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 operate in milliseconds, but return floating point values
43 that can be more precise. For example, to measure the time it
44 takes to run a loop, you can use something like:
46 ptimer *tmr = ptimer_new ();
49 double msecs = ptimer_measure ();
50 printf ("The loop took %.2f ms\n", msecs); */
58 #else /* not HAVE_STRING_H */
60 #endif /* not HAVE_STRING_H */
61 #include <sys/types.h>
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
85 # define PTIMER_WINDOWS /* use Windows timers */
87 # if _POSIX_TIMERS > 0
88 # define PTIMER_POSIX /* use POSIX timers (clock_gettime) */
90 # ifdef HAVE_GETTIMEOFDAY
91 # define PTIMER_GETTIMEOFDAY /* use gettimeofday */
99 /* Elapsed time measurement using POSIX timers: system time is held in
100 struct timespec, time is retrieved using clock_gettime, and
101 resolution using clock_getres.
103 This method is used on Unix systems that implement POSIX
106 typedef struct timespec ptimer_system_time;
108 #define IMPL_init posix_init
109 #define IMPL_measure posix_measure
110 #define IMPL_diff posix_diff
111 #define IMPL_resolution posix_resolution
113 /* clock_id to use for POSIX clocks. This tries to use
114 CLOCK_MONOTONIC where available, CLOCK_REALTIME otherwise. */
115 static int posix_clock_id;
117 /* Resolution of the clock, in milliseconds. */
118 static double posix_millisec_resolution;
120 /* Decide which clock_id to use. */
125 /* List of clocks we want to support: some systems support monotonic
126 clocks, Solaris has "high resolution" clock (sometimes
127 unavailable except to superuser), and all should support the
129 #define NO_SYSCONF_CHECK -1
130 static const struct {
134 #if defined(_POSIX_MONOTONIC_CLOCK) && _POSIX_MONOTONIC_CLOCK >= 0
135 { CLOCK_MONOTONIC, _SC_MONOTONIC_CLOCK },
138 { CLOCK_HIGHRES, NO_SYSCONF_CHECK },
140 { CLOCK_REALTIME, NO_SYSCONF_CHECK },
144 /* Determine the clock we can use. For a clock to be usable, it
145 must be confirmed with sysconf (where applicable) and with
146 clock_getres. If no clock is found, CLOCK_REALTIME is used. */
148 for (i = 0; i < countof (clocks); i++)
151 if (clocks[i].sysconf_name != NO_SYSCONF_CHECK)
152 if (sysconf (clocks[i].sysconf_name) < 0)
153 continue; /* sysconf claims this clock is unavailable */
154 if (clock_getres (clocks[i].id, &r) < 0)
155 continue; /* clock_getres doesn't work for this clock */
156 posix_clock_id = clocks[i].id;
157 posix_millisec_resolution = r.tv_sec * 1000.0 + r.tv_nsec / 1000000.0;
158 /* Guard against broken clock_getres returning nonsensical
160 if (posix_millisec_resolution == 0)
161 posix_millisec_resolution = 1;
164 if (i == countof (clocks))
166 /* If no clock was found, it means that clock_getres failed for
167 the realtime clock. */
168 logprintf (LOG_NOTQUIET, _("Cannot get REALTIME clock frequency: %s\n"),
170 /* Use CLOCK_REALTIME, but invent a plausible resolution. */
171 posix_clock_id = CLOCK_REALTIME;
172 posix_millisec_resolution = 1;
177 posix_measure (ptimer_system_time *pst)
179 clock_gettime (posix_clock_id, pst);
183 posix_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
185 return ((pst1->tv_sec - pst2->tv_sec) * 1000.0
186 + (pst1->tv_nsec - pst2->tv_nsec) / 1000000.0);
190 posix_resolution (void)
192 return posix_millisec_resolution;
194 #endif /* PTIMER_POSIX */
196 #ifdef PTIMER_GETTIMEOFDAY
197 /* Elapsed time measurement using gettimeofday: system time is held in
198 struct timeval, retrieved using gettimeofday, and resolution is
201 This method is used Unix systems without POSIX timers. */
203 typedef struct timeval ptimer_system_time;
205 #define IMPL_measure gettimeofday_measure
206 #define IMPL_diff gettimeofday_diff
207 #define IMPL_resolution gettimeofday_resolution
210 gettimeofday_measure (ptimer_system_time *pst)
212 gettimeofday (pst, NULL);
216 gettimeofday_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
218 return ((pst1->tv_sec - pst2->tv_sec) * 1000.0
219 + (pst1->tv_usec - pst2->tv_usec) / 1000.0);
223 gettimeofday_resolution (void)
225 /* Granularity of gettimeofday varies wildly between architectures.
226 However, it appears that on modern machines it tends to be better
227 than 1ms. Assume 100 usecs. */
230 #endif /* PTIMER_GETTIMEOFDAY */
233 /* Elapsed time measurement using the time(2) call: system time is
234 held in time_t, retrieved using time, and resolution is 1 second.
