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Copyright (C) 2005 Free Software Foundation, Inc.
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This file is part of GNU Wget.
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GNU Wget is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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GNU Wget is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with Wget; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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In addition, as a special exception, the Free Software Foundation
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gives permission to link the code of its release of Wget with the
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OpenSSL project's "OpenSSL" library (or with modified versions of it
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that use the same license as the "OpenSSL" library), and distribute
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the linked executables. You must obey the GNU General Public License
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in all respects for all of the code used other than "OpenSSL". If you
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modify this file, you may extend this exception to your version of the
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file, but you are not obligated to do so. If you do not wish to do
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so, delete this exception statement from your version. */
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/* This file implements "portable timers" (ptimers), objects that
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measure elapsed time using the primitives most appropriate for the
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underlying operating system. The entry points are:
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ptimer_new -- creates a timer.
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ptimer_reset -- resets the timer's elapsed time to zero.
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ptimer_measure -- measure and return the time elapsed since
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creation or last reset.
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ptimer_read -- reads the last measured elapsed value.
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ptimer_destroy -- destroy the timer.
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ptimer_granularity -- returns the approximate granularity of the timers.
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Timers measure time in milliseconds, but the timings they return
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are floating point numbers, so they can carry as much precision as
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the underlying system timer supports. For example, to measure the
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time it takes to run a loop, you can use something like:
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ptimer *tmr = ptimer_new ();
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double msecs = ptimer_measure ();
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printf ("The loop took %.2f ms\n", msecs); */
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#else /* not HAVE_STRING_H */
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#endif /* not HAVE_STRING_H */
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#include <sys/types.h>
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/* Cygwin currently (as of 2005-04-08, Cygwin 1.5.14) lacks clock_getres,
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but still defines _POSIX_TIMERS! Because of that we simply use the
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Windows timers under Cygwin. */
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/* Depending on the OS and availability of gettimeofday(), one and
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only one of PTIMER_POSIX, PTIMER_GETTIMEOFDAY, PTIMER_WINDOWS, or
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PTIMER_TIME will be defined. */
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#undef PTIMER_GETTIMEOFDAY
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#if defined(WINDOWS) || defined(__CYGWIN__)
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# define PTIMER_WINDOWS /* use Windows timers */
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# if _POSIX_TIMERS - 0 > 0
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# define PTIMER_POSIX /* use POSIX timers (clock_gettime) */
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# ifdef HAVE_GETTIMEOFDAY
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# define PTIMER_GETTIMEOFDAY /* use gettimeofday */
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/* Elapsed time measurement using POSIX timers: system time is held in
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struct timespec, time is retrieved using clock_gettime, and
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resolution using clock_getres.
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This method is used on Unix systems that implement POSIX
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typedef struct timespec ptimer_system_time;
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#define IMPL_init posix_init
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#define IMPL_measure posix_measure
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#define IMPL_diff posix_diff
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#define IMPL_resolution posix_resolution
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/* clock_id to use for POSIX clocks. This tries to use
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CLOCK_MONOTONIC where available, CLOCK_REALTIME otherwise. */
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static int posix_clock_id;
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/* Resolution of the clock, in milliseconds. */
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static double posix_millisec_resolution;
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/* Decide which clock_id to use. */
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/* List of clocks we want to support: some systems support monotonic
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clocks, Solaris has "high resolution" clock (sometimes
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unavailable except to superuser), and all should support the
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#define NO_SYSCONF_CHECK -1
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static const struct {
