blob: 5cef8a65460f5196b76a12739e8099cb835b9d7a (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
|
#ifndef INCLUDED_SRC_BUILDTOOL_MULTITHREADING_ATOMIC_VALUE_HPP
#define INCLUDED_SRC_BUILDTOOL_MULTITHREADING_ATOMIC_VALUE_HPP
#include <atomic>
#include <functional>
#include <optional>
#include "src/utils/cpp/atomic.hpp"
// Value that can be set and get atomically. Reset is not thread-safe.
template <class T>
class AtomicValue {
public:
AtomicValue() noexcept = default;
AtomicValue(AtomicValue const& other) noexcept = delete;
AtomicValue(AtomicValue&& other) noexcept : data_{other.data_.load()} {}
~AtomicValue() noexcept = default;
auto operator=(AtomicValue const& other) noexcept = delete;
auto operator=(AtomicValue&& other) noexcept = delete;
// Atomically set value once and return its reference. If this method is
// called multiple times concurrently, the setter is called only once. In
// any case, this method blocks until the value is ready.
[[nodiscard]] auto SetOnceAndGet(
std::function<T()> const& setter) const& noexcept -> T const& {
if (data_.load() == nullptr) {
if (not load_.exchange(true)) {
data_.store(std::make_shared<T>(setter()));
data_.notify_all();
}
else {
data_.wait(nullptr);
}
}
return *data_.load();
}
[[nodiscard]] auto SetOnceAndGet(std::function<T()> const& setter) && =
delete;
// Reset, not thread-safe!
void Reset() noexcept {
load_ = false;
data_ = nullptr;
}
private:
mutable std::atomic<bool> load_{false};
mutable atomic_shared_ptr<T> data_{nullptr};
};
#endif // INCLUDED_SRC_BUILDTOOL_MULTITHREADING_ATOMIC_VALUE_HPP
|
