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); */
53 #define USE_GNULIB_ALLOC
65 #ifdef HAVE_SYS_TIME_H
66 # include <sys/time.h>
69 /* Cygwin currently (as of 2005-04-08, Cygwin 1.5.14) lacks clock_getres,
70 but still defines _POSIX_TIMERS! Because of that we simply use the
71 Windows timers under Cygwin. */
79 /* Depending on the OS, one and only one of PTIMER_POSIX,
80 PTIMER_GETTIMEOFDAY, or PTIMER_WINDOWS will be defined. */
83 #undef PTIMER_GETTIMEOFDAY
86 #if defined(WINDOWS) || defined(__CYGWIN__)
87 # define PTIMER_WINDOWS /* use Windows timers */
88 #elif _POSIX_TIMERS - 0 > 0
89 # define PTIMER_POSIX /* use POSIX timers (clock_gettime) */
91 # define PTIMER_GETTIMEOFDAY /* use gettimeofday */
95 /* Elapsed time measurement using POSIX timers: system time is held in
96 struct timespec, time is retrieved using clock_gettime, and
97 resolution using clock_getres.
99 This method is used on Unix systems that implement POSIX
102 typedef struct timespec ptimer_system_time;
104 #define IMPL_init posix_init
105 #define IMPL_measure posix_measure
106 #define IMPL_diff posix_diff
107 #define IMPL_resolution posix_resolution
109 /* clock_id to use for POSIX clocks. This tries to use
110 CLOCK_MONOTONIC where available, CLOCK_REALTIME otherwise. */
111 static int posix_clock_id;
113 /* Resolution of the clock, initialized in posix_init. */
114 static double posix_clock_resolution;
116 /* Decide which clock_id to use. */
121 /* List of clocks we want to support: some systems support monotonic
122 clocks, Solaris has "high resolution" clock (sometimes
123 unavailable except to superuser), and all should support the
125 #define NO_SYSCONF_CHECK -1
126 static const struct {
130 #if defined(_POSIX_MONOTONIC_CLOCK) && _POSIX_MONOTONIC_CLOCK - 0 >= 0
131 { CLOCK_MONOTONIC, _SC_MONOTONIC_CLOCK },
134 { CLOCK_HIGHRES, NO_SYSCONF_CHECK },
136 { CLOCK_REALTIME, NO_SYSCONF_CHECK },
140 /* Determine the clock we can use. For a clock to be usable, it
141 must be confirmed with sysconf (where applicable) and with
142 clock_getres. If no clock is found, CLOCK_REALTIME is used. */
144 for (i = 0; i < countof (clocks); i++)
147 if (clocks[i].sysconf_name != NO_SYSCONF_CHECK)
148 if (sysconf (clocks[i].sysconf_name) < 0)
149 continue; /* sysconf claims this clock is unavailable */
150 if (clock_getres (clocks[i].id, &r) < 0)
151 continue; /* clock_getres doesn't work for this clock */
152 posix_clock_id = clocks[i].id;
153 posix_clock_resolution = (double) r.tv_sec + r.tv_nsec / 1e9;
154 /* Guard against nonsense returned by a broken clock_getres. */
155 if (posix_clock_resolution == 0)
156 posix_clock_resolution = 1e-3;
159 if (i == countof (clocks))
161 /* If no clock was found, it means that clock_getres failed for
162 the realtime clock. */
163 logprintf (LOG_NOTQUIET, _("Cannot get REALTIME clock frequency: %s\n"),
165 /* Use CLOCK_REALTIME, but invent a plausible resolution. */
166 posix_clock_id = CLOCK_REALTIME;
167 posix_clock_resolution = 1e-3;
172 posix_measure (ptimer_system_time *pst)
174 clock_gettime (posix_clock_id, pst);
178 posix_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
180 return ((pst1->tv_sec - pst2->tv_sec)
181 + (pst1->tv_nsec - pst2->tv_nsec) / 1e9);
185 posix_resolution (void)
187 return posix_clock_resolution;
189 #endif /* PTIMER_POSIX */
191 #ifdef PTIMER_GETTIMEOFDAY
192 /* Elapsed time measurement using gettimeofday: system time is held in
193 struct timeval, retrieved using gettimeofday, and resolution is
196 This method is used Unix systems without POSIX timers. */
198 typedef struct timeval ptimer_system_time;
200 #define IMPL_measure gettimeofday_measure
201 #define IMPL_diff gettimeofday_diff
202 #define IMPL_resolution gettimeofday_resolution
205 gettimeofday_measure (ptimer_system_time *pst)
207 gettimeofday (pst, NULL);
211 gettimeofday_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
213 return ((pst1->tv_sec - pst2->tv_sec)
214 + (pst1->tv_usec - pst2->tv_usec) / 1e6);
218 gettimeofday_resolution (void)
220 /* Granularity of gettimeofday varies wildly between architectures.