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#if defined(_POSIX_MONOTONIC_CLOCK) && _POSIX_MONOTONIC_CLOCK - 0 >= 0
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{ CLOCK_MONOTONIC, _SC_MONOTONIC_CLOCK },
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{ CLOCK_HIGHRES, NO_SYSCONF_CHECK },
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{ CLOCK_REALTIME, NO_SYSCONF_CHECK },
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/* Determine the clock we can use. For a clock to be usable, it
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must be confirmed with sysconf (where applicable) and with
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clock_getres. If no clock is found, CLOCK_REALTIME is used. */
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for (i = 0; i < countof (clocks); i++)
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if (clocks[i].sysconf_name != NO_SYSCONF_CHECK)
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if (sysconf (clocks[i].sysconf_name) < 0)
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continue; /* sysconf claims this clock is unavailable */
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if (clock_getres (clocks[i].id, &r) < 0)
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continue; /* clock_getres doesn't work for this clock */
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posix_clock_id = clocks[i].id;
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posix_millisec_resolution = r.tv_sec * 1000.0 + r.tv_nsec / 1000000.0;
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/* Guard against broken clock_getres returning nonsensical
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if (posix_millisec_resolution == 0)
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posix_millisec_resolution = 1;
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if (i == countof (clocks))
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/* If no clock was found, it means that clock_getres failed for
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the realtime clock. */
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logprintf (LOG_NOTQUIET, _("Cannot get REALTIME clock frequency: %s\n"),
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/* Use CLOCK_REALTIME, but invent a plausible resolution. */
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posix_clock_id = CLOCK_REALTIME;
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posix_millisec_resolution = 1;
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posix_measure (ptimer_system_time *pst)
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clock_gettime (posix_clock_id, pst);
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posix_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
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return ((pst1->tv_sec - pst2->tv_sec) * 1000.0
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+ (pst1->tv_nsec - pst2->tv_nsec) / 1000000.0);
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posix_resolution (void)
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return posix_millisec_resolution;
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#endif /* PTIMER_POSIX */
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#ifdef PTIMER_GETTIMEOFDAY
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/* Elapsed time measurement using gettimeofday: system time is held in
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struct timeval, retrieved using gettimeofday, and resolution is
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This method is used Unix systems without POSIX timers. */
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typedef struct timeval ptimer_system_time;
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#define IMPL_measure gettimeofday_measure
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#define IMPL_diff gettimeofday_diff
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#define IMPL_resolution gettimeofday_resolution
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gettimeofday_measure (ptimer_system_time *pst)
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gettimeofday (pst, NULL);
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gettimeofday_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
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return ((pst1->tv_sec - pst2->tv_sec) * 1000.0
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+ (pst1->tv_usec - pst2->tv_usec) / 1000.0);
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gettimeofday_resolution (void)
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/* Granularity of gettimeofday varies wildly between architectures.
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However, it appears that on modern machines it tends to be better
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than 1ms. Assume 100 usecs. */
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#endif /* PTIMER_GETTIMEOFDAY */
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/* Elapsed time measurement using the time(2) call: system time is
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held in time_t, retrieved using time, and resolution is 1 second.
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This method is a catch-all for non-Windows systems without
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gettimeofday -- e.g. DOS or really old or non-standard Unix
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typedef time_t ptimer_system_time;
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#define IMPL_measure time_measure
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#define IMPL_diff time_diff
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#define IMPL_resolution time_resolution
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time_measure (ptimer_system_time *pst)
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time_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
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return 1000.0 * (*pst1 - *pst2);
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time_resolution (void)
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#endif /* PTIMER_TIME */
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#ifdef PTIMER_WINDOWS
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/* Elapsed time measurement on Windows: where high-resolution timers
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are available, time is stored in a LARGE_INTEGER and retrieved
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using QueryPerformanceCounter. Otherwise, it is stored in a DWORD
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and retrieved using GetTickCount.
