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); */
65 /* Cygwin currently (as of 2005-04-08, Cygwin 1.5.14) lacks clock_getres,
66 but still defines _POSIX_TIMERS! Because of that we simply use the
67 Windows timers under Cygwin. */
75 /* Depending on the OS and availability of gettimeofday(), one and
76 only one of PTIMER_POSIX, PTIMER_GETTIMEOFDAY, PTIMER_WINDOWS, or
77 PTIMER_TIME will be defined. */
80 #undef PTIMER_GETTIMEOFDAY
84 #if defined(WINDOWS) || defined(__CYGWIN__)
85 # define PTIMER_WINDOWS /* use Windows timers */
86 #elif _POSIX_TIMERS - 0 > 0
87 # define PTIMER_POSIX /* use POSIX timers (clock_gettime) */
88 #elif defined(HAVE_GETTIMEOFDAY)
89 # define PTIMER_GETTIMEOFDAY /* use gettimeofday */
95 /* Elapsed time measurement using POSIX timers: system time is held in
96 struct timespec, time is retrieved using clock_gettime, and
97 resolution using clock_getres.
99 This method is used on Unix systems that implement POSIX
102 typedef struct timespec ptimer_system_time;
104 #define IMPL_init posix_init
105 #define IMPL_measure posix_measure
106 #define IMPL_diff posix_diff
107 #define IMPL_resolution posix_resolution
109 /* clock_id to use for POSIX clocks. This tries to use
110 CLOCK_MONOTONIC where available, CLOCK_REALTIME otherwise. */
111 static int posix_clock_id;
113 /* Resolution of the clock, in milliseconds. */
114 static double posix_millisec_resolution;
116 /* Decide which clock_id to use. */
121 /* List of clocks we want to support: some systems support monotonic
122 clocks, Solaris has "high resolution" clock (sometimes
123 unavailable except to superuser), and all should support the
125 #define NO_SYSCONF_CHECK -1
126 static const struct {
130 #if defined(_POSIX_MONOTONIC_CLOCK) && _POSIX_MONOTONIC_CLOCK - 0 >= 0
131 { CLOCK_MONOTONIC, _SC_MONOTONIC_CLOCK },
134 { CLOCK_HIGHRES, NO_SYSCONF_CHECK },
136 { CLOCK_REALTIME, NO_SYSCONF_CHECK },
140 /* Determine the clock we can use. For a clock to be usable, it
141 must be confirmed with sysconf (where applicable) and with
142 clock_getres. If no clock is found, CLOCK_REALTIME is used. */
144 for (i = 0; i < countof (clocks); i++)
147 if (clocks[i].sysconf_name != NO_SYSCONF_CHECK)
148 if (sysconf (clocks[i].sysconf_name) < 0)
149 continue; /* sysconf claims this clock is unavailable */
150 if (clock_getres (clocks[i].id, &r) < 0)
151 continue; /* clock_getres doesn't work for this clock */
152 posix_clock_id = clocks[i].id;
153 posix_millisec_resolution = r.tv_sec * 1000.0 + r.tv_nsec / 1000000.0;
154 /* Guard against broken clock_getres returning nonsensical
156 if (posix_millisec_resolution == 0)
157 posix_millisec_resolution = 1;
160 if (i == countof (clocks))
162 /* If no clock was found, it means that clock_getres failed for
163 the realtime clock. */
164 logprintf (LOG_NOTQUIET, _("Cannot get REALTIME clock frequency: %s\n"),
166 /* Use CLOCK_REALTIME, but invent a plausible resolution. */
167 posix_clock_id = CLOCK_REALTIME;
168 posix_millisec_resolution = 1;
173 posix_measure (ptimer_system_time *pst)
175 clock_gettime (posix_clock_id, pst);
179 posix_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
181 return ((pst1->tv_sec - pst2->tv_sec) * 1000.0
182 + (pst1->tv_nsec - pst2->tv_nsec) / 1000000.0);
186 posix_resolution (void)
188 return posix_millisec_resolution;
190 #endif /* PTIMER_POSIX */
192 #ifdef PTIMER_GETTIMEOFDAY
193 /* Elapsed time measurement using gettimeofday: system time is held in
194 struct timeval, retrieved using gettimeofday, and resolution is
197 This method is used Unix systems without POSIX timers. */
199 typedef struct timeval ptimer_system_time;
201 #define IMPL_measure gettimeofday_measure
202 #define IMPL_diff gettimeofday_diff
203 #define IMPL_resolution gettimeofday_resolution
206 gettimeofday_measure (ptimer_system_time *pst)
208 gettimeofday (pst, NULL);
212 gettimeofday_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
214 return ((pst1->tv_sec - pst2->tv_sec) * 1000.0
215 + (pst1->tv_usec - pst2->tv_usec) / 1000.0);
219 gettimeofday_resolution (void)
221 /* Granularity of gettimeofday varies wildly between architectures.
222 However, it appears that on modern machines it tends to be better
223 than 1ms. Assume 100 usecs. */
226 #endif /* PTIMER_GETTIMEOFDAY */
229 /* Elapsed time measurement using the time(2) call: system time is
230 held in time_t, retrieved using time, and resolution is 1 second.
