blob: 10b2fe0eb933cbb7d1c060523bcf0613a9926aaf (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
|
/////////////////////////////////////////////////////////////////////////////
//
// (C) Copyright Ion Gaztanaga 2007-2009
//
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//
// See http://www.boost.org/libs/intrusive for documentation.
//
/////////////////////////////////////////////////////////////////////////////
#ifndef BOOST_INTRUSIVE_POINTER_PLUS_BITS_HPP
#define BOOST_INTRUSIVE_POINTER_PLUS_BITS_HPP
#include <boost/intrusive/detail/mpl.hpp> //ls_zeros
#include <boost/intrusive/detail/assert.hpp> //BOOST_INTRUSIVE_INVARIANT_ASSERT
namespace boost {
namespace intrusive {
//!This trait class is used to know if a pointer
//!can embed extra bits of information if
//!it's going to be used to point to objects
//!with an alignment of "Alignment" bytes.
template<class VoidPointer, std::size_t Alignment>
struct max_pointer_plus_bits
{
static const std::size_t value = 0;
};
//!This is a specialization for raw pointers.
//!Raw pointers can embed extra bits in the lower bits
//!if the alignment is multiple of 2pow(NumBits).
template<std::size_t Alignment>
struct max_pointer_plus_bits<void*, Alignment>
{
static const std::size_t value = detail::ls_zeros<Alignment>::value;
};
//!This is class that is supposed to have static methods
//!to embed extra bits of information in a pointer.
//!This is a declaration and there is no default implementation,
//!because operations to embed the bits change with every pointer type.
//!
//!An implementation that detects that a pointer type whose
//!has_pointer_plus_bits<>::value is non-zero can make use of these
//!operations to embed the bits in the pointer.
template<class Pointer, std::size_t NumBits>
struct pointer_plus_bits;
//!This is the specialization to embed extra bits of information
//!in a raw pointer. The extra bits are stored in the lower bits of the pointer.
template<class T, std::size_t NumBits>
struct pointer_plus_bits<T*, NumBits>
{
static const std::size_t Mask = ((std::size_t(1u) << NumBits) - 1);
typedef T* pointer;
static pointer get_pointer(pointer n)
{ return pointer(std::size_t(n) & ~Mask); }
static void set_pointer(pointer &n, pointer p)
{
BOOST_INTRUSIVE_INVARIANT_ASSERT(0 == (std::size_t(p) & Mask));
n = pointer(std::size_t(p) | (std::size_t(n) & Mask));
}
static std::size_t get_bits(pointer n)
{ return (std::size_t(n) & Mask); }
static void set_bits(pointer &n, std::size_t c)
{
BOOST_INTRUSIVE_INVARIANT_ASSERT(c <= Mask);
n = pointer(std::size_t(get_pointer(n)) | c);
}
};
} //namespace intrusive
} //namespace boost
#endif //BOOST_INTRUSIVE_POINTER_PLUS_BITS_HPP
|
