// Copyright (c) 2014-2016, The Monero Project
//
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//
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// permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this list of
// conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice, this list
// of conditions and the following disclaimer in the documentation and/or other
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//
// 3. Neither the name of the copyright holder nor the names of its contributors may be
// used to endorse or promote products derived from this software without specific
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//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
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#pragma once
#include <boost/optional/optional.hpp>
#include <boost/thread/condition_variable.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/thread/thread.hpp>
#include <cstddef>
#include <functional>
#include <thread>
#include <utility>
#include <vector>
namespace tools
{
//! Manages zero or more threads for work dispatching.
class thread_group
{
public:
//! \return `get_max_concurrency() ? get_max_concurrency() - 1 : 0`
static std::size_t optimal();
//! \return `count ? min(count - 1, optimal()) : 0`
static std::size_t optimal_with_max(std::size_t count);
//! Create an optimal number of threads.
explicit thread_group() : thread_group(optimal()) {}
//! Create exactly `count` threads.
explicit thread_group(std::size_t count);
thread_group(thread_group const&) = delete;
thread_group(thread_group&&) = delete;
//! Joins threads, but does not necessarily run all dispatched functions.
~thread_group() = default;
thread_group& operator=(thread_group const&) = delete;
thread_group& operator=(thread_group&&) = delete;
//! \return Number of threads owned by `this` group.
std::size_t count() const noexcept {
if (internal) {
return internal->count();
}
return 0;
}
//! \return True iff a function was available and executed (on `this_thread`).
bool try_run_one() noexcept {
if (internal) {
return internal->try_run_one();
}
return false;
}
/*! `f` is invoked immediately if `count() == 0`, otherwise execution of `f`
is queued for next available thread. If `f` is queued, any exception leaving
that function will result in process termination. Use std::packaged_task if
exceptions need to be handled. */
template<typename F>
void dispatch(F&& f) {
if (internal) {
internal->dispatch(std::forward<F>(f));
}
else {
f();
}
}
private:
class data {
public:
data(std::size_t count);
~data() noexcept;
std::size_t count() const noexcept {
return threads.size();
}
bool try_run_one() noexcept;
void dispatch(std::function<void()> f);
private:
struct work;
struct node {
std::unique_ptr<work> ptr;
};
struct work {
std::function<void()> f;
node next;
};
//! Requires lock on `mutex`.
std::unique_ptr<work> get_next() noexcept;
//! Blocks until destructor is invoked, only call from thread.
void run() noexcept;
private:
std::vector<boost::thread> threads;
node head;
node* last;
boost::condition_variable has_work;
boost::mutex mutex;
bool stop;
};
private:
// optionally construct elements, without separate heap allocation
boost::optional<data> internal;
};
}
