1 /* Copyright (c) 2015-2022. 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
10 #include "xbt/base.h" // XBT_ATTRIB_DEPRECATED_v334
19 template<class T, class U> class Extension;
20 template<class T> class Extendable;
22 template<class T, class U>
24 static constexpr std::size_t INVALID_ID = std::numeric_limits<std::size_t>::max();
25 std::size_t id_ = INVALID_ID;
26 friend class Extendable<T>;
27 explicit constexpr Extension(std::size_t id) : id_(id) {}
29 explicit constexpr Extension() = default;
30 std::size_t id() const { return id_; }
31 bool valid() const { return id_ != INVALID_ID; }
34 /** An Extendable is an object that you can extend with external elements.
36 * 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.
38 * Imagine that you want to write a plugin dealing with the energy in SimGrid.
39 * You will have to store some information about each and every host.
41 * You could modify the Host class directly (but your code will soon become messy).
42 * You could create a class EnergyHost deriving Host, but it is not easily combinable
43 * with a notion of Host extended with another concept (such as mobility).
44 * You could completely externalize these data with an associative map Host->EnergyHost.
45 * It would work, provided that you implement this classical feature correctly (and it would induce a little performance penalty).
46 * Instead, you should add a new extension to the Host class, that happens to be Extendable.
52 static std::vector<std::function<void(void*)>> deleters_;
53 std::vector<void*> extensions_{deleters_.size(), nullptr};
56 static size_t extension_create(const std::function<void(void*)>& deleter)
58 deleters_.emplace_back(deleter);
59 return deleters_.size() - 1;
61 template <class U> static Extension<T, U> extension_create(const std::function<void(void*)>& deleter)
63 return Extension<T,U>(extension_create(deleter));
65 template<class U> static
66 Extension<T,U> extension_create()
68 return Extension<T, U>(extension_create([](void* p) { delete static_cast<U*>(p); }));
70 Extendable() = default;
71 Extendable(const Extendable&) = delete;
72 Extendable& operator=(const Extendable&) = delete;
75 /* Call destructors in reverse order of their registrations
77 * The rationale for this, is that if an extension B as been added after
78 * an extension A, the subsystem of B might depend on the subsystem on A and
79 * an extension of B might need to have the extension of A around when executing
80 * its cleanup function/destructor. */
81 for (std::size_t i = extensions_.size(); i > 1; --i) // rank=0 is the spot of user's void*
82 if (extensions_[i - 1] != nullptr && deleters_[i - 1])
83 deleters_[i - 1](extensions_[i - 1]);
86 // Type-unsafe versions of the facet access methods:
87 void* extension(std::size_t rank) const
89 return rank < extensions_.size() ? extensions_[rank] : nullptr;
91 void extension_set(std::size_t rank, void* value, bool use_dtor = true)
93 if (rank >= extensions_.size())
94 extensions_.resize(rank + 1, nullptr);
95 void* old_value = this->extension(rank);
96 extensions_[rank] = value;
97 if (use_dtor && old_value != nullptr && deleters_[rank])
98 deleters_[rank](old_value);
101 // Type safe versions of the facet access methods:
102 template <class U> U* extension(Extension<T, U> rank) const { return static_cast<U*>(extension(rank.id())); }
104 void extension_set(Extension<T,U> rank, U* value, bool use_dtor = true)
106 extension_set(rank.id(), value, use_dtor);
108 // void* version, for C users and nostalgics
109 void set_data(void* data){
112 template <typename D> D* get_data() const { return static_cast<D*>(extensions_[0]); }
113 XBT_ATTRIB_DEPRECATED_v334("Please use typed template Extendable::get_data<>()") void* get_data() const
115 return get_data<void>();
117 // Convenience extension access when the type has an associated EXTENSION ID:
118 template <class U> U* extension() const { return extension<U>(U::EXTENSION_ID); }
119 template<class U> void extension_set(U* p) { extension_set<U>(U::EXTENSION_ID, p); }
122 // Initialized with a first element, to save space for void* user data
123 template <class T> std::vector<std::function<void(void*)>> Extendable<T>::deleters_{1};