2 Copyright (C) 2005, 2006, 2007 Free Software Foundation, Inc.
4 This file is part of GNU Wget.
6 GNU Wget 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 3 of the License, or
9 (at your option) any later version.
11 GNU Wget 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.
16 You should have received a copy of the GNU General Public License
17 along with Wget. If not, see <http://www.gnu.org/licenses/>.
19 In addition, as a special exception, the Free Software Foundation
20 gives permission to link the code of its release of Wget with the
21 OpenSSL project's "OpenSSL" library (or with modified versions of it
22 that use the same license as the "OpenSSL" library), and distribute
23 the linked executables. You must obey the GNU General Public License
24 in all respects for all of the code used other than "OpenSSL". If you
25 modify this file, you may extend this exception to your version of the
26 file, but you are not obligated to do so. If you do not wish to do
27 so, delete this exception statement from your version. */
29 /* This file implements "portable timers" (ptimers), objects that
30 measure elapsed time using the primitives most appropriate for the
31 underlying operating system. The entry points are:
33 ptimer_new -- creates a timer.
34 ptimer_reset -- resets the timer's elapsed time to zero.
35 ptimer_measure -- measure and return the time elapsed since
36 creation or last reset.
37 ptimer_read -- reads the last measured elapsed value.
38 ptimer_destroy -- destroy the timer.
39 ptimer_granularity -- returns the approximate granularity of the timers.
41 Timers measure time in seconds, returning the timings as floating
42 point numbers, so they can carry as much precision as the
43 underlying system timer supports. For example, to measure the time
44 it takes to run a loop, you can use something like:
46 ptimer *tmr = ptimer_new ();
49 double secs = ptimer_measure ();
50 printf ("The loop took %.2fs\n", secs); */
62 #ifdef HAVE_SYS_TIME_H
63 # include <sys/time.h>
66 /* Cygwin currently (as of 2005-04-08, Cygwin 1.5.14) lacks clock_getres,
67 but still defines _POSIX_TIMERS! Because of that we simply use the
68 Windows timers under Cygwin. */
75 /* Depending on the OS, one and only one of PTIMER_POSIX,
76 PTIMER_GETTIMEOFDAY, or PTIMER_WINDOWS will be defined. */
79 #undef PTIMER_GETTIMEOFDAY
82 #if defined(WINDOWS) || defined(__CYGWIN__)
83 # define PTIMER_WINDOWS /* use Windows timers */
84 #elif _POSIX_TIMERS - 0 > 0
85 # define PTIMER_POSIX /* use POSIX timers (clock_gettime) */
87 # define PTIMER_GETTIMEOFDAY /* use gettimeofday */
91 /* Elapsed time measurement using POSIX timers: system time is held in
92 struct timespec, time is retrieved using clock_gettime, and
93 resolution using clock_getres.
