2 Copyright (C) 2005, 2006, 2007, 2008 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 Additional permission under GNU GPL version 3 section 7
21 If you modify this program, or any covered work, by linking or
22 combining it with the OpenSSL project's OpenSSL library (or a
23 modified version of that library), containing parts covered by the
24 terms of the OpenSSL or SSLeay licenses, the Free Software Foundation
25 grants you additional permission to convey the resulting work.
26 Corresponding Source for a non-source form of such a combination
27 shall include the source code for the parts of OpenSSL used as well
28 as that of the covered work. */
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 seconds, returning the timings as floating
43 point numbers, so they can carry as much precision as the
44 underlying system timer supports. For example, to measure the time
45 it takes to run a loop, you can use something like:
47 ptimer *tmr = ptimer_new ();
50 double secs = ptimer_measure ();
51 printf ("The loop took %.2fs\n", secs); */
63 #ifdef HAVE_SYS_TIME_H
64 # include <sys/time.h>
67 /* Cygwin currently (as of 2005-04-08, Cygwin 1.5.14) lacks clock_getres,
68 but still defines _POSIX_TIMERS! Because of that we simply use the
69 Windows timers under Cygwin. */
77 /* Depending on the OS, one and only one of PTIMER_POSIX,
78 PTIMER_GETTIMEOFDAY, or PTIMER_WINDOWS will be defined. */
81 #undef PTIMER_GETTIMEOFDAY
84 #if defined(WINDOWS) || defined(__CYGWIN__)
85 # define PTIMER_WINDOWS /* use Windows timers */
86 #elif _POSIX_TIMERS - 0 > 0
87 # define PTIMER_POSIX /* use POSIX timers (clock_gettime) */
89 # define PTIMER_GETTIMEOFDAY /* use gettimeofday */
93 /* Elapsed time measurement using POSIX timers: system time is held in
94 struct timespec, time is retrieved using clock_gettime, and
95 resolution using clock_getres.
97 This method is used on Unix systems that implement POSIX
100 typedef struct timespec ptimer_system_time;
102 #define IMPL_init posix_init
103 #define IMPL_measure posix_measure
104 #define IMPL_diff posix_diff
105 #define IMPL_resolution posix_resolution
107 /* clock_id to use for POSIX clocks. This tries to use
108 CLOCK_MONOTONIC where available, CLOCK_REALTIME otherwise. */
109 static int posix_clock_id;
111 /* Resolution of the clock, initialized in posix_init. */
112 static double posix_clock_resolution;
114 /* Decide which clock_id to use. */
119 /* List of clocks we want to support: some systems support monotonic
120 clocks, Solaris has "high resolution" clock (sometimes
121 unavailable except to superuser), and all should support the
123 #define NO_SYSCONF_CHECK -1
124 static const struct {
128 #if defined(_POSIX_MONOTONIC_CLOCK) && _POSIX_MONOTONIC_CLOCK - 0 >= 0
129 { CLOCK_MONOTONIC, _SC_MONOTONIC_CLOCK },
132 { CLOCK_HIGHRES, NO_SYSCONF_CHECK },
134 { CLOCK_REALTIME, NO_SYSCONF_CHECK },
138 /* Determine the clock we can use. For a clock to be usable, it
139 must be confirmed with sysconf (where applicable) and with
140 clock_getres. If no clock is found, CLOCK_REALTIME is used. */
142 for (i = 0; i < countof (clocks); i++)
145 if (clocks[i].sysconf_name != NO_SYSCONF_CHECK)
146 if (sysconf (clocks[i].sysconf_name) < 0)
147 continue; /* sysconf claims this clock is unavailable */
148 if (clock_getres (clocks[i].id, &r) < 0)
149 continue; /* clock_getres doesn't work for this clock */
150 posix_clock_id = clocks[i].id;
151 posix_clock_resolution = (double) r.tv_sec + r.tv_nsec / 1e9;
152 /* Guard against nonsense returned by a broken clock_getres. */
153 if (posix_clock_resolution == 0)
154 posix_clock_resolution = 1e-3;
157 if (i == countof (clocks))
159 /* If no clock was found, it means that clock_getres failed for
160 the realtime clock. */
161 logprintf (LOG_NOTQUIET, _("Cannot get REALTIME clock frequency: %s\n"),
163 /* Use CLOCK_REALTIME, but invent a plausible resolution. */
164 posix_clock_id = CLOCK_REALTIME;
165 posix_clock_resolution = 1e-3;
170 posix_measure (ptimer_system_time *pst)
172 clock_gettime (posix_clock_id, pst);
176 posix_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
178 return ((pst1->tv_sec - pst2->tv_sec)
179 + (pst1->tv_nsec - pst2->tv_nsec) / 1e9);
183 posix_resolution (void)
185 return posix_clock_resolution;
187 #endif /* PTIMER_POSIX */
189 #ifdef PTIMER_GETTIMEOFDAY
190 /* Elapsed time measurement using gettimeofday: system time is held in
191 struct timeval, retrieved using gettimeofday, and resolution is
194 This method is used Unix systems without POSIX timers. */
196 typedef struct timeval ptimer_system_time;
198 #define IMPL_measure gettimeofday_measure
199 #define IMPL_diff gettimeofday_diff
200 #define IMPL_resolution gettimeofday_resolution
203 gettimeofday_measure (ptimer_system_time *pst)
205 gettimeofday (pst, NULL);
209 gettimeofday_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
211 return ((pst1->tv_sec - pst2->tv_sec)
212 + (pst1->tv_usec - pst2->tv_usec) / 1e6);
216 gettimeofday_resolution (void)
218 /* Granularity of gettimeofday varies wildly between architectures.
