2 Copyright (C) 2005 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 2 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, write to the Free Software
18 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
20 In addition, as a special exception, the Free Software Foundation
21 gives permission to link the code of its release of Wget with the
22 OpenSSL project's "OpenSSL" library (or with modified versions of it
23 that use the same license as the "OpenSSL" library), and distribute
24 the linked executables. You must obey the GNU General Public License
25 in all respects for all of the code used other than "OpenSSL". If you
26 modify this file, you may extend this exception to your version of the
27 file, but you are not obligated to do so. If you do not wish to do
28 so, delete this exception statement from your version. */
30 /* This file implements "portable timers" (ptimers), objects that
31 measure elapsed time using the primitives most appropriate for the
32 underlying operating system. The entry points are:
34 ptimer_new -- creates a timer.
35 ptimer_reset -- resets the timer's elapsed time to zero.
36 ptimer_measure -- measure and return the time elapsed since
37 creation or last reset.
38 ptimer_read -- reads the last measured elapsed value.
39 ptimer_destroy -- destroy the timer.
40 ptimer_granularity -- returns the approximate granularity of the timers.
42 Timers measure time in milliseconds, but the timings they return
43 are floating point numbers, so they can carry as much precision as
44 the underlying system timer supports. For example, to measure the
45 time it takes to run a loop, you can use something like:
47 ptimer *tmr = ptimer_new ();
50 double msecs = ptimer_measure ();
51 printf ("The loop took %.2f ms\n", msecs); */
59 #else /* not HAVE_STRING_H */
61 #endif /* not HAVE_STRING_H */
62 #include <sys/types.h>
76 /* Depending on the OS and availability of gettimeofday(), one and
77 only one of PTIMER_POSIX, PTIMER_GETTIMEOFDAY, PTIMER_WINDOWS, or
78 PTIMER_TIME will be defined. */
81 #undef PTIMER_GETTIMEOFDAY
86 # define PTIMER_WINDOWS /* use Windows timers */
88 # if _POSIX_TIMERS > 0
89 # define PTIMER_POSIX /* use POSIX timers (clock_gettime) */
91 # ifdef HAVE_GETTIMEOFDAY
92 # define PTIMER_GETTIMEOFDAY /* use gettimeofday */
100 /* Elapsed time measurement using POSIX timers: system time is held in
101 struct timespec, time is retrieved using clock_gettime, and
102 resolution using clock_getres.
104 This method is used on Unix systems that implement POSIX
107 typedef struct timespec ptimer_system_time;
109 #define IMPL_init posix_init
110 #define IMPL_measure posix_measure
111 #define IMPL_diff posix_diff
112 #define IMPL_resolution posix_resolution
114 /* clock_id to use for POSIX clocks. This tries to use
115 CLOCK_MONOTONIC where available, CLOCK_REALTIME otherwise. */
116 static int posix_clock_id;
118 /* Resolution of the clock, in milliseconds. */
119 static double posix_millisec_resolution;
121 /* Decide which clock_id to use. */
126 /* List of clocks we want to support: some systems support monotonic
127 clocks, Solaris has "high resolution" clock (sometimes
128 unavailable except to superuser), and all should support the
130 #define NO_SYSCONF_CHECK -1
131 static const struct {
135 #if defined(_POSIX_MONOTONIC_CLOCK) && _POSIX_MONOTONIC_CLOCK >= 0
