nix-super/src/libutil/monitor-fd.hh
John Ericson ac89bb064a Split up util.{hh,cc}
All OS and IO operations should be moved out, leaving only some misc
portable pure functions.

This is useful to avoid copious CPP when doing things like Windows and
Emscripten ports.

Newly exposed functions to break cycles:

 - `restoreSignals`
 - `updateWindowSize`
2023-11-05 12:20:02 -05:00

72 lines
1.8 KiB
C++

#pragma once
///@file
#include <thread>
#include <atomic>
#include <cstdlib>
#include <poll.h>
#include <sys/types.h>
#include <unistd.h>
#include <signal.h>
#include "signals.hh"
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;
/* Polling for no specific events (i.e. just waiting
for an error/hangup) doesn't work on macOS
anymore. So wait for read events and ignore
them. */
fds[0].events =
#ifdef __APPLE__
POLLRDNORM
#else
0
#endif
;
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;
if (fds[0].revents & POLLHUP) {
triggerInterrupt();
break;
}
/* This will only happen on macOS. We sleep a bit to
avoid waking up too often if the client is sending
input. */
sleep(1);
}
});
};
~MonitorFdHup()
{
pthread_cancel(thread.native_handle());
thread.join();
}
};
}