2 Copyright (C) 2005-2006 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. */
76 /* Depending on the OS, one and only one of PTIMER_POSIX,
77 PTIMER_GETTIMEOFDAY, or PTIMER_WINDOWS will be defined. */
80 #undef PTIMER_GETTIMEOFDAY
83 #if defined(WINDOWS) || defined(__CYGWIN__)
84 # define PTIMER_WINDOWS /* use Windows timers */
85 #elif _POSIX_TIMERS - 0 > 0
86 # define PTIMER_POSIX /* use POSIX timers (clock_gettime) */
88 # define PTIMER_GETTIMEOFDAY /* use gettimeofday */
92 /* Elapsed time measurement using POSIX timers: system time is held in
93 struct timespec, time is retrieved using clock_gettime, and
94 resolution using clock_getres.
96 This method is used on Unix systems that implement POSIX
99 typedef struct timespec ptimer_system_time;
101 #define IMPL_init posix_init
102 #define IMPL_measure posix_measure
103 #define IMPL_diff posix_diff
104 #define IMPL_resolution posix_resolution
106 /* clock_id to use for POSIX clocks. This tries to use
107 CLOCK_MONOTONIC where available, CLOCK_REALTIME otherwise. */
108 static int posix_clock_id;
110 /* Resolution of the clock, initialized in posix_init. */
111 static double posix_clock_resolution;
113 /* Decide which clock_id to use. */
118 /* List of clocks we want to support: some systems support monotonic
119 clocks, Solaris has "high resolution" clock (sometimes
120 unavailable except to superuser), and all should support the
122 #define NO_SYSCONF_CHECK -1
123 static const struct {
127 #if defined(_POSIX_MONOTONIC_CLOCK) && _POSIX_MONOTONIC_CLOCK - 0 >= 0
128 { CLOCK_MONOTONIC, _SC_MONOTONIC_CLOCK },
131 { CLOCK_HIGHRES, NO_SYSCONF_CHECK },
133 { CLOCK_REALTIME, NO_SYSCONF_CHECK },
137 /* Determine the clock we can use. For a clock to be usable, it
138 must be confirmed with sysconf (where applicable) and with
139 clock_getres. If no clock is found, CLOCK_REALTIME is used. */
141 for (i = 0; i < countof (clocks); i++)
144 if (clocks[i].sysconf_name != NO_SYSCONF_CHECK)
145 if (sysconf (clocks[i].sysconf_name) < 0)
146 continue; /* sysconf claims this clock is unavailable */
147 if (clock_getres (clocks[i].id, &r) < 0)
148 continue; /* clock_getres doesn't work for this clock */
149 posix_clock_id = clocks[i].id;
150 posix_clock_resolution = (double) r.tv_sec + r.tv_nsec / 1e9;
151 /* Guard against nonsense returned by a broken clock_getres. */
152 if (posix_clock_resolution == 0)
153 posix_clock_resolution = 1e-3;
156 if (i == countof (clocks))
158 /* If no clock was found, it means that clock_getres failed for
159 the realtime clock. */
160 logprintf (LOG_NOTQUIET, _("Cannot get REALTIME clock frequency: %s\n"),
162 /* Use CLOCK_REALTIME, but invent a plausible resolution. */
163 posix_clock_id = CLOCK_REALTIME;
164 posix_clock_resolution = 1e-3;
169 posix_measure (ptimer_system_time *pst)
171 clock_gettime (posix_clock_id, pst);
175 posix_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
177 return ((pst1->tv_sec - pst2->tv_sec)
178 + (pst1->tv_nsec - pst2->tv_nsec) / 1e9);
182 posix_resolution (void)
184 return posix_clock_resolution;
186 #endif /* PTIMER_POSIX */
188 #ifdef PTIMER_GETTIMEOFDAY
189 /* Elapsed time measurement using gettimeofday: system time is held in
190 struct timeval, retrieved using gettimeofday, and resolution is
193 This method is used Unix systems without POSIX timers. */
195 typedef struct timeval ptimer_system_time;
197 #define IMPL_measure gettimeofday_measure
198 #define IMPL_diff gettimeofday_diff
199 #define IMPL_resolution gettimeofday_resolution
202 gettimeofday_measure (ptimer_system_time *pst)
204 gettimeofday (pst, NULL);
208 gettimeofday_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
210 return ((pst1->tv_sec - pst2->tv_sec)
211 + (pst1->tv_usec - pst2->tv_usec) / 1e6);
215 gettimeofday_resolution (void)
217 /* Granularity of gettimeofday varies wildly between architectures.
218 However, it appears that on modern machines it tends to be better
219 than 1ms. Assume 100 usecs. */
222 #endif /* PTIMER_GETTIMEOFDAY */
224 #ifdef PTIMER_WINDOWS
225 /* Elapsed time measurement on Windows: where high-resolution timers
226 are available, time is stored in a LARGE_INTEGER and retrieved
227 using QueryPerformanceCounter. Otherwise, it is stored in a DWORD
228 and retrieved using GetTickCount.
