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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#pragma once
#include "lazy.h"
#include "detached.h"
#include <coroutine>
#include <atomic>
namespace vespalib::coro {
// Tracks work that is being performed concurrently
class ActiveWork {
private:
std::atomic<uint32_t> _pending;
std::coroutine_handle<> _waiting;
template <typename T>
Detached signal_when_done(Lazy<T> &lazy) {
co_await lazy.done();
if (_pending.fetch_sub(1, std::memory_order_acq_rel) == 1) {
_waiting.resume();
}
}
struct join_awaiter {
ActiveWork &self;
join_awaiter(ActiveWork &self_in) noexcept : self(self_in) {}
constexpr bool await_ready() const noexcept { return false; }
constexpr void await_resume() const noexcept {}
bool await_suspend(std::coroutine_handle<> handle) noexcept __attribute__((noinline));
};
public:
ActiveWork() : _pending(1), _waiting(std::noop_coroutine()) {}
~ActiveWork();
template <typename T>
void start(Lazy<T> &lazy) {
_pending.fetch_add(1, std::memory_order_relaxed);
signal_when_done(lazy);
}
auto join() noexcept { return join_awaiter(*this); }
};
}
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