xapian-core/matcher/matchtimeout.h

   1 /** @file matchtimeout.h
   2  * @brief Time limits for the matcher
   3  */
   4 /* Copyright (C) 2013,2014,2015,2016,2017 Olly Betts
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License as
   8  * published by the Free Software Foundation; either version 2 of the
   9  * License, or (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301
  19  * USA
  20  */
  21
  22 #ifndef XAPIAN_INCLUDED_MATCHTIMEOUT_H
  23 #define XAPIAN_INCLUDED_MATCHTIMEOUT_H
  24
  25 #ifdef HAVE_TIMER_CREATE
  26 #include "realtime.h"
  27
  28 #include <signal.h>
  29 #include <time.h>
  30 #include "safeunistd.h" // For _POSIX_* feature test macros.
  31
  32 extern "C" {
  33
  34 static void
  35 set_timeout_flag(union sigval sv)
  36 {
  37     *(reinterpret_cast<volatile bool*>(sv.sival_ptr)) = true;
  38 }
  39
  40 }
  41
  42 // The monotonic clock is the better basis for timeouts, but not always
  43 // available.
  44
  45 #ifndef _POSIX_MONOTONIC_CLOCK
  46 const clockid_t TIMEOUT_CLOCK = CLOCK_REALTIME;
  47 #elif defined __sun
  48 // Solaris defines CLOCK_MONOTONIC, but "man timer_create" doesn't mention it
  49 // and when using it timer_create() fails with "EPERM" (perhaps you need to be
  50 // root to use it?  I can't test that).
  51 //
  52 // Solaris defines _POSIX_MONOTONIC_CLOCK so we need to special case.
  53 const clockid_t TIMEOUT_CLOCK = CLOCK_REALTIME;
  54 #elif defined __CYGWIN__
  55 // https://cygwin.com/cygwin-api/std-notes.html currently (2016-05-13) says:
  56 //
  57 //     clock_nanosleep currently supports only CLOCK_REALTIME and
  58 //     CLOCK_MONOTONIC.  clock_setres, clock_settime, and timer_create
  59 //     currently support only CLOCK_REALTIME.
  60 //
  61 // So CLOCK_MONOTONIC is defined, but not supported by timer_create().
  62 const clockid_t TIMEOUT_CLOCK = CLOCK_REALTIME;
  63 #else
  64 const clockid_t TIMEOUT_CLOCK = CLOCK_MONOTONIC;
  65 #endif
  66
  67 class TimeOut {
  68     struct sigevent sev;
  69     timer_t timerid;
  70     volatile bool expired;
  71
  72     TimeOut(const TimeOut&) = delete;
  73
  74     TimeOut& operator=(const TimeOut&) = delete;
  75
  76   public:
  77     explicit TimeOut(double limit) : expired(false) {
  78         if (limit > 0) {
  79             sev.sigev_notify = SIGEV_THREAD;
  80             sev.sigev_notify_function = set_timeout_flag;
  81             sev.sigev_notify_attributes = NULL;
  82             sev.sigev_value.sival_ptr =
  83                 static_cast<void*>(const_cast<bool*>(&expired));
  84             if (usual(timer_create(TIMEOUT_CLOCK, &sev, &timerid) == 0)) {
  85                 struct itimerspec interval;
  86                 interval.it_interval.tv_sec = 0;
  87                 interval.it_interval.tv_nsec = 0;
  88                 RealTime::to_timespec(limit, &interval.it_value);
  89                 if (usual(timer_settime(timerid, 0, &interval, NULL) == 0)) {
  90                     // Timeout successfully set.
  91                     return;
  92                 }
  93                 timer_delete(timerid);
  94             }
  95         }
  96         sev.sigev_notify = SIGEV_NONE;
  97     }
  98
  99     ~TimeOut() {
 100         if (sev.sigev_notify != SIGEV_NONE) {
 101             timer_delete(timerid);
 102             sev.sigev_notify = SIGEV_NONE;
 103         }
 104     }
 105
 106     bool timed_out() const { return expired; }
 107 };
 108 #else
 109 class TimeOut {
 110   public:
 111     explicit TimeOut(double) { }
 112     bool timed_out() const { return false; }
 113 };
 114 #endif
 115
 116 #endif // XAPIAN_INCLUDED_MATCHTIMEOUT_H