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>
69 /* Cygwin currently (as of 2005-04-08, Cygwin 1.5.14) lacks clock_getres,
70 but still defines _POSIX_TIMERS! Because of that we simply use the
71 Windows timers under Cygwin. */
83 /* Depending on the OS and availability of gettimeofday(), one and
84 only one of PTIMER_POSIX, PTIMER_GETTIMEOFDAY, PTIMER_WINDOWS, or
85 PTIMER_TIME will be defined. */
88 #undef PTIMER_GETTIMEOFDAY
92 #if defined(WINDOWS) || defined(__CYGWIN__)
93 # define PTIMER_WINDOWS /* use Windows timers */
95 # if _POSIX_TIMERS - 0 > 0
96 # define PTIMER_POSIX /* use POSIX timers (clock_gettime) */
98 # ifdef HAVE_GETTIMEOFDAY
99 # define PTIMER_GETTIMEOFDAY /* use gettimeofday */
107 /* Elapsed time measurement using POSIX timers: system time is held in
108 struct timespec, time is retrieved using clock_gettime, and
109 resolution using clock_getres.
111 This method is used on Unix systems that implement POSIX
114 typedef struct timespec ptimer_system_time;
116 #define IMPL_init posix_init
117 #define IMPL_measure posix_measure
118 #define IMPL_diff posix_diff
119 #define IMPL_resolution posix_resolution
121 /* clock_id to use for POSIX clocks. This tries to use
122 CLOCK_MONOTONIC where available, CLOCK_REALTIME otherwise. */
123 static int posix_clock_id;
125 /* Resolution of the clock, in milliseconds. */
126 static double posix_millisec_resolution;
128 /* Decide which clock_id to use. */
133 /* List of clocks we want to support: some systems support monotonic
134 clocks, Solaris has "high resolution" clock (sometimes
135 unavailable except to superuser), and all should support the
137 #define NO_SYSCONF_CHECK -1
138 static const struct {
142 #if defined(_POSIX_MONOTONIC_CLOCK) && _POSIX_MONOTONIC_CLOCK - 0 >= 0
143 { CLOCK_MONOTONIC, _SC_MONOTONIC_CLOCK },
146 { CLOCK_HIGHRES, NO_SYSCONF_CHECK },
148 { CLOCK_REALTIME, NO_SYSCONF_CHECK },
152 /* Determine the clock we can use. For a clock to be usable, it
153 must be confirmed with sysconf (where applicable) and with
154 clock_getres. If no clock is found, CLOCK_REALTIME is used. */
156 for (i = 0; i < countof (clocks); i++)
159 if (clocks[i].sysconf_name != NO_SYSCONF_CHECK)
160 if (sysconf (clocks[i].sysconf_name) < 0)
161 continue; /* sysconf claims this clock is unavailable */
162 if (clock_getres (clocks[i].id, &r) < 0)
163 continue; /* clock_getres doesn't work for this clock */
164 posix_clock_id = clocks[i].id;
165 posix_millisec_resolution = r.tv_sec * 1000.0 + r.tv_nsec / 1000000.0;
166 /* Guard against broken clock_getres returning nonsensical
168 if (posix_millisec_resolution == 0)
169 posix_millisec_resolution = 1;
172 if (i == countof (clocks))
174 /* If no clock was found, it means that clock_getres failed for
175 the realtime clock. */
176 logprintf (LOG_NOTQUIET, _("Cannot get REALTIME clock frequency: %s\n"),
178 /* Use CLOCK_REALTIME, but invent a plausible resolution. */
179 posix_clock_id = CLOCK_REALTIME;
180 posix_millisec_resolution = 1;
185 posix_measure (ptimer_system_time *pst)
187 clock_gettime (posix_clock_id, pst);
191 posix_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
193 return ((pst1->tv_sec - pst2->tv_sec) * 1000.0
194 + (pst1->tv_nsec - pst2->tv_nsec) / 1000000.0);
198 posix_resolution (void)
200 return posix_millisec_resolution;
202 #endif /* PTIMER_POSIX */
204 #ifdef PTIMER_GETTIMEOFDAY
205 /* Elapsed time measurement using gettimeofday: system time is held in
206 struct timeval, retrieved using gettimeofday, and resolution is
209 This method is used Unix systems without POSIX timers. */
211 typedef struct timeval ptimer_system_time;
213 #define IMPL_measure gettimeofday_measure
214 #define IMPL_diff gettimeofday_diff
215 #define IMPL_resolution gettimeofday_resolution
218 gettimeofday_measure (ptimer_system_time *pst)
220 gettimeofday (pst, NULL);
224 gettimeofday_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
226 return ((pst1->tv_sec - pst2->tv_sec) * 1000.0
227 + (pst1->tv_usec - pst2->tv_usec) / 1000.0);
231 gettimeofday_resolution (void)
233 /* Granularity of gettimeofday varies wildly between architectures.
234 However, it appears that on modern machines it tends to be better
235 than 1ms. Assume 100 usecs. */
238 #endif /* PTIMER_GETTIMEOFDAY */
241 /* Elapsed time measurement using the time(2) call: system time is
242 held in time_t, retrieved using time, and resolution is 1 second.
