boost的integer/integer_mask.hpp僅僅做了單個位的bit mask
要多個位必須寫很多遍high_bit_mask_t
使用low_bits_mask_t也不能完全解決問題
所以自己用Typelist的那種寫法寫了一個
用法舉例
bit_mask<INT_LIST_2(2, 3)>::value返回一個值，該值的第2、3位被置為1
其余位為0
1
2 namespace multi_bit_mask
3 {
4 namespace details
5 {
6
7 template <typename T>
8 struct get_size
9 {
10 enum {size = sizeof(T)};
11 };
12
13 template <int Bit>
14 struct bit_storage
15 {
16 typedef typename bit_storage<Bit - 1>::storage_type storage_type;
17 };
18
19 //---------platform dependency-----------------------
20
21 typedef unsigned int smallest_storage_type;
22 typedef unsigned long long largest_storage_type;
23
24
25
26 template <>
27 struct bit_storage<0>
28 {
29 typedef smallest_storage_type storage_type;
30 };
31
32 template <>
33 struct bit_storage<get_size<smallest_storage_type>::size * 8>
34 {
35 typedef largest_storage_type storage_type;
36 };
37
38 //disable the 65th bit
39 template <>
40 struct bit_storage<get_size<largest_storage_type>::size * 8>
41 {
42 typedef void storage_type;
43 };
44
45 //---------end of platform dependency----------------
46
47
48 template <unsigned int N, typename Next>
49 struct int_list
50 {
51 typedef typename bit_storage<N>::storage_type storage_type;
52 static const storage_type value = N;
53 typedef Next next;
54 };
55
56 struct null_type{};
57
58 template<typename T1, typename T2, bool is_first>
59 struct selector
60 {
61 typedef T1 type;
62 };
63
64 template<typename T1, typename T2>
65 struct compare_type
66 {
67 const static bool is_larger = sizeof(T1) > sizeof(T2);
68 typedef typename selector<T1, T2, is_larger>::type large_type;
69 typedef typename selector<T1, T2, !is_larger>::type small_type;
70 };
71
72
73
74 template<typename T1, typename T2>
75 struct selector<T1, T2, false>
76 {
77 typedef T2 type;
78 };
79
80 template <typename List>
81 class find_largest_storage
82 {
83 typedef typename find_largest_storage<typename List::next>::storage_type T1;
84 typedef typename bit_storage<List::value>::storage_type T2;
85 public:
86 typedef typename compare_type<T1, T2>::large_type storage_type;
87 };
88
89 template <>
90 class find_largest_storage<null_type>
91 {
92 public:
93 typedef smallest_storage_type storage_type;
94 };
95
96
97 }
98
99
100
101
102
103 template <int N>
104 struct single_bit_mask
105 {
106 typedef typename details::bit_storage<N>::storage_type storage_type;
107 static const storage_type value
108 = static_cast<storage_type>(single_bit_mask<N - 1>::value) * 2;
109 };
110
111 template <>
112 struct single_bit_mask<0>
113 {
114 typedef details::bit_storage<0>::storage_type storage_type;
115 static const storage_type value = 1;
116 };
117
118
119 typedef details::null_type null_type;
120
121 template <int N, typename Next>
122 struct int_list_t : public details::int_list<N, Next> {};
123
124 template <typename List>
125 struct bit_mask
126 {
127 public:
128
129 typedef typename details::find_largest_storage<List>::storage_type storage_type;
130
131 static const storage_type value
132 = static_cast<storage_type>(single_bit_mask<List::value>::value)
133 | static_cast<storage_type>(bit_mask<typename List::next>::value);
134 };
135
136 template <>
137 struct bit_mask<null_type>
138 {
139 typedef details::bit_storage<0>::storage_type storage_type;
140 static const storage_type value = 0;
141 };
142
143
144
145
146
147 #define INT_LIST_1(n1) multi_bit_mask::int_list_t<n1, multi_bit_mask::null_type>
148 #define INT_LIST_2(n1, n2) multi_bit_mask::int_list_t<n1, INT_LIST_1(n2) >
149 #define INT_LIST_3(n1, n2, n3) multi_bit_mask::int_list_t<n1, INT_LIST_2(n2, n3) >
150 #define INT_LIST_4(n1, n2, n3, n4) multi_bit_mask::int_list_t<n1, INT_LIST_3(n2, n3, n4) >
151 #define INT_LIST_5(n1, n2, n3, n4, n5) multi_bit_mask::int_list_t<n1, INT_LIST_4(n2, n3, n4, n5) >
152 #define INT_LIST_6(n1, n2, n3, n4, n5, n6) multi_bit_mask::int_list_t<n1, INT_LIST_5(n2, n3, n4, n5, n6) >
153 #define INT_LIST_7(n1, n2, n3, n4, n5, n6, n7) multi_bit_mask::int_list_t<n1, INT_LIST_6(n2, n3, n4, n5, n6, n7) >
154 #define INT_LIST_8(n1, n2, n3, n4, n5, n6, n7, n8) multi_bit_mask::int_list_t<n1, INT_LIST_7(n2, n3, n4, n5, n6, n7, n8) >
155
156 }
157
158
159
sample
#include < iostream >
#include " multi_bit_mask.h "
using namespace std;
int main()
{
cout << multi_bit_mask::bit_mask < INT_LIST_1( 1 ) > ::value << endl;
cout << multi_bit_mask::bit_mask < INT_LIST_5( 0 , 1 , 2 , 3 , 4 ) > ::value << endl;
cout << multi_bit_mask::bit_mask < INT_LIST_7( 0 , 1 , 2 , 3 , 4 , 4 , 2 ) > ::value << endl;
posted on 2006-10-26 23:37
shifan3 閱讀(1451)
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