219 However, it appears that on modern machines it tends to be better
220 than 1ms. Assume 100 usecs. */
223 #endif /* PTIMER_GETTIMEOFDAY */
225 #ifdef PTIMER_WINDOWS
226 /* Elapsed time measurement on Windows: where high-resolution timers
227 are available, time is stored in a LARGE_INTEGER and retrieved
228 using QueryPerformanceCounter. Otherwise, it is stored in a DWORD
229 and retrieved using GetTickCount.
231 This method is used on Windows. */
234 DWORD lores; /* In case GetTickCount is used */
235 LARGE_INTEGER hires; /* In case high-resolution timer is used */
236 } ptimer_system_time;
238 #define IMPL_init windows_init
239 #define IMPL_measure windows_measure
240 #define IMPL_diff windows_diff
241 #define IMPL_resolution windows_resolution
243 /* Whether high-resolution timers are used. Set by ptimer_initialize_once
244 the first time ptimer_new is called. */
245 static bool windows_hires_timers;
247 /* Frequency of high-resolution timers -- number of updates per
248 second. Calculated the first time ptimer_new is called provided
249 that high-resolution timers are available. */
250 static double windows_hires_freq;
257 QueryPerformanceFrequency (&freq);
258 if (freq.QuadPart != 0)
260 windows_hires_timers = true;
261 windows_hires_freq = (double) freq.QuadPart;
266 windows_measure (ptimer_system_time *pst)
268 if (windows_hires_timers)
269 QueryPerformanceCounter (&pst->hires);
271 /* Where hires counters are not available, use GetTickCount rather
272 GetSystemTime, because it is unaffected by clock skew and
273 simpler to use. Note that overflows don't affect us because we
274 never use absolute values of the ticker, only the
276 pst->lores = GetTickCount ();
280 windows_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
282 if (windows_hires_timers)
283 return (pst1->hires.QuadPart - pst2->hires.QuadPart) / windows_hires_freq;
285 return pst1->lores - pst2->lores;
289 windows_resolution (void)
291 if (windows_hires_timers)
292 return 1.0 / windows_hires_freq;
294 return 10; /* according to MSDN */
296 #endif /* PTIMER_WINDOWS */
298 /* The code below this point is independent of timer implementation. */
301 /* The starting point in time which, subtracted from the current
302 time, yields elapsed time. */
303 ptimer_system_time start;
305 /* The most recent elapsed time, calculated by ptimer_measure(). */
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_measure() will return the elapsed time in seconds. It is
343 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. This causes
355 the timer to internally call clock_gettime (or gettimeofday, etc.)
356 to update its idea of current time. The time is returned, but is
357 also stored for later access through ptimer_read().
359 This function handles clock skew, i.e. time that moves backwards is
363 ptimer_measure (struct ptimer *pt)
365 ptimer_system_time now;
369 elapsed = pt->elapsed_pre_start + IMPL_diff (&now, &pt->start);
371 /* Ideally we'd just return the difference between NOW and
372 pt->start. However, the system timer can be set back, and we
373 could return a value smaller than when we were last called, even
374 a negative value. Both of these would confuse the callers, which
375 expect us to return monotonically nondecreasing values.
377 Therefore: if ELAPSED is smaller than its previous known value,
378 we reset pt->start to the current time and effectively start
379 measuring from this point. But since we don't want the elapsed
380 value to start from zero, we set elapsed_pre_start to the last
381 elapsed time and increment all future calculations by that
384 This cannot happen with Windows and POSIX monotonic/highres
385 timers, but the check is not expensive. */
387 if (elapsed < pt->elapsed_last)
390 pt->elapsed_pre_start = pt->elapsed_last;
391 elapsed = pt->elapsed_last;
394 pt->elapsed_last = elapsed;
398 /* Return the most recent elapsed time measured with ptimer_measure.
399 If ptimer_measure has not yet been called since the timer was
400 created or reset, this returns 0. */
403 ptimer_read (const struct ptimer *pt)
405 return pt->elapsed_last;
408 /* Return the assessed resolution of the timer implementation, in
409 seconds. This is used by code that tries to substitute a better
410 value for timers that have returned zero. */
413 ptimer_resolution (void)
415 return IMPL_resolution ();