doublecheckedinit.hxx

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#ifndef INCLUDED_COMPHELPER_DOUBLECHECKEDINIT_HXX
#define INCLUDED_COMPHELPER_DOUBLECHECKEDINIT_HXX
 
#include <osl/getglobalmutex.hxx>
 
#include <atomic>
// HACK: <atomic> includes <stdbool.h>, which in some Clang versions does '#define bool bool',
// which confuses clang plugins.
#undef bool
#include <functional>
 
namespace comphelper
{
template <typename Type, typename Function = std::function<Type*()>,
          typename Guard = osl::MutexGuard, typename GuardCtor = osl::GetGlobalMutex>
static inline Type* doubleCheckedInit(std::atomic<Type*>& pointer, Function function,
                                      GuardCtor guardCtor = osl::GetGlobalMutex())
{
    Type* p = pointer.load(std::memory_order_acquire);
    if (!p)
    {
        Guard guard(guardCtor());
        p = pointer.load(std::memory_order_relaxed);
        if (!p)
        {
            p = function();
            pointer.store(p, std::memory_order_release);
        }
    }
    return p;
}
 
} // namespace
 
#endif // INCLUDED_COMPHELPER_DOUBLECHECKEDINIT_HXX
 
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