230 This method is used on Windows. */
233 DWORD lores; /* In case GetTickCount is used */
234 LARGE_INTEGER hires; /* In case high-resolution timer is used */
235 } ptimer_system_time;
237 #define IMPL_init windows_init
238 #define IMPL_measure windows_measure
239 #define IMPL_diff windows_diff
240 #define IMPL_resolution windows_resolution
242 /* Whether high-resolution timers are used. Set by ptimer_initialize_once
243 the first time ptimer_new is called. */
244 static bool windows_hires_timers;
246 /* Frequency of high-resolution timers -- number of updates per
247 second. Calculated the first time ptimer_new is called provided
248 that high-resolution timers are available. */
249 static double windows_hires_freq;
256 QueryPerformanceFrequency (&freq);
257 if (freq.QuadPart != 0)
259 windows_hires_timers = true;
260 windows_hires_freq = (double) freq.QuadPart;
265 windows_measure (ptimer_system_time *pst)
267 if (windows_hires_timers)
268 QueryPerformanceCounter (&pst->hires);
270 /* Where hires counters are not available, use GetTickCount rather
271 GetSystemTime, because it is unaffected by clock skew and
272 simpler to use. Note that overflows don't affect us because we
273 never use absolute values of the ticker, only the
275 pst->lores = GetTickCount ();
279 windows_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
281 if (windows_hires_timers)
282 return (pst1->hires.QuadPart - pst2->hires.QuadPart) / windows_hires_freq;
284 return pst1->lores - pst2->lores;
288 windows_resolution (void)
290 if (windows_hires_timers)
291 return 1.0 / windows_hires_freq;
293 return 10; /* according to MSDN */
295 #endif /* PTIMER_WINDOWS */
297 /* The code below this point is independent of timer implementation. */
300 /* The starting point in time which, subtracted from the current
301 time, yields elapsed time. */
302 ptimer_system_time start;
304 /* The most recent elapsed time, calculated by ptimer_measure(). */
307 /* Approximately, the time elapsed between the true start of the
308 measurement and the time represented by START. This is used for
309 adjustment when clock skew is detected. */
310 double elapsed_pre_start;
313 /* Allocate a new timer and reset it. Return the new timer. */
318 struct ptimer *pt = xnew0 (struct ptimer);
320 static bool init_done;
331 /* Free the resources associated with the timer. Its further use is
335 ptimer_destroy (struct ptimer *pt)
340 /* Reset timer PT. This establishes the starting point from which
341 ptimer_measure() will return the elapsed time in seconds. It is
342 allowed to reset a previously used timer. */
345 ptimer_reset (struct ptimer *pt)
347 /* Set the start time to the current time. */
348 IMPL_measure (&pt->start);
349 pt->elapsed_last = 0;
350 pt->elapsed_pre_start = 0;
353 /* Measure the elapsed time since timer creation/reset. This causes
354 the timer to internally call clock_gettime (or gettimeofday, etc.)
355 to update its idea of current time. The time is returned, but is
356 also stored for later access through ptimer_read().
358 This function handles clock skew, i.e. time that moves backwards is
362 ptimer_measure (struct ptimer *pt)
364 ptimer_system_time now;
368 elapsed = pt->elapsed_pre_start + IMPL_diff (&now, &pt->start);
370 /* Ideally we'd just return the difference between NOW and
371 pt->start. However, the system timer can be set back, and we
372 could return a value smaller than when we were last called, even
373 a negative value. Both of these would confuse the callers, which
374 expect us to return monotonically nondecreasing values.
376 Therefore: if ELAPSED is smaller than its previous known value,
377 we reset pt->start to the current time and effectively start
378 measuring from this point. But since we don't want the elapsed
379 value to start from zero, we set elapsed_pre_start to the last
380 elapsed time and increment all future calculations by that
383 This cannot happen with Windows and POSIX monotonic/highres
384 timers, but the check is not expensive. */
386 if (elapsed < pt->elapsed_last)
389 pt->elapsed_pre_start = pt->elapsed_last;
390 elapsed = pt->elapsed_last;
393 pt->elapsed_last = elapsed;
397 /* Return the most recent elapsed time measured with ptimer_measure.
398 If ptimer_measure has not yet been called since the timer was
399 created or reset, this returns 0. */
402 ptimer_read (const struct ptimer *pt)
404 return pt->elapsed_last;
407 /* Return the assessed resolution of the timer implementation, in
408 seconds. This is used by code that tries to substitute a better
409 value for timers that have returned zero. */
412 ptimer_resolution (void)
414 return IMPL_resolution ();