136 { CLOCK_MONOTONIC, _SC_MONOTONIC_CLOCK },
139 { CLOCK_HIGHRES, NO_SYSCONF_CHECK },
141 { CLOCK_REALTIME, NO_SYSCONF_CHECK },
145 /* Determine the clock we can use. For a clock to be usable, it
146 must be confirmed with sysconf (where applicable) and with
147 clock_getres. If no clock is found, CLOCK_REALTIME is used. */
149 for (i = 0; i < countof (clocks); i++)
152 if (clocks[i].sysconf_name != NO_SYSCONF_CHECK)
153 if (sysconf (clocks[i].sysconf_name) < 0)
154 continue; /* sysconf claims this clock is unavailable */
155 if (clock_getres (clocks[i].id, &r) < 0)
156 continue; /* clock_getres doesn't work for this clock */
157 posix_clock_id = clocks[i].id;
158 posix_millisec_resolution = r.tv_sec * 1000.0 + r.tv_nsec / 1000000.0;
159 /* Guard against broken clock_getres returning nonsensical
161 if (posix_millisec_resolution == 0)
162 posix_millisec_resolution = 1;
165 if (i == countof (clocks))
167 /* If no clock was found, it means that clock_getres failed for
168 the realtime clock. */
169 logprintf (LOG_NOTQUIET, _("Cannot get REALTIME clock frequency: %s\n"),
171 /* Use CLOCK_REALTIME, but invent a plausible resolution. */
172 posix_clock_id = CLOCK_REALTIME;
173 posix_millisec_resolution = 1;
178 posix_measure (ptimer_system_time *pst)
180 clock_gettime (posix_clock_id, pst);
184 posix_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
186 return ((pst1->tv_sec - pst2->tv_sec) * 1000.0
187 + (pst1->tv_nsec - pst2->tv_nsec) / 1000000.0);
191 posix_resolution (void)
193 return posix_millisec_resolution;
195 #endif /* PTIMER_POSIX */
197 #ifdef PTIMER_GETTIMEOFDAY
198 /* Elapsed time measurement using gettimeofday: system time is held in
199 struct timeval, retrieved using gettimeofday, and resolution is
202 This method is used Unix systems without POSIX timers. */
204 typedef struct timeval ptimer_system_time;
206 #define IMPL_measure gettimeofday_measure
207 #define IMPL_diff gettimeofday_diff
208 #define IMPL_resolution gettimeofday_resolution
211 gettimeofday_measure (ptimer_system_time *pst)
213 gettimeofday (pst, NULL);
217 gettimeofday_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
219 return ((pst1->tv_sec - pst2->tv_sec) * 1000.0
220 + (pst1->tv_usec - pst2->tv_usec) / 1000.0);
224 gettimeofday_resolution (void)
226 /* Granularity of gettimeofday varies wildly between architectures.
227 However, it appears that on modern machines it tends to be better
228 than 1ms. Assume 100 usecs. */
231 #endif /* PTIMER_GETTIMEOFDAY */
234 /* Elapsed time measurement using the time(2) call: system time is
235 held in time_t, retrieved using time, and resolution is 1 second.
237 This method is a catch-all for non-Windows systems without
238 gettimeofday -- e.g. DOS or really old or non-standard Unix
241 typedef time_t ptimer_system_time;
243 #define IMPL_measure time_measure
244 #define IMPL_diff time_diff
245 #define IMPL_resolution time_resolution
248 time_measure (ptimer_system_time *pst)
254 time_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
256 return 1000.0 * (*pst1 - *pst2);
260 time_resolution (void)
264 #endif /* PTIMER_TIME */
266 #ifdef PTIMER_WINDOWS
267 /* Elapsed time measurement on Windows: where high-resolution timers
268 are available, time is stored in a LARGE_INTEGER and retrieved
269 using QueryPerformanceCounter. Otherwise, it is stored in a DWORD
270 and retrieved using GetTickCount.
