ExternalVendorCode/genode
1
0
Fork 0
mirror of https://github.com/genodelabs/genode.git synced 2024-12-19 13:47:56 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

unmanaged singleton: allow private constructors

Browse Source 
Introduces a class Unmanaged_singleton_constructor that can be declared as
friend to be able to call unmanaged_singleton on classes with a private
constructor. Enables the appliance of the singleton pattern.

Ref #1625
This commit is contained in:
Martin Stein 2015-07-10 12:26:11 +02:00 committed by Norman Feske
parent ba18ab7225
commit c6f73d365a
1 changed files with 17 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
repos/base/src/base/include/unmanaged_singleton.h
View File

@ -42,6 +42,22 @@
*/
inline void * operator new(Genode::size_t, void * p) { return p; }
/**
* Helper class for the use of unmanaged_singleton with the singleton pattern
*
* If a class wants to make its constructor private to force the singleton
* pattern, it can declare this class as friend to be able to still use the
* unmanaged_singleton template.
*/
struct Unmanaged_singleton_constructor
{
/**
* Call the constructor of 'T' with arguments 'args' at 'dst'
*/
template <typename T, typename... ARGS>
static void call(char * const dst, ARGS... args) { new (dst) T(args...); }
};
/**
* Create a singleton object that isn't implicitly constructed or destructed
*
@ -66,7 +82,7 @@ static inline T * unmanaged_singleton(ARGS... args)
/* execute constructor on first call */
if (!object_constructed) {
object_constructed = true;
new (&object_space) T(args...);
Unmanaged_singleton_constructor::call<T>(object_space, args...);
}
return reinterpret_cast<T *>(object_space);
}