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90d6f8bf62
libglim is an Apache-licensed C++ wrapper for lmdb, and rather than rolling our own it seems prudent to use it. Note: lmdb is not included in it, and unless something happens as did with libunbound, should be installed via each OS' package manager or equivalent.
40 lines
1.1 KiB
C++
40 lines
1.1 KiB
C++
#ifndef _GLIM_CHANNEL_INCLUDED
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#define _GLIM_CHANNEL_INCLUDED
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#include <atomic>
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#include <mutex>
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#include <thread>
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namespace glim {
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/// Unbuffered channel.
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/// Optimized for a single value (busy-waits on a second one).
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template <typename V>
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struct Channel {
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V _v;
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std::mutex _mutex; // Locked when there is no value.
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std::atomic_int_fast8_t _state; enum State {EMPTY = 0, WRITING = 1, FULL = 2};
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Channel(): _state (EMPTY) {_mutex.lock();}
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// Waits until the Channel is empty then stores the value.
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template <typename VA> void send (VA&& v) {
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for (;;) {
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int_fast8_t expectEmpty = EMPTY; if (_state.compare_exchange_weak (expectEmpty, WRITING)) break;
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std::this_thread::sleep_for (std::chrono::milliseconds (20));
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}
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try {_v = std::forward<V> (v);} catch (...) {_state = EMPTY; throw;}
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_state = FULL;
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_mutex.unlock(); // Allows the reader to proceed.
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}
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// Waits untill there is a value to receive.
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V receive() {
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_mutex.lock(); // Wait.
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V tmp = std::move (_v);
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assert (_state == FULL);
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_state = EMPTY;
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return tmp;
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}
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};
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} // namespace glim
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#endif
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