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This method is used on Windows. */
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DWORD lores; /* In case GetTickCount is used */
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LARGE_INTEGER hires; /* In case high-resolution timer is used */
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} ptimer_system_time;
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#define IMPL_init windows_init
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#define IMPL_measure windows_measure
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#define IMPL_diff windows_diff
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#define IMPL_resolution windows_resolution
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/* Whether high-resolution timers are used. Set by ptimer_initialize_once
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the first time ptimer_new is called. */
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static int windows_hires_timers;
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/* Frequency of high-resolution timers -- number of updates per
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millisecond. Calculated the first time ptimer_new is called
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provided that high-resolution timers are available. */
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static double windows_hires_msfreq;
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QueryPerformanceFrequency (&freq);
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if (freq.QuadPart != 0)
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windows_hires_timers = 1;
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windows_hires_msfreq = (double) freq.QuadPart / 1000.0;
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windows_measure (ptimer_system_time *pst)
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if (windows_hires_timers)
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QueryPerformanceCounter (&pst->hires);
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/* Where hires counters are not available, use GetTickCount rather
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GetSystemTime, because it is unaffected by clock skew and
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simpler to use. Note that overflows don't affect us because we
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never use absolute values of the ticker, only the
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pst->lores = GetTickCount ();
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windows_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
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if (windows_hires_timers)
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return (pst1->hires.QuadPart - pst2->hires.QuadPart) / windows_hires_msfreq;
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return pst1->lores - pst2->lores;
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windows_resolution (void)
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if (windows_hires_timers)
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return 1.0 / windows_hires_msfreq;
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return 10; /* according to MSDN */
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#endif /* PTIMER_WINDOWS */
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/* The code below this point is independent of timer implementation. */
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/* The starting point in time which, subtracted from the current
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time, yields elapsed time. */
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ptimer_system_time start;
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/* The most recent elapsed time, calculated by ptimer_measure().
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Measured in milliseconds. */
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/* Approximately, the time elapsed between the true start of the
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measurement and the time represented by START. This is used for
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adjustment when clock skew is detected. */
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double elapsed_pre_start;
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/* Allocate a new timer and reset it. Return the new timer. */
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struct ptimer *pt = xnew0 (struct ptimer);
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static int init_done;
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/* Free the resources associated with the timer. Its further use is
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ptimer_destroy (struct ptimer *pt)
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/* Reset timer PT. This establishes the starting point from which
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ptimer_read() will return the number of elapsed milliseconds.
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It is allowed to reset a previously used timer. */
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ptimer_reset (struct ptimer *pt)
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/* Set the start time to the current time. */
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IMPL_measure (&pt->start);
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pt->elapsed_last = 0;
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pt->elapsed_pre_start = 0;
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/* Measure the elapsed time since timer creation/reset and return it
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to the caller. The value remains stored for further reads by
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This function causes the timer to call gettimeofday (or time(),
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etc.) to update its idea of current time. To get the elapsed
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interval in milliseconds, use ptimer_read.
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This function handles clock skew, i.e. time that moves backwards is
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ptimer_measure (struct ptimer *pt)
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ptimer_system_time now;
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elapsed = pt->elapsed_pre_start + IMPL_diff (&now, &pt->start);
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/* Ideally we'd just return the difference between NOW and
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pt->start. However, the system timer can be set back, and we
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could return a value smaller than when we were last called, even
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a negative value. Both of these would confuse the callers, which
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expect us to return monotonically nondecreasing values.
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Therefore: if ELAPSED is smaller than its previous known value,
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we reset pt->start to the current time and effectively start
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measuring from this point. But since we don't want the elapsed
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value to start from zero, we set elapsed_pre_start to the last
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elapsed time and increment all future calculations by that
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This cannot happen with Windows and POSIX monotonic/highres
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timers, but the check is not expensive. */
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if (elapsed < pt->elapsed_last)
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pt->elapsed_pre_start = pt->elapsed_last;
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elapsed = pt->elapsed_last;
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pt->elapsed_last = elapsed;
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/* Return the elapsed time in milliseconds between the last call to
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ptimer_reset and the last call to ptimer_update. */
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ptimer_read (const struct ptimer *pt)
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return pt->elapsed_last;
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/* Return the assessed resolution of the timer implementation, in
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milliseconds. This is used by code that tries to substitute a
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better value for timers that have returned zero. */
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ptimer_resolution (void)
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return IMPL_resolution ();
added
removed
src/ptimer.c