272 This method is used on Windows. */
275 DWORD lores; /* In case GetTickCount is used */
276 LARGE_INTEGER hires; /* In case high-resolution timer is used */
277 } ptimer_system_time;
279 #define IMPL_init windows_init
280 #define IMPL_measure windows_measure
281 #define IMPL_diff windows_diff
282 #define IMPL_resolution windows_resolution
284 /* Whether high-resolution timers are used. Set by ptimer_initialize_once
285 the first time ptimer_new is called. */
286 static int windows_hires_timers;
288 /* Frequency of high-resolution timers -- number of updates per
289 millisecond. Calculated the first time ptimer_new is called
290 provided that high-resolution timers are available. */
291 static double windows_hires_msfreq;
298 QueryPerformanceFrequency (&freq);
299 if (freq.QuadPart != 0)
301 windows_hires_timers = 1;
302 windows_hires_msfreq = (double) freq.QuadPart / 1000.0;
307 windows_measure (ptimer_system_time *pst)
309 if (windows_hires_timers)
310 QueryPerformanceCounter (&pst->hires);
312 /* Where hires counters are not available, use GetTickCount rather
313 GetSystemTime, because it is unaffected by clock skew and
314 simpler to use. Note that overflows don't affect us because we
315 never use absolute values of the ticker, only the
317 pst->lores = GetTickCount ();
321 windows_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
323 if (windows_hires_timers)
324 return (pst1->hires.QuadPart - pst2->hires.QuadPart) / windows_hires_msfreq;
326 return pst1->lores - pst2->lores;
330 windows_resolution (void)
332 if (windows_hires_timers)
333 return 1.0 / windows_hires_msfreq;
335 return 10; /* according to MSDN */
337 #endif /* PTIMER_WINDOWS */
339 /* The code below this point is independent of timer implementation. */
342 /* The starting point in time which, subtracted from the current
343 time, yields elapsed time. */
344 ptimer_system_time start;
346 /* The most recent elapsed time, calculated by ptimer_measure().
347 Measured in milliseconds. */
350 /* Approximately, the time elapsed between the true start of the
351 measurement and the time represented by START. This is used for
352 adjustment when clock skew is detected. */
353 double elapsed_pre_start;
356 /* Allocate a new timer and reset it. Return the new timer. */
361 struct ptimer *pt = xnew0 (struct ptimer);
363 static int init_done;
374 /* Free the resources associated with the timer. Its further use is
378 ptimer_destroy (struct ptimer *pt)
383 /* Reset timer PT. This establishes the starting point from which
384 ptimer_read() will return the number of elapsed milliseconds.
385 It is allowed to reset a previously used timer. */
388 ptimer_reset (struct ptimer *pt)
390 /* Set the start time to the current time. */
391 IMPL_measure (&pt->start);
392 pt->elapsed_last = 0;
393 pt->elapsed_pre_start = 0;
396 /* Measure the elapsed time since timer creation/reset and return it
397 to the caller. The value remains stored for further reads by
400 This function causes the timer to call gettimeofday (or time(),
401 etc.) to update its idea of current time. To get the elapsed
402 interval in milliseconds, use ptimer_read.
404 This function handles clock skew, i.e. time that moves backwards is
408 ptimer_measure (struct ptimer *pt)
410 ptimer_system_time now;
414 elapsed = pt->elapsed_pre_start + IMPL_diff (&now, &pt->start);
416 /* Ideally we'd just return the difference between NOW and
417 pt->start. However, the system timer can be set back, and we
418 could return a value smaller than when we were last called, even
419 a negative value. Both of these would confuse the callers, which
420 expect us to return monotonically nondecreasing values.
422 Therefore: if ELAPSED is smaller than its previous known value,
423 we reset pt->start to the current time and effectively start
424 measuring from this point. But since we don't want the elapsed
425 value to start from zero, we set elapsed_pre_start to the last
426 elapsed time and increment all future calculations by that
429 This cannot happen with Windows and POSIX monotonic/highres
430 timers, but the check is not expensive. */
432 if (elapsed < pt->elapsed_last)
435 pt->elapsed_pre_start = pt->elapsed_last;
436 elapsed = pt->elapsed_last;
439 pt->elapsed_last = elapsed;
443 /* Return the elapsed time in milliseconds between the last call to
444 ptimer_reset and the last call to ptimer_update. */
447 ptimer_read (const struct ptimer *pt)
449 return pt->elapsed_last;
452 /* Return the assessed resolution of the timer implementation, in
453 milliseconds. This is used by code that tries to substitute a
454 better value for timers that have returned zero. */
457 ptimer_resolution (void)
459 return IMPL_resolution ();