236 This method is a catch-all for non-Windows systems without
237 gettimeofday -- e.g. DOS or really old or non-standard Unix
240 typedef time_t ptimer_system_time;
242 #define IMPL_measure time_measure
243 #define IMPL_diff time_diff
244 #define IMPL_resolution time_resolution
247 time_measure (ptimer_system_time *pst)
253 time_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
255 return 1000.0 * (*pst1 - *pst2);
259 time_resolution (void)
263 #endif /* PTIMER_TIME */
265 #ifdef PTIMER_WINDOWS
266 /* Elapsed time measurement on Windows: where high-resolution timers
267 are available, time is stored in a LARGE_INTEGER and retrieved
268 using QueryPerformanceCounter. Otherwise, it is stored in a DWORD
269 and retrieved using GetTickCount.
271 This method is used on Windows. */
274 DWORD lores; /* In case GetTickCount is used */
275 LARGE_INTEGER hires; /* In case high-resolution timer is used */
276 } ptimer_system_time;
278 #define IMPL_init windows_init
279 #define IMPL_measure windows_measure
280 #define IMPL_diff windows_diff
281 #define IMPL_resolution windows_resolution
283 /* Whether high-resolution timers are used. Set by ptimer_initialize_once
284 the first time ptimer_new is called. */
285 static int windows_hires_timers;
287 /* Frequency of high-resolution timers -- number of updates per
288 millisecond. Calculated the first time ptimer_new is called
289 provided that high-resolution timers are available. */
290 static double windows_hires_msfreq;
297 QueryPerformanceFrequency (&freq);
298 if (freq.QuadPart != 0)
300 windows_hires_timers = 1;
301 windows_hires_msfreq = (double) freq.QuadPart / 1000.0;
306 windows_measure (ptimer_system_time *pst)
308 if (windows_hires_timers)
309 QueryPerformanceCounter (&pst->hires);
311 /* Where hires counters are not available, use GetTickCount rather
312 GetSystemTime, because it is unaffected by clock skew and
313 simpler to use. Note that overflows don't affect us because we
314 never use absolute values of the ticker, only the
316 pst->lores = GetTickCount ();
320 windows_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
322 if (windows_hires_timers)
323 return (pst1->hires.QuadPart - pst2->hires.QuadPart) / windows_hires_msfreq;
325 return pst1->lores - pst2->lores;
329 windows_resolution (void)
331 if (windows_hires_timers)
332 return 1.0 / windows_hires_msfreq;
334 return 10; /* according to MSDN */
336 #endif /* PTIMER_WINDOWS */
338 /* The code below this point is independent of timer implementation. */
341 /* Whether the start time has been set. */
344 /* The starting point in time which, subtracted from the current
345 time, yields elapsed time. */
346 ptimer_system_time start;
348 /* The most recent elapsed time, calculated by ptimer_measure().
349 Measured in milliseconds. */
352 /* Approximately, the time elapsed between the true start of the
353 measurement and the time represented by START. This is used for
354 adjustment when clock skew is detected. */
355 double elapsed_pre_start;
358 /* Allocate a new timer and reset it. Return the new timer. */
363 struct ptimer *wt = xnew0 (struct ptimer);
365 static int init_done;
376 /* Free the resources associated with the timer. Its further use is
380 ptimer_destroy (struct ptimer *wt)
385 /* Reset timer WT. This establishes the starting point from which
386 ptimer_read() will return the number of elapsed milliseconds.
387 It is allowed to reset a previously used timer. */
390 ptimer_reset (struct ptimer *wt)
392 /* Set the start time to the current time. */
393 IMPL_measure (&wt->start);
394 wt->elapsed_last = 0;
395 wt->elapsed_pre_start = 0;
399 /* Measure the elapsed time since timer creation/reset and return it
400 to the caller. The value remains stored for further reads by
403 This function causes the timer to call gettimeofday (or time(),
404 etc.) to update its idea of current time. To get the elapsed
405 interval in milliseconds, use ptimer_read.
407 This function handles clock skew, i.e. time that moves backwards is
411 ptimer_measure (struct ptimer *wt)
413 ptimer_system_time now;
416 assert (wt->initialized != 0);
419 elapsed = wt->elapsed_pre_start + IMPL_diff (&now, &wt->start);
421 /* Ideally we'd just return the difference between NOW and
422 wt->start. However, the system timer can be set back, and we
423 could return a value smaller than when we were last called, even
424 a negative value. Both of these would confuse the callers, which
425 expect us to return monotonically nondecreasing values.
427 Therefore: if ELAPSED is smaller than its previous known value,
428 we reset wt->start to the current time and effectively start
429 measuring from this point. But since we don't want the elapsed
430 value to start from zero, we set elapsed_pre_start to the last
431 elapsed time and increment all future calculations by that
434 This cannot happen with Windows and POSIX monotonic/highres
435 timers, but the check is not expensive. */
437 if (elapsed < wt->elapsed_last)
440 wt->elapsed_pre_start = wt->elapsed_last;
441 elapsed = wt->elapsed_last;
444 wt->elapsed_last = elapsed;
448 /* Return the elapsed time in milliseconds between the last call to
449 ptimer_reset and the last call to ptimer_update. */
452 ptimer_read (const struct ptimer *wt)
454 return wt->elapsed_last;
457 /* Return the assessed resolution of the timer implementation, in
458 milliseconds. This is used by code that tries to substitute a
459 better value for timers that have returned zero. */
462 ptimer_resolution (void)
464 return IMPL_resolution ();