xapian-core/common/realtime.h

   1 /** @file realtime.h
   2  *  @brief Functions for handling a time or time interval in a double.
   3  */
   4 /* Copyright (C) 2010,2011,2013,2014,2015 Olly Betts
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (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 USA
  19  */
  20
  21 #ifndef XAPIAN_INCLUDED_REALTIME_H
  22 #define XAPIAN_INCLUDED_REALTIME_H
  23
  24 #include <cerrno>
  25 #include <cmath>
  26 #include <ctime>
  27
  28 #ifndef __WIN32__
  29 # ifdef HAVE_FTIME
  30 #  include <sys/timeb.h>
  31 # endif
  32 # ifdef HAVE_GETTIMEOFDAY
  33 #  include <sys/time.h>
  34 # endif
  35 # include "safesysselect.h"
  36 #else
  37 # include <sys/types.h>
  38 # include <sys/timeb.h>
  39 extern void xapian_sleep_milliseconds(unsigned int millisecs);
  40 #endif
  41
  42 namespace RealTime {
  43
  44 /// Return the current time.
  45 inline double now() {
  46 #ifndef __WIN32__
  47     // We prefer clock_gettime() over gettimeofday() over ftime().  This order
  48     // favours functions which can return the time with a higher precision.
  49     //
  50     // Also, POSIX.1-2008 stopped specifying ftime(), and marked gettimeofday()
  51     // as obsolete, recommending clock_gettime() instead.
  52 # if defined HAVE_CLOCK_GETTIME
  53     struct timespec ts;
  54     if (usual(clock_gettime(CLOCK_REALTIME, &ts) == 0))
  55         return ts.tv_sec + (ts.tv_nsec * 1e-9);
  56     return double(std::time(NULL));
  57 # elif defined HAVE_GETTIMEOFDAY
  58     struct timeval tv;
  59     if (usual(gettimeofday(&tv, NULL) == 0))
  60         return tv.tv_sec + (tv.tv_usec * 1e-6);
  61     return double(std::time(NULL));
  62 # elif defined HAVE_FTIME
  63     struct timeb tp;
  64 #  ifdef FTIME_RETURNS_VOID
  65     ftime(&tp);
  66 #  else
  67     if (rare(ftime(&tp) != 0))
  68         return double(std::time(NULL));
  69 #  endif
  70     return tp.time + (tp.millitm * 1e-3);
  71 # else
  72     return double(std::time(NULL));
  73 # endif
  74 #else
  75     struct __timeb64 tp;
  76     _ftime64(&tp);
  77     return tp.time + tp.millitm * 1e-3;
  78 #endif
  79 }
  80
  81 /** Return the end time for a timeout in @a timeout seconds.
  82  *
  83  *  If @a timeout is 0, that means "no timeout", so 0 is returned.  Otherwise
  84  *  the current time plus @a timeout seconds is returned.
  85  */
  86 inline double end_time(double timeout) {
  87     return (timeout == 0.0 ? timeout : timeout + now());
  88 }
  89
  90 #ifndef __WIN32__
  91 # if defined HAVE_NANOSLEEP || defined HAVE_TIMER_CREATE
  92 /// Fill in struct timespec from number of seconds in a double.
  93 inline void to_timespec(double t, struct timespec *ts) {
  94     double secs;
  95     ts->tv_nsec = long(std::modf(t, &secs) * 1e9);
  96     ts->tv_sec = long(secs);
  97 }
  98 # endif
  99
 100 /// Fill in struct timeval from number of seconds in a double.
 101 inline void to_timeval(double t, struct timeval *tv) {
 102     double secs;
 103     tv->tv_usec = long(std::modf(t, &secs) * 1e6);
 104     tv->tv_sec = long(secs);
 105 }
 106 #else
 107 // Use a macro to avoid having to pull in winsock2.h just for struct timeval.
 108 #define to_timeval(T, TV) to_timeval_((T), (TV)->tv_sec, (TV)->tv_usec)
 109 inline void to_timeval_(double t, long & tv_sec, long & tv_usec) {
 110     double secs;
 111     tv_usec = long(std::modf(t, &secs) * 1e6);
 112     tv_sec = long(secs);
 113 }
 114 #endif
 115
 116 /// Sleep until the time represented by this object.
 117 inline void sleep(double t) {
 118 #ifndef __WIN32__
 119 # ifdef HAVE_NANOSLEEP
 120     double delta = t - RealTime::now();
 121     if (delta <= 0.0)
 122         return;
 123     struct timespec ts;
 124     to_timespec(delta, &ts);
 125     while (nanosleep(&ts, &ts) < 0 && errno == EINTR) { }
 126 # else
 127     double delta;
 128     struct timeval tv;
 129     do {
 130         delta = t - RealTime::now();
 131         if (delta <= 0.0)
 132             return;
 133         to_timeval(delta, &tv);
 134     } while (select(0, NULL, NULL, NULL, &tv) < 0 &&
 135              (errno == EINTR || errno == EAGAIN));
 136 # endif
 137 #else
 138     double delta = t - RealTime::now();
 139     if (delta <= 0.0)
 140         return;
 141     while (rare(delta > 4294967.0)) {
 142         xapian_sleep_milliseconds(4294967000u);
 143         delta -= 4294967.0;
 144     }
 145     xapian_sleep_milliseconds(unsigned(delta * 1000.0));
 146 #endif
 147 }
 148
 149 }
 150
 151 #endif // XAPIAN_INCLUDED_REALTIME_H