matchtimeout.h

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/* Copyright (C) 2013,2014,2015,2016,2017 Olly Betts
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see
 * <https://www.gnu.org/licenses/>.
 */
 
#ifndef XAPIAN_INCLUDED_MATCHTIMEOUT_H
#define XAPIAN_INCLUDED_MATCHTIMEOUT_H
 
#ifndef PACKAGE
# error config.h must be included first in each C++ source file
#endif
 
#ifdef HAVE_TIMER_CREATE
#include "realtime.h"
 
#include <signal.h>
#include <time.h>
#include "safeunistd.h" // For _POSIX_* feature test macros.
 
extern "C" {
 
static void
set_timeout_flag(union sigval sv)
{
    *(reinterpret_cast<volatile bool*>(sv.sival_ptr)) = true;
}
 
}
 
// The monotonic clock is the better basis for timeouts, but not always
// available.
 
#ifndef _POSIX_MONOTONIC_CLOCK
const clockid_t TIMEOUT_CLOCK = CLOCK_REALTIME;
#elif defined __sun
// Solaris defines CLOCK_MONOTONIC, but "man timer_create" doesn't mention it
// and when using it timer_create() fails with "EPERM" (perhaps you need to be
// root to use it?  I can't test that).
//
// Solaris defines _POSIX_MONOTONIC_CLOCK so we need to special case.
const clockid_t TIMEOUT_CLOCK = CLOCK_REALTIME;
#elif defined __CYGWIN__
// https://cygwin.com/cygwin-api/std-notes.html currently (2023-04-18) says:
//
//     clock_nanosleep currently supports only CLOCK_REALTIME and
//     CLOCK_MONOTONIC.  clock_setres, clock_settime, and timer_create
//     currently support only CLOCK_REALTIME.
//
// So CLOCK_MONOTONIC is defined, but not supported by timer_create().
const clockid_t TIMEOUT_CLOCK = CLOCK_REALTIME;
#else
const clockid_t TIMEOUT_CLOCK = CLOCK_MONOTONIC;
#endif
 
class TimeOut {
    struct sigevent sev;
    timer_t timerid;
    volatile bool expired = false;
 
    TimeOut(const TimeOut&) = delete;
 
    TimeOut& operator=(const TimeOut&) = delete;
 
  public:
    explicit TimeOut(double limit) {
        if (limit > 0) {
            sev.sigev_notify = SIGEV_THREAD;
            sev.sigev_notify_function = set_timeout_flag;
            sev.sigev_notify_attributes = NULL;
            sev.sigev_value.sival_ptr =
                static_cast<void*>(const_cast<bool*>(&expired));
            if (usual(timer_create(TIMEOUT_CLOCK, &sev, &timerid) == 0)) {
                struct itimerspec interval;
                interval.it_interval.tv_sec = 0;
                interval.it_interval.tv_nsec = 0;
                RealTime::to_timespec(limit, &interval.it_value);
                if (usual(timer_settime(timerid, 0, &interval, NULL) == 0)) {
                    // Timeout successfully set.
                    return;
                }
                timer_delete(timerid);
            }
        }
        sev.sigev_notify = SIGEV_NONE;
    }
 
    ~TimeOut() {
        if (sev.sigev_notify != SIGEV_NONE) {
            timer_delete(timerid);
            sev.sigev_notify = SIGEV_NONE;
        }
    }
 
    bool timed_out() const { return expired; }
};
#else
class TimeOut {
  public:
    explicit TimeOut(double) { }
    bool timed_out() const { return false; }
};
#endif
 
#endif // XAPIAN_INCLUDED_MATCHTIMEOUT_H