232 This method is a catch-all for non-Windows systems without
233 gettimeofday -- e.g. DOS or really old or non-standard Unix
236 typedef time_t ptimer_system_time;
238 #define IMPL_measure time_measure
239 #define IMPL_diff time_diff
240 #define IMPL_resolution time_resolution
243 time_measure (ptimer_system_time *pst)
249 time_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
251 return 1000.0 * (*pst1 - *pst2);
255 time_resolution (void)
259 #endif /* PTIMER_TIME */
261 #ifdef PTIMER_WINDOWS
262 /* Elapsed time measurement on Windows: where high-resolution timers
263 are available, time is stored in a LARGE_INTEGER and retrieved
264 using QueryPerformanceCounter. Otherwise, it is stored in a DWORD
265 and retrieved using GetTickCount.
267 This method is used on Windows. */
270 DWORD lores; /* In case GetTickCount is used */
271 LARGE_INTEGER hires; /* In case high-resolution timer is used */
272 } ptimer_system_time;
274 #define IMPL_init windows_init
275 #define IMPL_measure windows_measure
276 #define IMPL_diff windows_diff
277 #define IMPL_resolution windows_resolution
279 /* Whether high-resolution timers are used. Set by ptimer_initialize_once
280 the first time ptimer_new is called. */
281 static int windows_hires_timers;
283 /* Frequency of high-resolution timers -- number of updates per
284 millisecond. Calculated the first time ptimer_new is called
285 provided that high-resolution timers are available. */
286 static double windows_hires_msfreq;
293 QueryPerformanceFrequency (&freq);
294 if (freq.QuadPart != 0)
296 windows_hires_timers = 1;
297 windows_hires_msfreq = (double) freq.QuadPart / 1000.0;
302 windows_measure (ptimer_system_time *pst)
304 if (windows_hires_timers)
305 QueryPerformanceCounter (&pst->hires);
307 /* Where hires counters are not available, use GetTickCount rather
308 GetSystemTime, because it is unaffected by clock skew and
309 simpler to use. Note that overflows don't affect us because we
310 never use absolute values of the ticker, only the
312 pst->lores = GetTickCount ();
316 windows_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
318 if (windows_hires_timers)
319 return (pst1->hires.QuadPart - pst2->hires.QuadPart) / windows_hires_msfreq;
321 return pst1->lores - pst2->lores;
325 windows_resolution (void)
327 if (windows_hires_timers)
328 return 1.0 / windows_hires_msfreq;
330 return 10; /* according to MSDN */
332 #endif /* PTIMER_WINDOWS */
334 /* The code below this point is independent of timer implementation. */
337 /* The starting point in time which, subtracted from the current
338 time, yields elapsed time. */
339 ptimer_system_time start;
341 /* The most recent elapsed time, calculated by ptimer_measure().
342 Measured in milliseconds. */
345 /* Approximately, the time elapsed between the true start of the
346 measurement and the time represented by START. This is used for
347 adjustment when clock skew is detected. */
348 double elapsed_pre_start;
351 /* Allocate a new timer and reset it. Return the new timer. */
356 struct ptimer *pt = xnew0 (struct ptimer);
358 static int init_done;
369 /* Free the resources associated with the timer. Its further use is
373 ptimer_destroy (struct ptimer *pt)
378 /* Reset timer PT. This establishes the starting point from which
379 ptimer_read() will return the number of elapsed milliseconds.
380 It is allowed to reset a previously used timer. */
383 ptimer_reset (struct ptimer *pt)
385 /* Set the start time to the current time. */
386 IMPL_measure (&pt->start);
387 pt->elapsed_last = 0;
388 pt->elapsed_pre_start = 0;
391 /* Measure the elapsed time since timer creation/reset and return it
392 to the caller. The value remains stored for further reads by
395 This function causes the timer to call gettimeofday (or time(),
396 etc.) to update its idea of current time. To get the elapsed
397 interval in milliseconds, use ptimer_read.
399 This function handles clock skew, i.e. time that moves backwards is
403 ptimer_measure (struct ptimer *pt)
405 ptimer_system_time now;
409 elapsed = pt->elapsed_pre_start + IMPL_diff (&now, &pt->start);
411 /* Ideally we'd just return the difference between NOW and
412 pt->start. However, the system timer can be set back, and we
413 could return a value smaller than when we were last called, even
414 a negative value. Both of these would confuse the callers, which
415 expect us to return monotonically nondecreasing values.
417 Therefore: if ELAPSED is smaller than its previous known value,
418 we reset pt->start to the current time and effectively start
419 measuring from this point. But since we don't want the elapsed
420 value to start from zero, we set elapsed_pre_start to the last
421 elapsed time and increment all future calculations by that
424 This cannot happen with Windows and POSIX monotonic/highres
425 timers, but the check is not expensive. */
427 if (elapsed < pt->elapsed_last)
430 pt->elapsed_pre_start = pt->elapsed_last;
431 elapsed = pt->elapsed_last;
434 pt->elapsed_last = elapsed;
438 /* Return the elapsed time in milliseconds between the last call to
439 ptimer_reset and the last call to ptimer_update. */
442 ptimer_read (const struct ptimer *pt)
444 return pt->elapsed_last;
447 /* Return the assessed resolution of the timer implementation, in
448 milliseconds. This is used by code that tries to substitute a
449 better value for timers that have returned zero. */
452 ptimer_resolution (void)
454 return IMPL_resolution ();