1 /* Copyright (c) 2015-2023. The SimGrid Team.
2 * All rights reserved. */
4 /* This program is free software; you can redistribute it and/or modify it
5 * under the terms of the license (GNU LGPL) which comes with this package. */
7 #ifndef SIMGRID_XBT_LIB_HPP
8 #define SIMGRID_XBT_LIB_HPP
16 namespace simgrid::xbt {
18 template<class T, class U> class Extension;
19 template<class T> class Extendable;
21 template<class T, class U>
23 static constexpr std::size_t INVALID_ID = std::numeric_limits<std::size_t>::max();
24 std::size_t id_ = INVALID_ID;
25 friend class Extendable<T>;
26 explicit constexpr Extension(std::size_t id) : id_(id) {}
28 explicit constexpr Extension() = default;
29 std::size_t id() const { return id_; }
30 bool valid() const { return id_ != INVALID_ID; }
33 /** An Extendable is an object that you can extend with external elements.
35 * An Extension is one dimension of such extension. They are similar to the concept of mixins, that is, a set of behavior that is injected into a class without derivation.
37 * Imagine that you want to write a plugin dealing with the energy in SimGrid.
38 * You will have to store some information about each and every host.
40 * You could modify the Host class directly (but your code will soon become messy).
41 * You could create a class EnergyHost deriving Host, but it is not easily combinable
42 * with a notion of Host extended with another concept (such as mobility).
43 * You could completely externalize these data with an associative map Host->EnergyHost.
44 * It would work, provided that you implement this classical feature correctly (and it would induce a little performance penalty).
45 * Instead, you should add a new extension to the Host class, that happens to be Extendable.
51 static std::vector<std::function<void(void*)>> deleters_;
52 std::vector<void*> extensions_{deleters_.size(), nullptr};
55 static size_t extension_create(const std::function<void(void*)>& deleter)
57 deleters_.emplace_back(deleter);
58 return deleters_.size() - 1;
60 template <class U> static Extension<T, U> extension_create(const std::function<void(void*)>& deleter)
62 return Extension<T,U>(extension_create(deleter));
64 template<class U> static
65 Extension<T,U> extension_create()
67 return Extension<T, U>(extension_create([](void* p) { delete static_cast<U*>(p); }));
69 Extendable() = default;
70 Extendable(const Extendable&) = delete;
71 Extendable& operator=(const Extendable&) = delete;
74 /* Call destructors in reverse order of their registrations
76 * The rationale for this, is that if an extension B as been added after
77 * an extension A, the subsystem of B might depend on the subsystem on A and
78 * an extension of B might need to have the extension of A around when executing
79 * its cleanup function/destructor. */
80 for (std::size_t i = extensions_.size(); i > 1; --i) // rank=0 is the spot of user's void*
81 if (extensions_[i - 1] != nullptr && deleters_[i - 1])
82 deleters_[i - 1](extensions_[i - 1]);
85 // Type-unsafe versions of the facet access methods:
86 void* extension(std::size_t rank) const
88 return rank < extensions_.size() ? extensions_[rank] : nullptr;
90 void extension_set(std::size_t rank, void* value, bool use_dtor = true)
92 if (rank >= extensions_.size())
93 extensions_.resize(rank + 1, nullptr);
94 void* old_value = this->extension(rank);
95 extensions_[rank] = value;
96 if (use_dtor && old_value != nullptr && deleters_[rank])
97 deleters_[rank](old_value);
100 // Type safe versions of the facet access methods:
101 template <class U> U* extension(Extension<T, U> rank) const { return static_cast<U*>(extension(rank.id())); }
103 void extension_set(Extension<T,U> rank, U* value, bool use_dtor = true)
105 extension_set(rank.id(), value, use_dtor);
107 // void* version, for C users and nostalgics
108 void set_data(void* data){
111 template <typename D> D* get_data() const { return static_cast<D*>(extensions_[0]); }
112 template <typename D> std::unique_ptr<D> get_unique_data() { return std::unique_ptr<D>(get_data<D>()); }
114 // Convenience extension access when the type has an associated EXTENSION ID:
115 template <class U> U* extension() const { return extension<U>(U::EXTENSION_ID); }
116 template<class U> void extension_set(U* p) { extension_set<U>(U::EXTENSION_ID, p); }
119 // Initialized with a first element, to save space for void* user data
120 template <class T> std::vector<std::function<void(void*)>> Extendable<T>::deleters_{1};
121 } // namespace simgrid::xbt