xapian-core/common/realtime.h

   1 /** @file
   2  *  @brief Functions for handling a time or time interval in a double.
   3  */
   4 /* Copyright (C) 2010,2011,2013,2014,2015,2020 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 #ifndef PACKAGE
  25 # error config.h must be included first in each C++ source file
  26 #endif
  27
  28 #include <cerrno>
  29 #include <cmath>
  30 #include <ctime>
  31
  32 #ifndef __WIN32__
  33 # ifdef HAVE_FTIME
  34 #  include <sys/timeb.h>
  35 # endif
  36 # ifdef HAVE_GETTIMEOFDAY
  37 #  include <sys/time.h>
  38 # endif
  39 # include "safesysselect.h"
  40 #else
  41 # include <sys/types.h>
  42 # include <sys/timeb.h>
  43 extern void xapian_sleep_milliseconds(unsigned int millisecs);
  44 #endif
  45
  46 namespace RealTime {
  47
  48 /// Return the current time.
  49 inline double now() {
  50 #if defined HAVE_CLOCK_GETTIME
  51     // We prefer functions which can return the time with a higher precision.
  52     // On POSIX platforms that means we prefer clock_gettime() over
  53     // gettimeofday() over ftime().
  54     //
  55     // (Also, POSIX.1-2008 stopped specifying ftime(), and marked gettimeofday()
  56     // as obsolete, recommending clock_gettime() instead.)
  57     //
  58     // Modern mingw provides clock_gettime().  For older mingw and MSVC we fall
  59     // back to _ftime64().
  60     struct timespec ts;
  61     if (usual(clock_gettime(CLOCK_REALTIME, &ts) == 0))
  62         return ts.tv_sec + (ts.tv_nsec * 1e-9);
  63     return double(std::time(NULL));
  64 #elif !defined __WIN32__
  65 # if defined HAVE_GETTIMEOFDAY
  66     struct timeval tv;
  67     if (usual(gettimeofday(&tv, NULL) == 0))
  68         return tv.tv_sec + (tv.tv_usec * 1e-6);
  69     return double(std::time(NULL));
  70 # elif defined HAVE_FTIME
  71     struct timeb tp;
  72 #  ifdef FTIME_RETURNS_VOID
  73     ftime(&tp);
  74 #  else
  75     if (rare(ftime(&tp) != 0))
  76         return double(std::time(NULL));
  77 #  endif
  78     return tp.time + (tp.millitm * 1e-3);
  79 # else
  80     return double(std::time(NULL));
  81 # endif
  82 #else
  83     // For __WIN32__.
  84     struct __timeb64 tp;
  85     _ftime64(&tp);
  86     return tp.time + tp.millitm * 1e-3;
  87 #endif
  88 }
  89
  90 /** Return the end time for a timeout in @a timeout seconds.
  91  *
  92  *  If @a timeout is 0, that means "no timeout", so 0 is returned.  Otherwise
  93  *  the current time plus @a timeout seconds is returned.
  94  */
  95 inline double end_time(double timeout) {
  96     return (timeout == 0.0 ? timeout : timeout + now());
  97 }
  98
  99 #if defined HAVE_NANOSLEEP || defined HAVE_TIMER_CREATE
 100 /// Fill in struct timespec from number of seconds in a double.
 101 inline void to_timespec(double t, struct timespec *ts) {
 102     double secs;
 103     ts->tv_nsec = long(std::modf(t, &secs) * 1e9);
 104     ts->tv_sec = long(secs);
 105 }
 106 #endif
 107
 108 /// Fill in struct timeval from number of seconds in a double.
 109 #ifndef __WIN32__
 110 inline void to_timeval(double t, struct timeval *tv) {
 111     double secs;
 112     tv->tv_usec = long(std::modf(t, &secs) * 1e6);
 113     tv->tv_sec = long(secs);
 114 }
 115 #else
 116 // Use a macro to avoid having to pull in winsock2.h just for struct timeval.
 117 # define to_timeval(T, TV) to_timeval_((T), (TV)->tv_sec, (TV)->tv_usec)
 118
 119 inline void to_timeval_(double t, long & tv_sec, long & tv_usec) {
 120     double secs;
 121     tv_usec = long(std::modf(t, &secs) * 1e6);
 122     tv_sec = long(secs);
 123 }
 124 #endif
 125
 126 /// Sleep until the time represented by this object.
 127 inline void sleep(double t) {
 128 #ifdef HAVE_NANOSLEEP
 129     // Available on modern POSIX systems and under modern mingw.
 130     double delta = t - RealTime::now();
 131     if (delta <= 0.0)
 132         return;
 133     struct timespec ts;
 134     to_timespec(delta, &ts);
 135     while (nanosleep(&ts, &ts) < 0 && errno == EINTR) { }
 136 #elif !defined __WIN32__
 137     double delta;
 138     struct timeval tv;
 139     do {
 140         delta = t - RealTime::now();
 141         if (delta <= 0.0)
 142             return;
 143         to_timeval(delta, &tv);
 144     } while (select(0, NULL, NULL, NULL, &tv) < 0 &&
 145              (errno == EINTR || errno == EAGAIN));
 146 #else
 147     double delta = t - RealTime::now();
 148     if (delta <= 0.0)
 149         return;
 150     while (rare(delta > 4294967.0)) {
 151         xapian_sleep_milliseconds(4294967000u);
 152         delta -= 4294967.0;
 153     }
 154     xapian_sleep_milliseconds(unsigned(delta * 1000.0));
 155 #endif
 156 }
 157
 158 }
 159
 160 #endif // XAPIAN_INCLUDED_REALTIME_H