66 lines
1 KiB
C++
66 lines
1 KiB
C++
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#pragma once
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#include <atomic>
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#include <mutex>
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#include <thread>
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#include <cinttypes>
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// left_right based on
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// https://github.com/pramalhe/ConcurrencyFreaks/blob/master/papers/left-right-2014.pdf
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// see concurrencyfreaks.com
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namespace left_right {
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template <typename T>
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struct left_right {
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template <typename Func>
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void update(Func &&f)
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{
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std::lock_guard<std::mutex> lock(write_mutex);
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auto cur = current.load();
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auto next = (cur + 1) & 1;
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while (readers[next] != 0)
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std::this_thread::yield();
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f(data[next]);
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current = next;
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while (readers[cur] != 0)
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std::this_thread::yield();
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f(data[cur]);
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}
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T read()
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{
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auto cur = current.load();
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for (;;) {
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readers[cur] += 1;
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auto cur_ = current.load();
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if (cur_ == cur)
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break;
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readers[cur] -= 1;
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cur = cur_;
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}
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auto val = data[cur];
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readers[cur] -= 1;
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return val;
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}
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private:
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std::atomic_uint_fast8_t current;
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std::atomic_long readers[2];
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std::mutex write_mutex;
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T data[2] = {{}, {}};
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};
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}
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