forked from lix-project/lix
47 lines
1.1 KiB
C++
47 lines
1.1 KiB
C++
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#pragma once
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#include <future>
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#include <functional>
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namespace nix {
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/* A callback is a wrapper around a lambda that accepts a valid of
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type T or an exception. (We abuse std::future<T> to pass the value or
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exception.) */
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template<typename T>
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class Callback
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{
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std::function<void(std::future<T>)> fun;
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std::atomic_flag done = ATOMIC_FLAG_INIT;
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public:
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Callback(std::function<void(std::future<T>)> fun) : fun(fun) { }
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Callback(Callback && callback) : fun(std::move(callback.fun))
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{
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auto prev = callback.done.test_and_set();
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if (prev) done.test_and_set();
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}
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void operator()(T && t) noexcept
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{
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auto prev = done.test_and_set();
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assert(!prev);
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std::promise<T> promise;
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promise.set_value(std::move(t));
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fun(promise.get_future());
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}
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void rethrow(const std::exception_ptr & exc = std::current_exception()) noexcept
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{
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auto prev = done.test_and_set();
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assert(!prev);
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std::promise<T> promise;
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promise.set_exception(exc);
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fun(promise.get_future());
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}
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};
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}
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