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#pragma once
#include "sync.hh"
#include "util.hh"
#include <queue>
#include <functional>
#include <thread>
namespace nix {
/* A simple thread pool that executes a queue of work items
(lambdas). */
class ThreadPool
{
public:
ThreadPool(size_t nrThreads = 0);
// FIXME: use std::packaged_task?
typedef std::function<void()> work_t;
/* Enqueue a function to be executed by the thread pool. */
void enqueue(const work_t & t);
/* Execute work items until the queue is empty. Note that work
items are allowed to add new items to the queue; this is
handled correctly. Queue processing stops prematurely if any
work item throws an exception. This exception is propagated to
the calling thread. If multiple work items throw an exception
concurrently, only one item is propagated; the others are
printed on stderr and otherwise ignored. */
void process();
private:
size_t nrThreads;
struct State
{
std::queue<work_t> left;
size_t pending = 0;
std::exception_ptr exception;
};
Sync<State> state;
std::condition_variable wakeup;
};
}
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