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, one and only one of PTIMER_POSIX,
76 PTIMER_GETTIMEOFDAY, or PTIMER_WINDOWS will be defined. */
79 #undef PTIMER_GETTIMEOFDAY
82 #if defined(WINDOWS) || defined(__CYGWIN__)
83 # define PTIMER_WINDOWS /* use Windows timers */
84 #elif _POSIX_TIMERS - 0 > 0
85 # define PTIMER_POSIX /* use POSIX timers (clock_gettime) */
87 # define PTIMER_GETTIMEOFDAY /* use gettimeofday */
91 /* Elapsed time measurement using POSIX timers: system time is held in
92 struct timespec, time is retrieved using clock_gettime, and
93 resolution using clock_getres.
95 This method is used on Unix systems that implement POSIX
98 typedef struct timespec ptimer_system_time;
100 #define IMPL_init posix_init
101 #define IMPL_measure posix_measure
102 #define IMPL_diff posix_diff
103 #define IMPL_resolution posix_resolution
105 /* clock_id to use for POSIX clocks. This tries to use
106 CLOCK_MONOTONIC where available, CLOCK_REALTIME otherwise. */
107 static int posix_clock_id;
109 /* Resolution of the clock, in milliseconds. */
110 static double posix_millisec_resolution;
112 /* Decide which clock_id to use. */
117 /* List of clocks we want to support: some systems support monotonic
118 clocks, Solaris has "high resolution" clock (sometimes
119 unavailable except to superuser), and all should support the
121 #define NO_SYSCONF_CHECK -1
122 static const struct {
126 #if defined(_POSIX_MONOTONIC_CLOCK) && _POSIX_MONOTONIC_CLOCK - 0 >= 0
127 { CLOCK_MONOTONIC, _SC_MONOTONIC_CLOCK },
130 { CLOCK_HIGHRES, NO_SYSCONF_CHECK },
132 { CLOCK_REALTIME, NO_SYSCONF_CHECK },
136 /* Determine the clock we can use. For a clock to be usable, it
137 must be confirmed with sysconf (where applicable) and with
138 clock_getres. If no clock is found, CLOCK_REALTIME is used. */
140 for (i = 0; i < countof (clocks); i++)
143 if (clocks[i].sysconf_name != NO_SYSCONF_CHECK)
144 if (sysconf (clocks[i].sysconf_name) < 0)
145 continue; /* sysconf claims this clock is unavailable */
146 if (clock_getres (clocks[i].id, &r) < 0)
147 continue; /* clock_getres doesn't work for this clock */
148 posix_clock_id = clocks[i].id;
149 posix_millisec_resolution = r.tv_sec * 1000.0 + r.tv_nsec / 1000000.0;
150 /* Guard against broken clock_getres returning nonsensical
152 if (posix_millisec_resolution == 0)
153 posix_millisec_resolution = 1;
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_millisec_resolution = 1;
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) * 1000.0
178 + (pst1->tv_nsec - pst2->tv_nsec) / 1000000.0);
182 posix_resolution (void)
184 return posix_millisec_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) * 1000.0
211 + (pst1->tv_usec - pst2->tv_usec) / 1000.0);
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 millisecond. Calculated the first time ptimer_new is called
248 provided that high-resolution timers are available. */
249 static double windows_hires_msfreq;
256 QueryPerformanceFrequency (&freq);
257 if (freq.QuadPart != 0)
259 windows_hires_timers = true;
260 windows_hires_msfreq = (double) freq.QuadPart / 1000.0;
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_msfreq;
284 return pst1->lores - pst2->lores;
288 windows_resolution (void)
290 if (windows_hires_timers)
291 return 1.0 / windows_hires_msfreq;
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().
305 Measured in milliseconds. */
308 /* Approximately, the time elapsed between the true start of the
309 measurement and the time represented by START. This is used for
310 adjustment when clock skew is detected. */
311 double elapsed_pre_start;
314 /* Allocate a new timer and reset it. Return the new timer. */
319 struct ptimer *pt = xnew0 (struct ptimer);
321 static bool init_done;
332 /* Free the resources associated with the timer. Its further use is
336 ptimer_destroy (struct ptimer *pt)
341 /* Reset timer PT. This establishes the starting point from which
342 ptimer_read() will return the number of elapsed milliseconds.
343 It is allowed to reset a previously used timer. */
346 ptimer_reset (struct ptimer *pt)
348 /* Set the start time to the current time. */
349 IMPL_measure (&pt->start);
350 pt->elapsed_last = 0;
351 pt->elapsed_pre_start = 0;
354 /* Measure the elapsed time since timer creation/reset and return it
355 to the caller. The value remains stored for further reads by
358 This function causes the timer to call gettimeofday (or time(),
359 etc.) to update its idea of current time. To get the elapsed
360 interval in milliseconds, use ptimer_read.
362 This function handles clock skew, i.e. time that moves backwards is
366 ptimer_measure (struct ptimer *pt)
368 ptimer_system_time now;
372 elapsed = pt->elapsed_pre_start + IMPL_diff (&now, &pt->start);
374 /* Ideally we'd just return the difference between NOW and
375 pt->start. However, the system timer can be set back, and we
376 could return a value smaller than when we were last called, even
377 a negative value. Both of these would confuse the callers, which
378 expect us to return monotonically nondecreasing values.
380 Therefore: if ELAPSED is smaller than its previous known value,
381 we reset pt->start to the current time and effectively start
382 measuring from this point. But since we don't want the elapsed
383 value to start from zero, we set elapsed_pre_start to the last
384 elapsed time and increment all future calculations by that
387 This cannot happen with Windows and POSIX monotonic/highres
388 timers, but the check is not expensive. */
390 if (elapsed < pt->elapsed_last)
393 pt->elapsed_pre_start = pt->elapsed_last;
394 elapsed = pt->elapsed_last;
397 pt->elapsed_last = elapsed;
401 /* Return the elapsed time in milliseconds between the last call to
402 ptimer_reset and the last call to ptimer_update. */
405 ptimer_read (const struct ptimer *pt)
407 return pt->elapsed_last;
410 /* Return the assessed resolution of the timer implementation, in
411 milliseconds. This is used by code that tries to substitute a
412 better value for timers that have returned zero. */
415 ptimer_resolution (void)
417 return IMPL_resolution ();