blob: 385d154103cf0da04f014edbd85bc5cb8b15998f (
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
|
// file : build/map-key -*- C++ -*-
// copyright : Copyright (c) 2014-2015 Code Synthesis Ltd
// license : MIT; see accompanying LICENSE file
#ifndef BUILD_MAP_KEY
#define BUILD_MAP_KEY
#include <utility> // declval()
#include <functional> // hash
namespace build
{
// Google the "Emulating Boost.MultiIndex with Standard Containers" blog
// post for deatils.
//
template <typename T>
struct map_key
{
mutable const T* p;
map_key (const T* v = 0): p (v) {}
bool operator< (const map_key& x) const {return *p < *x.p;}
bool operator== (const map_key& x) const {return *p == *x.p;}
};
template <typename I>
struct map_iterator_adapter: I
{
typedef const typename I::value_type::second_type value_type;
typedef value_type* pointer;
typedef value_type& reference;
map_iterator_adapter () {}
map_iterator_adapter (I i): I (i) {}
map_iterator_adapter&
operator= (I i) {static_cast<I&> (*this) = i; return *this;}
reference operator* () const {return I::operator* ().second;}
pointer operator-> () const {return &I::operator-> ()->second;}
};
}
namespace std
{
template <typename T>
struct hash<build::map_key<T>>: hash<T>
{
size_t
operator() (build::map_key<T> x) const
noexcept (noexcept (declval<hash<T>> () (*x.p)))
{
return hash<T>::operator() (*x.p);
}
};
}
#endif // BUILD_MAP_KEY
|
