2 Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Free Software
5 This file is part of GNU Wget.
7 GNU Wget is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3 of the License, or
10 (at your option) any later version.
12 GNU Wget is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with Wget. If not, see <http://www.gnu.org/licenses/>.
20 Additional permission under GNU GPL version 3 section 7
22 If you modify this program, or any covered work, by linking or
23 combining it with the OpenSSL project's OpenSSL library (or a
24 modified version of that library), containing parts covered by the
25 terms of the OpenSSL or SSLeay licenses, the Free Software Foundation
26 grants you additional permission to convey the resulting work.
27 Corresponding Source for a non-source form of such a combination
28 shall include the source code for the parts of OpenSSL used as well
29 as that of the covered work. */
31 /* This file implements "portable timers" (ptimers), objects that
32 measure elapsed time using the primitives most appropriate for the
33 underlying operating system. The entry points are:
35 ptimer_new -- creates a timer.
36 ptimer_reset -- resets the timer's elapsed time to zero.
37 ptimer_measure -- measure and return the time elapsed since
38 creation or last reset.
39 ptimer_read -- reads the last measured elapsed value.
40 ptimer_destroy -- destroy the timer.
41 ptimer_granularity -- returns the approximate granularity of the timers.
43 Timers measure time in seconds, returning the timings as floating
44 point numbers, so they can carry as much precision as the
45 underlying system timer supports. For example, to measure the time
46 it takes to run a loop, you can use something like:
48 ptimer *tmr = ptimer_new ();
51 double secs = ptimer_measure ();
52 printf ("The loop took %.2fs\n", secs); */
64 #ifdef HAVE_SYS_TIME_H
65 # include <sys/time.h>
68 /* Cygwin currently (as of 2005-04-08, Cygwin 1.5.14) lacks clock_getres,
69 but still defines _POSIX_TIMERS! Because of that we simply use the
70 Windows timers under Cygwin. */
78 /* Depending on the OS, one and only one of PTIMER_POSIX,
79 PTIMER_GETTIMEOFDAY, or PTIMER_WINDOWS will be defined. */
82 #undef PTIMER_GETTIMEOFDAY
85 #if defined(WINDOWS) || defined(__CYGWIN__)
86 # define PTIMER_WINDOWS /* use Windows timers */
87 #elif _POSIX_TIMERS - 0 > 0
88 # define PTIMER_POSIX /* use POSIX timers (clock_gettime) */
90 # define PTIMER_GETTIMEOFDAY /* use gettimeofday */
94 /* Elapsed time measurement using POSIX timers: system time is held in
95 struct timespec, time is retrieved using clock_gettime, and
96 resolution using clock_getres.
98 This method is used on Unix systems that implement POSIX
101 typedef struct timespec ptimer_system_time;
103 #define IMPL_init posix_init
104 #define IMPL_measure posix_measure
105 #define IMPL_diff posix_diff
106 #define IMPL_resolution posix_resolution
108 /* clock_id to use for POSIX clocks. This tries to use
109 CLOCK_MONOTONIC where available, CLOCK_REALTIME otherwise. */
110 static int posix_clock_id;
112 /* Resolution of the clock, initialized in posix_init. */
113 static double posix_clock_resolution;
115 /* Decide which clock_id to use. */
120 /* List of clocks we want to support: some systems support monotonic
121 clocks, Solaris has "high resolution" clock (sometimes
122 unavailable except to superuser), and all should support the
124 #define NO_SYSCONF_CHECK -1
125 static const struct {
129 #if defined(_POSIX_MONOTONIC_CLOCK) && _POSIX_MONOTONIC_CLOCK - 0 >= 0
130 { CLOCK_MONOTONIC, _SC_MONOTONIC_CLOCK },
133 { CLOCK_HIGHRES, NO_SYSCONF_CHECK },
135 { CLOCK_REALTIME, NO_SYSCONF_CHECK },
139 /* Determine the clock we can use. For a clock to be usable, it
140 must be confirmed with sysconf (where applicable) and with
141 clock_getres. If no clock is found, CLOCK_REALTIME is used. */
143 for (i = 0; i < countof (clocks); i++)
146 if (clocks[i].sysconf_name != NO_SYSCONF_CHECK)
147 if (sysconf (clocks[i].sysconf_name) < 0)
148 continue; /* sysconf claims this clock is unavailable */
149 if (clock_getres (clocks[i].id, &r) < 0)
150 continue; /* clock_getres doesn't work for this clock */
151 posix_clock_id = clocks[i].id;
152 posix_clock_resolution = (double) r.tv_sec + r.tv_nsec / 1e9;
153 /* Guard against nonsense returned by a broken clock_getres. */
154 if (posix_clock_resolution == 0)
155 posix_clock_resolution = 1e-3;
158 if (i == countof (clocks))
160 /* If no clock was found, it means that clock_getres failed for
161 the realtime clock. */
162 logprintf (LOG_NOTQUIET, _("Cannot get REALTIME clock frequency: %s\n"),
164 /* Use CLOCK_REALTIME, but invent a plausible resolution. */
165 posix_clock_id = CLOCK_REALTIME;
166 posix_clock_resolution = 1e-3;
171 posix_measure (ptimer_system_time *pst)
173 clock_gettime (posix_clock_id, pst);
177 posix_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
179 return ((pst1->tv_sec - pst2->tv_sec)
180 + (pst1->tv_nsec - pst2->tv_nsec) / 1e9);
184 posix_resolution (void)
186 return posix_clock_resolution;
188 #endif /* PTIMER_POSIX */
190 #ifdef PTIMER_GETTIMEOFDAY
191 /* Elapsed time measurement using gettimeofday: system time is held in
192 struct timeval, retrieved using gettimeofday, and resolution is
195 This method is used Unix systems without POSIX timers. */
197 typedef struct timeval ptimer_system_time;
199 #define IMPL_measure gettimeofday_measure
200 #define IMPL_diff gettimeofday_diff
201 #define IMPL_resolution gettimeofday_resolution
204 gettimeofday_measure (ptimer_system_time *pst)
206 gettimeofday (pst, NULL);
210 gettimeofday_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
212 return ((pst1->tv_sec - pst2->tv_sec)
213 + (pst1->tv_usec - pst2->tv_usec) / 1e6);
217 gettimeofday_resolution (void)
219 /* Granularity of gettimeofday varies wildly between architectures.
