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/*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#pragma once
#ifdef WITH_TBB
# include <tbb/enumerable_thread_specific.h>
#endif
#include <atomic>
#include <mutex>
#include "BLI_map.hh"
#include "BLI_utility_mixins.hh"
namespace blender::threading {
namespace enumerable_thread_specific_utils {
inline std::atomic<int> next_id = 0;
inline thread_local int thread_id = next_id.fetch_add(1, std::memory_order_relaxed);
} // namespace enumerable_thread_specific_utils
/**
* This is mainly a wrapper for `tbb::enumerable_thread_specific`. The wrapper is needed because we
* want to be able to build without tbb.
*
* More features of the tbb version can be wrapped when they are used.
*/
template<typename T> class EnumerableThreadSpecific : NonCopyable, NonMovable {
#ifdef WITH_TBB
private:
tbb::enumerable_thread_specific<T> values_;
public:
using iterator = typename tbb::enumerable_thread_specific<T>::iterator;
EnumerableThreadSpecific() = default;
template<typename F> EnumerableThreadSpecific(F initializer) : values_(std::move(initializer))
{
}
T &local()
{
return values_.local();
}
iterator begin()
{
return values_.begin();
}
iterator end()
{
return values_.end();
}
#else /* WITH_TBB */
private:
std::mutex mutex_;
/* Maps thread ids to their corresponding values. The values are not embedded in the map, so that
* their addresses do not change when the map grows. */
Map<int, std::reference_wrapper<T>> values_;
Vector<std::unique_ptr<T>> owned_values_;
std::function<void(void *)> initializer_;
public:
using iterator = typename Map<int, std::reference_wrapper<T>>::MutableValueIterator;
EnumerableThreadSpecific() : initializer_([](void *buffer) { new (buffer) T(); })
{
}
template<typename F>
EnumerableThreadSpecific(F initializer)
: initializer_([=](void *buffer) { new (buffer) T(initializer()); })
{
}
T &local()
{
const int thread_id = enumerable_thread_specific_utils::thread_id;
std::lock_guard lock{mutex_};
return values_.lookup_or_add_cb(thread_id, [&]() {
T *value = (T *)::operator new(sizeof(T));
initializer_(value);
owned_values_.append(std::unique_ptr<T>{value});
return std::reference_wrapper<T>{*value};
});
}
iterator begin()
{
return values_.values().begin();
}
iterator end()
{
return values_.values().end();
}
#endif /* WITH_TBB */
};
} // namespace blender::threading
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