1/////////////////////////////////////////////////////////////////////////////
2//
3// (C) Copyright Ion Gaztanaga 2007-2013
4//
5// Distributed under the Boost Software License, Version 1.0.
6// (See accompanying file LICENSE_1_0.txt or copy at
7// http://www.boost.org/LICENSE_1_0.txt)
8//
9// See http://www.boost.org/libs/intrusive for documentation.
10//
11/////////////////////////////////////////////////////////////////////////////
12
13#ifndef BOOST_INTRUSIVE_POINTER_PLUS_BITS_HPP
14#define BOOST_INTRUSIVE_POINTER_PLUS_BITS_HPP
15
16#include <boost/intrusive/detail/config_begin.hpp>
17#include <boost/intrusive/intrusive_fwd.hpp>
18#include <boost/intrusive/detail/mpl.hpp> //ls_zeros
19#include <boost/intrusive/detail/assert.hpp> //BOOST_INTRUSIVE_INVARIANT_ASSERT
20
21#if defined(BOOST_HAS_PRAGMA_ONCE)
22# pragma once
23#endif
24
25
26//GCC reports uninitialized values when an uninitialized pointer plus bits type
27//is asigned some bits or some pointer value, but that's ok, because we don't want
28//to default initialize parts that are not being updated.
29#if defined(BOOST_GCC)
30# if (BOOST_GCC >= 40600)
31# pragma GCC diagnostic push
32# pragma GCC diagnostic ignored "-Wuninitialized"
33# if (BOOST_GCC >= 40700)
34# pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
35# endif
36# endif
37#endif
38
39namespace boost {
40namespace intrusive {
41
42//!This trait class is used to know if a pointer
43//!can embed extra bits of information if
44//!it's going to be used to point to objects
45//!with an alignment of "Alignment" bytes.
46template<class VoidPointer, std::size_t Alignment>
47struct max_pointer_plus_bits
48{
49 static const std::size_t value = 0;
50};
51
52//!This is a specialization for raw pointers.
53//!Raw pointers can embed extra bits in the lower bits
54//!if the alignment is multiple of 2pow(NumBits).
55template<std::size_t Alignment>
56struct max_pointer_plus_bits<void*, Alignment>
57{
58 static const std::size_t value = detail::ls_zeros<Alignment>::value;
59};
60
61//!This is class that is supposed to have static methods
62//!to embed extra bits of information in a pointer.
63//!This is a declaration and there is no default implementation,
64//!because operations to embed the bits change with every pointer type.
65//!
66//!An implementation that detects that a pointer type whose
67//!has_pointer_plus_bits<>::value is non-zero can make use of these
68//!operations to embed the bits in the pointer.
69template<class Pointer, std::size_t NumBits>
70struct pointer_plus_bits
71 #ifdef BOOST_INTRUSIVE_DOXYGEN_INVOKED
72 {}
73 #endif
74;
75
76//!This is the specialization to embed extra bits of information
77//!in a raw pointer. The extra bits are stored in the lower bits of the pointer.
78template<class T, std::size_t NumBits>
79struct pointer_plus_bits<T*, NumBits>
80{
81 static const uintptr_t Mask = uintptr_t((uintptr_t(1u) << NumBits) - 1);
82 typedef T* pointer;
83
84 BOOST_INTRUSIVE_FORCEINLINE static pointer get_pointer(pointer n) BOOST_NOEXCEPT
85 { return pointer(uintptr_t(n) & uintptr_t(~Mask)); }
86
87 BOOST_INTRUSIVE_FORCEINLINE static void set_pointer(pointer &n, pointer p) BOOST_NOEXCEPT
88 {
89 BOOST_INTRUSIVE_INVARIANT_ASSERT(0 == (uintptr_t(p) & Mask));
90 n = pointer(uintptr_t(p) | (uintptr_t(n) & Mask));
91 }
92
93 BOOST_INTRUSIVE_FORCEINLINE static std::size_t get_bits(pointer n) BOOST_NOEXCEPT
94 { return std::size_t(uintptr_t(n) & Mask); }
95
96 BOOST_INTRUSIVE_FORCEINLINE static void set_bits(pointer &n, std::size_t c) BOOST_NOEXCEPT
97 {
98 BOOST_INTRUSIVE_INVARIANT_ASSERT(uintptr_t(c) <= Mask);
99 n = pointer(uintptr_t((get_pointer)(n)) | uintptr_t(c));
100 }
101};
102
103} //namespace intrusive
104} //namespace boost
105
106#if defined(BOOST_GCC) && (BOOST_GCC >= 40600)
107# pragma GCC diagnostic pop
108#endif
109
110#include <boost/intrusive/detail/config_end.hpp>
111
112#endif //BOOST_INTRUSIVE_POINTER_PLUS_BITS_HPP
113

source code of boost/libs/intrusive/include/boost/intrusive/pointer_plus_bits.hpp