::size_t(n) & ~Mask);  }
Chris@16: 
Chris@16:    static void set_pointer(pointer &n, pointer p)
Chris@16:    {
Chris@16:       BOOST_INTRUSIVE_INVARIANT_ASSERT(0 == (std::size_t(p) & Mask));
Chris@16:       n = pointer(std::size_t(p) | (std::size_t(n) & Mask));
Chris@16:    }
Chris@16: 
Chris@16:    static std::size_t get_bits(pointer n)
Chris@16:    {  return (std::size_t(n) & Mask);  }
Chris@16: 
Chris@16:    static void set_bits(pointer &n, std::size_t c)
Chris@16:    {
Chris@16:       BOOST_INTRUSIVE_INVARIANT_ASSERT(c <= Mask);
Chris@16:       n = pointer(std::size_t(get_pointer(n)) | c);
Chris@16:    }
Chris@16: };
Chris@16: 
Chris@16: } //namespace intrusive
Chris@16: } //namespace boost
Chris@16: 
Chris@101: #include <boost/intrusive/detail/config_end.hpp>
Chris@101: 
Chris@16: #endif //BOOST_INTRUSIVE_POINTER_PLUS_BITS_HPP