95 This method is used on Unix systems that implement POSIX
98 typedef struct timespec ptimer_system_time;
100 #define IMPL_init posix_init
101 #define IMPL_measure posix_measure
102 #define IMPL_diff posix_diff
103 #define IMPL_resolution posix_resolution
105 /* clock_id to use for POSIX clocks. This tries to use
106 CLOCK_MONOTONIC where available, CLOCK_REALTIME otherwise. */
107 static int posix_clock_id;
109 /* Resolution of the clock, initialized in posix_init. */
110 static double posix_clock_resolution;
112 /* Decide which clock_id to use. */
117 /* List of clocks we want to support: some systems support monotonic
118 clocks, Solaris has "high resolution" clock (sometimes
119 unavailable except to superuser), and all should support the
121 #define NO_SYSCONF_CHECK -1
122 static const struct {
126 #if defined(_POSIX_MONOTONIC_CLOCK) && _POSIX_MONOTONIC_CLOCK - 0 >= 0
127 { CLOCK_MONOTONIC, _SC_MONOTONIC_CLOCK },
130 { CLOCK_HIGHRES, NO_SYSCONF_CHECK },
132 { CLOCK_REALTIME, NO_SYSCONF_CHECK },
136 /* Determine the clock we can use. For a clock to be usable, it
137 must be confirmed with sysconf (where applicable) and with
138 clock_getres. If no clock is found, CLOCK_REALTIME is used. */
140 for (i = 0; i < countof (clocks); i++)
143 if (clocks[i].sysconf_name != NO_SYSCONF_CHECK)
144 if (sysconf (clocks[i].sysconf_name) < 0)
145 continue; /* sysconf claims this clock is unavailable */
146 if (clock_getres (clocks[i].id, &r) < 0)
147 continue; /* clock_getres doesn't work for this clock */
148 posix_clock_id = clocks[i].id;
149 posix_clock_resolution = (double) r.tv_sec + r.tv_nsec / 1e9;
150 /* Guard against nonsense returned by a broken clock_getres. */
151 if (posix_clock_resolution == 0)
152 posix_clock_resolution = 1e-3;
155 if (i == countof (clocks))
157 /* If no clock was found, it means that clock_getres failed for
158 the realtime clock. */
159 logprintf (LOG_NOTQUIET, _("Cannot get REALTIME clock frequency: %s\n"),
161 /* Use CLOCK_REALTIME, but invent a plausible resolution. */
162 posix_clock_id = CLOCK_REALTIME;
163 posix_clock_resolution = 1e-3;
168 posix_measure (ptimer_system_time *pst)
170 clock_gettime (posix_clock_id, pst);
174 posix_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
176 return ((pst1->tv_sec - pst2->tv_sec)
177 + (pst1->tv_nsec - pst2->tv_nsec) / 1e9);
181 posix_resolution (void)
183 return posix_clock_resolution;
185 #endif /* PTIMER_POSIX */
187 #ifdef PTIMER_GETTIMEOFDAY
188 /* Elapsed time measurement using gettimeofday: system time is held in
189 struct timeval, retrieved using gettimeofday, and resolution is
192 This method is used Unix systems without POSIX timers. */
194 typedef struct timeval ptimer_system_time;
196 #define IMPL_measure gettimeofday_measure
197 #define IMPL_diff gettimeofday_diff
198 #define IMPL_resolution gettimeofday_resolution
201 gettimeofday_measure (ptimer_system_time *pst)
203 gettimeofday (pst, NULL);
207 gettimeofday_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
209 return ((pst1->tv_sec - pst2->tv_sec)
210 + (pst1->tv_usec - pst2->tv_usec) / 1e6);
214 gettimeofday_resolution (void)
216 /* Granularity of gettimeofday varies wildly between architectures.
217 However, it appears that on modern machines it tends to be better
218 than 1ms. Assume 100 usecs. */
221 #endif /* PTIMER_GETTIMEOFDAY */
223 #ifdef PTIMER_WINDOWS
224 /* Elapsed time measurement on Windows: where high-resolution timers
225 are available, time is stored in a LARGE_INTEGER and retrieved
226 using QueryPerformanceCounter. Otherwise, it is stored in a DWORD
227 and retrieved using GetTickCount.