221 However, it appears that on modern machines it tends to be better
222 than 1ms. Assume 100 usecs. */
225 #endif /* PTIMER_GETTIMEOFDAY */
227 #ifdef PTIMER_WINDOWS
228 /* Elapsed time measurement on Windows: where high-resolution timers
229 are available, time is stored in a LARGE_INTEGER and retrieved
230 using QueryPerformanceCounter. Otherwise, it is stored in a DWORD
231 and retrieved using GetTickCount.
233 This method is used on Windows. */
236 DWORD lores; /* In case GetTickCount is used */
237 LARGE_INTEGER hires; /* In case high-resolution timer is used */
238 } ptimer_system_time;
240 #define IMPL_init windows_init
241 #define IMPL_measure windows_measure
242 #define IMPL_diff windows_diff
243 #define IMPL_resolution windows_resolution
245 /* Whether high-resolution timers are used. Set by ptimer_initialize_once
246 the first time ptimer_new is called. */
247 static bool windows_hires_timers;
249 /* Frequency of high-resolution timers -- number of updates per
250 second. Calculated the first time ptimer_new is called provided
251 that high-resolution timers are available. */
252 static double windows_hires_freq;
259 QueryPerformanceFrequency (&freq);
260 if (freq.QuadPart != 0)
262 windows_hires_timers = true;
263 windows_hires_freq = (double) freq.QuadPart;
268 windows_measure (ptimer_system_time *pst)
270 if (windows_hires_timers)
271 QueryPerformanceCounter (&pst->hires);
273 /* Where hires counters are not available, use GetTickCount rather
274 GetSystemTime, because it is unaffected by clock skew and
275 simpler to use. Note that overflows don't affect us because we
276 never use absolute values of the ticker, only the
278 pst->lores = GetTickCount ();
282 windows_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
284 if (windows_hires_timers)
285 return (pst1->hires.QuadPart - pst2->hires.QuadPart) / windows_hires_freq;
287 return pst1->lores - pst2->lores;
291 windows_resolution (void)
293 if (windows_hires_timers)
294 return 1.0 / windows_hires_freq;
296 return 10; /* according to MSDN */
298 #endif /* PTIMER_WINDOWS */
300 /* The code below this point is independent of timer implementation. */
303 /* The starting point in time which, subtracted from the current
304 time, yields elapsed time. */
305 ptimer_system_time start;
307 /* The most recent elapsed time, calculated by ptimer_measure(). */
310 /* Approximately, the time elapsed between the true start of the
311 measurement and the time represented by START. This is used for
312 adjustment when clock skew is detected. */
313 double elapsed_pre_start;
316 /* Allocate a new timer and reset it. Return the new timer. */
321 struct ptimer *pt = xnew0 (struct ptimer);
323 static bool init_done;
334 /* Free the resources associated with the timer. Its further use is
338 ptimer_destroy (struct ptimer *pt)
343 /* Reset timer PT. This establishes the starting point from which
344 ptimer_measure() will return the elapsed time in seconds. It is
345 allowed to reset a previously used timer. */
348 ptimer_reset (struct ptimer *pt)
350 /* Set the start time to the current time. */
351 IMPL_measure (&pt->start);
352 pt->elapsed_last = 0;
353 pt->elapsed_pre_start = 0;
356 /* Measure the elapsed time since timer creation/reset. This causes
357 the timer to internally call clock_gettime (or gettimeofday, etc.)
358 to update its idea of current time. The time is returned, but is
359 also stored for later access through ptimer_read().
361 This function handles clock skew, i.e. time that moves backwards is
365 ptimer_measure (struct ptimer *pt)
367 ptimer_system_time now;
371 elapsed = pt->elapsed_pre_start + IMPL_diff (&now, &pt->start);
373 /* Ideally we'd just return the difference between NOW and
374 pt->start. However, the system timer can be set back, and we
375 could return a value smaller than when we were last called, even
376 a negative value. Both of these would confuse the callers, which
377 expect us to return monotonically nondecreasing values.
379 Therefore: if ELAPSED is smaller than its previous known value,
380 we reset pt->start to the current time and effectively start
381 measuring from this point. But since we don't want the elapsed
382 value to start from zero, we set elapsed_pre_start to the last
383 elapsed time and increment all future calculations by that
386 This cannot happen with Windows and POSIX monotonic/highres
387 timers, but the check is not expensive. */
389 if (elapsed < pt->elapsed_last)
392 pt->elapsed_pre_start = pt->elapsed_last;
393 elapsed = pt->elapsed_last;
396 pt->elapsed_last = elapsed;
400 /* Return the most recent elapsed time measured with ptimer_measure.
401 If ptimer_measure has not yet been called since the timer was
402 created or reset, this returns 0. */
405 ptimer_read (const struct ptimer *pt)
407 return pt->elapsed_last;
410 /* Return the assessed resolution of the timer implementation, in
411 seconds. This is used by code that tries to substitute a better
412 value for timers that have returned zero. */
415 ptimer_resolution (void)
417 return IMPL_resolution ();