220 However, it appears that on modern machines it tends to be better
221 than 1ms. Assume 100 usecs. */
224 #endif /* PTIMER_GETTIMEOFDAY */
226 #ifdef PTIMER_WINDOWS
227 /* Elapsed time measurement on Windows: where high-resolution timers
228 are available, time is stored in a LARGE_INTEGER and retrieved
229 using QueryPerformanceCounter. Otherwise, it is stored in a DWORD
230 and retrieved using GetTickCount.
232 This method is used on Windows. */
235 DWORD lores; /* In case GetTickCount is used */
236 LARGE_INTEGER hires; /* In case high-resolution timer is used */
237 } ptimer_system_time;
239 #define IMPL_init windows_init
240 #define IMPL_measure windows_measure
241 #define IMPL_diff windows_diff
242 #define IMPL_resolution windows_resolution
244 /* Whether high-resolution timers are used. Set by ptimer_initialize_once
245 the first time ptimer_new is called. */
246 static bool windows_hires_timers;
248 /* Frequency of high-resolution timers -- number of updates per
249 second. Calculated the first time ptimer_new is called provided
250 that high-resolution timers are available. */
251 static double windows_hires_freq;
258 QueryPerformanceFrequency (&freq);
259 if (freq.QuadPart != 0)
261 windows_hires_timers = true;
262 windows_hires_freq = (double) freq.QuadPart;
267 windows_measure (ptimer_system_time *pst)
269 if (windows_hires_timers)
270 QueryPerformanceCounter (&pst->hires);
272 /* Where hires counters are not available, use GetTickCount rather
273 GetSystemTime, because it is unaffected by clock skew and
274 simpler to use. Note that overflows don't affect us because we
275 never use absolute values of the ticker, only the
277 pst->lores = GetTickCount ();
281 windows_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
283 if (windows_hires_timers)
284 return (pst1->hires.QuadPart - pst2->hires.QuadPart) / windows_hires_freq;
286 return pst1->lores - pst2->lores;
290 windows_resolution (void)
292 if (windows_hires_timers)
293 return 1.0 / windows_hires_freq;
295 return 10; /* according to MSDN */
297 #endif /* PTIMER_WINDOWS */
299 /* The code below this point is independent of timer implementation. */
302 /* The starting point in time which, subtracted from the current
303 time, yields elapsed time. */
304 ptimer_system_time start;
306 /* The most recent elapsed time, calculated by ptimer_measure(). */
309 /* Approximately, the time elapsed between the true start of the
310 measurement and the time represented by START. This is used for
311 adjustment when clock skew is detected. */
312 double elapsed_pre_start;
315 /* Allocate a new timer and reset it. Return the new timer. */
320 struct ptimer *pt = xnew0 (struct ptimer);
322 static bool init_done;
333 /* Free the resources associated with the timer. Its further use is
337 ptimer_destroy (struct ptimer *pt)
342 /* Reset timer PT. This establishes the starting point from which
343 ptimer_measure() will return the elapsed time in seconds. It is
344 allowed to reset a previously used timer. */
347 ptimer_reset (struct ptimer *pt)
349 /* Set the start time to the current time. */
350 IMPL_measure (&pt->start);
351 pt->elapsed_last = 0;
352 pt->elapsed_pre_start = 0;
355 /* Measure the elapsed time since timer creation/reset. This causes
356 the timer to internally call clock_gettime (or gettimeofday, etc.)
357 to update its idea of current time. The time is returned, but is
358 also stored for later access through ptimer_read().
360 This function handles clock skew, i.e. time that moves backwards is
364 ptimer_measure (struct ptimer *pt)
366 ptimer_system_time now;
370 elapsed = pt->elapsed_pre_start + IMPL_diff (&now, &pt->start);
372 /* Ideally we'd just return the difference between NOW and
373 pt->start. However, the system timer can be set back, and we
374 could return a value smaller than when we were last called, even
375 a negative value. Both of these would confuse the callers, which
376 expect us to return monotonically nondecreasing values.
378 Therefore: if ELAPSED is smaller than its previous known value,
379 we reset pt->start to the current time and effectively start
380 measuring from this point. But since we don't want the elapsed
381 value to start from zero, we set elapsed_pre_start to the last
382 elapsed time and increment all future calculations by that
385 This cannot happen with Windows and POSIX monotonic/highres
386 timers, but the check is not expensive. */
388 if (elapsed < pt->elapsed_last)
391 pt->elapsed_pre_start = pt->elapsed_last;
392 elapsed = pt->elapsed_last;
395 pt->elapsed_last = elapsed;
399 /* Return the most recent elapsed time measured with ptimer_measure.
400 If ptimer_measure has not yet been called since the timer was
401 created or reset, this returns 0. */
404 ptimer_read (const struct ptimer *pt)
406 return pt->elapsed_last;
409 /* Return the assessed resolution of the timer implementation, in
410 seconds. This is used by code that tries to substitute a better
411 value for timers that have returned zero. */
414 ptimer_resolution (void)
416 return IMPL_resolution ();