229 This method is used on Windows. */
232 DWORD lores; /* In case GetTickCount is used */
233 LARGE_INTEGER hires; /* In case high-resolution timer is used */
234 } ptimer_system_time;
236 #define IMPL_init windows_init
237 #define IMPL_measure windows_measure
238 #define IMPL_diff windows_diff
239 #define IMPL_resolution windows_resolution
241 /* Whether high-resolution timers are used. Set by ptimer_initialize_once
242 the first time ptimer_new is called. */
243 static bool windows_hires_timers;
245 /* Frequency of high-resolution timers -- number of updates per
246 second. Calculated the first time ptimer_new is called provided
247 that high-resolution timers are available. */
248 static double windows_hires_freq;
255 QueryPerformanceFrequency (&freq);
256 if (freq.QuadPart != 0)
258 windows_hires_timers = true;
259 windows_hires_freq = (double) freq.QuadPart;
264 windows_measure (ptimer_system_time *pst)
266 if (windows_hires_timers)
267 QueryPerformanceCounter (&pst->hires);
269 /* Where hires counters are not available, use GetTickCount rather
270 GetSystemTime, because it is unaffected by clock skew and
271 simpler to use. Note that overflows don't affect us because we
272 never use absolute values of the ticker, only the
274 pst->lores = GetTickCount ();
278 windows_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
280 if (windows_hires_timers)
281 return (pst1->hires.QuadPart - pst2->hires.QuadPart) / windows_hires_freq;
283 return pst1->lores - pst2->lores;
287 windows_resolution (void)
289 if (windows_hires_timers)
290 return 1.0 / windows_hires_freq;
292 return 10; /* according to MSDN */
294 #endif /* PTIMER_WINDOWS */
296 /* The code below this point is independent of timer implementation. */
299 /* The starting point in time which, subtracted from the current
300 time, yields elapsed time. */
301 ptimer_system_time start;
303 /* The most recent elapsed time, calculated by ptimer_measure(). */
306 /* Approximately, the time elapsed between the true start of the
307 measurement and the time represented by START. This is used for
308 adjustment when clock skew is detected. */
309 double elapsed_pre_start;
312 /* Allocate a new timer and reset it. Return the new timer. */
317 struct ptimer *pt = xnew0 (struct ptimer);
319 static bool init_done;
330 /* Free the resources associated with the timer. Its further use is
334 ptimer_destroy (struct ptimer *pt)
339 /* Reset timer PT. This establishes the starting point from which
340 ptimer_measure() will return the elapsed time in seconds. It is
341 allowed to reset a previously used timer. */
344 ptimer_reset (struct ptimer *pt)
346 /* Set the start time to the current time. */
347 IMPL_measure (&pt->start);
348 pt->elapsed_last = 0;
349 pt->elapsed_pre_start = 0;
352 /* Measure the elapsed time since timer creation/reset. This causes
353 the timer to internally call clock_gettime (or gettimeofday, etc.)
354 to update its idea of current time. The time is returned, but is
355 also stored for later access through ptimer_read().
357 This function handles clock skew, i.e. time that moves backwards is
361 ptimer_measure (struct ptimer *pt)
363 ptimer_system_time now;
367 elapsed = pt->elapsed_pre_start + IMPL_diff (&now, &pt->start);
369 /* Ideally we'd just return the difference between NOW and
370 pt->start. However, the system timer can be set back, and we
371 could return a value smaller than when we were last called, even
372 a negative value. Both of these would confuse the callers, which
373 expect us to return monotonically nondecreasing values.
375 Therefore: if ELAPSED is smaller than its previous known value,
376 we reset pt->start to the current time and effectively start
377 measuring from this point. But since we don't want the elapsed
378 value to start from zero, we set elapsed_pre_start to the last
379 elapsed time and increment all future calculations by that
382 This cannot happen with Windows and POSIX monotonic/highres
383 timers, but the check is not expensive. */
385 if (elapsed < pt->elapsed_last)
388 pt->elapsed_pre_start = pt->elapsed_last;
389 elapsed = pt->elapsed_last;
392 pt->elapsed_last = elapsed;
396 /* Return the most recent elapsed time measured with ptimer_measure.
397 If ptimer_measure has not yet been called since the timer was
398 created or reset, this returns 0. */
401 ptimer_read (const struct ptimer *pt)
403 return pt->elapsed_last;
406 /* Return the assessed resolution of the timer implementation, in
407 seconds. This is used by code that tries to substitute a better
408 value for timers that have returned zero. */
411 ptimer_resolution (void)
413 return IMPL_resolution ();