nix-super/src/libutil/monitor-fd.hh

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#pragma once
#include <thread>
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#include <atomic>
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#include <cstdlib>
#include <poll.h>
#include <sys/types.h>
#include <unistd.h>
#include <signal.h>
namespace nix {
class MonitorFdHup
{
private:
std::thread thread;
public:
MonitorFdHup(int fd)
{
thread = std::thread([fd]() {
while (true) {
/* Wait indefinitely until a POLLHUP occurs. */
struct pollfd fds[1];
fds[0].fd = fd;
/* This shouldn't be necessary, but macOS doesn't seem to
like a zeroed out events field.
See rdar://37537852.
*/
fds[0].events = POLLHUP;
auto count = poll(fds, 1, -1);
if (count == -1) abort(); // can't happen
/* This shouldn't happen, but can on macOS due to a bug.
See rdar://37550628.
This may eventually need a delay or further
coordination with the main thread if spinning proves
too harmful.
*/
if (count == 0) continue;
assert(fds[0].revents & POLLHUP);
triggerInterrupt();
break;
}
});
};
~MonitorFdHup()
{
pthread_cancel(thread.native_handle());
thread.join();
}
};
}