244 This method is a catch-all for non-Windows systems without
245 gettimeofday -- e.g. DOS or really old or non-standard Unix
248 typedef time_t ptimer_system_time;
250 #define IMPL_measure time_measure
251 #define IMPL_diff time_diff
252 #define IMPL_resolution time_resolution
255 time_measure (ptimer_system_time *pst)
261 time_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
263 return 1000.0 * (*pst1 - *pst2);
267 time_resolution (void)
271 #endif /* PTIMER_TIME */
273 #ifdef PTIMER_WINDOWS
274 /* Elapsed time measurement on Windows: where high-resolution timers
275 are available, time is stored in a LARGE_INTEGER and retrieved
276 using QueryPerformanceCounter. Otherwise, it is stored in a DWORD
277 and retrieved using GetTickCount.
279 This method is used on Windows. */
282 DWORD lores; /* In case GetTickCount is used */
283 LARGE_INTEGER hires; /* In case high-resolution timer is used */
284 } ptimer_system_time;
286 #define IMPL_init windows_init
287 #define IMPL_measure windows_measure
288 #define IMPL_diff windows_diff
289 #define IMPL_resolution windows_resolution
291 /* Whether high-resolution timers are used. Set by ptimer_initialize_once
292 the first time ptimer_new is called. */
293 static int windows_hires_timers;
295 /* Frequency of high-resolution timers -- number of updates per
296 millisecond. Calculated the first time ptimer_new is called
297 provided that high-resolution timers are available. */
298 static double windows_hires_msfreq;
305 QueryPerformanceFrequency (&freq);
306 if (freq.QuadPart != 0)
308 windows_hires_timers = 1;
309 windows_hires_msfreq = (double) freq.QuadPart / 1000.0;
314 windows_measure (ptimer_system_time *pst)
316 if (windows_hires_timers)
317 QueryPerformanceCounter (&pst->hires);
319 /* Where hires counters are not available, use GetTickCount rather
320 GetSystemTime, because it is unaffected by clock skew and
321 simpler to use. Note that overflows don't affect us because we
322 never use absolute values of the ticker, only the
324 pst->lores = GetTickCount ();
328 windows_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
330 if (windows_hires_timers)
331 return (pst1->hires.QuadPart - pst2->hires.QuadPart) / windows_hires_msfreq;
333 return pst1->lores - pst2->lores;
337 windows_resolution (void)
339 if (windows_hires_timers)
340 return 1.0 / windows_hires_msfreq;
342 return 10; /* according to MSDN */
344 #endif /* PTIMER_WINDOWS */
346 /* The code below this point is independent of timer implementation. */
349 /* The starting point in time which, subtracted from the current
350 time, yields elapsed time. */
351 ptimer_system_time start;
353 /* The most recent elapsed time, calculated by ptimer_measure().
354 Measured in milliseconds. */
357 /* Approximately, the time elapsed between the true start of the
358 measurement and the time represented by START. This is used for
359 adjustment when clock skew is detected. */
360 double elapsed_pre_start;
363 /* Allocate a new timer and reset it. Return the new timer. */
368 struct ptimer *pt = xnew0 (struct ptimer);
370 static int init_done;
381 /* Free the resources associated with the timer. Its further use is
385 ptimer_destroy (struct ptimer *pt)
390 /* Reset timer PT. This establishes the starting point from which
391 ptimer_read() will return the number of elapsed milliseconds.
392 It is allowed to reset a previously used timer. */
395 ptimer_reset (struct ptimer *pt)
397 /* Set the start time to the current time. */
398 IMPL_measure (&pt->start);
399 pt->elapsed_last = 0;
400 pt->elapsed_pre_start = 0;
403 /* Measure the elapsed time since timer creation/reset and return it
404 to the caller. The value remains stored for further reads by
407 This function causes the timer to call gettimeofday (or time(),
408 etc.) to update its idea of current time. To get the elapsed
409 interval in milliseconds, use ptimer_read.
411 This function handles clock skew, i.e. time that moves backwards is
415 ptimer_measure (struct ptimer *pt)
417 ptimer_system_time now;
421 elapsed = pt->elapsed_pre_start + IMPL_diff (&now, &pt->start);
423 /* Ideally we'd just return the difference between NOW and
424 pt->start. However, the system timer can be set back, and we
425 could return a value smaller than when we were last called, even
426 a negative value. Both of these would confuse the callers, which
427 expect us to return monotonically nondecreasing values.
429 Therefore: if ELAPSED is smaller than its previous known value,
430 we reset pt->start to the current time and effectively start
431 measuring from this point. But since we don't want the elapsed
432 value to start from zero, we set elapsed_pre_start to the last
433 elapsed time and increment all future calculations by that
436 This cannot happen with Windows and POSIX monotonic/highres
437 timers, but the check is not expensive. */
439 if (elapsed < pt->elapsed_last)
442 pt->elapsed_pre_start = pt->elapsed_last;
443 elapsed = pt->elapsed_last;
446 pt->elapsed_last = elapsed;
450 /* Return the elapsed time in milliseconds between the last call to
451 ptimer_reset and the last call to ptimer_update. */
454 ptimer_read (const struct ptimer *pt)
456 return pt->elapsed_last;
459 /* Return the assessed resolution of the timer implementation, in
460 milliseconds. This is used by code that tries to substitute a
461 better value for timers that have returned zero. */
464 ptimer_resolution (void)
466 return IMPL_resolution ();