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Diffstat (limited to 'src/ptimer.c')
| -rw-r--r-- | src/ptimer.c | 413 |
1 files changed, 413 insertions, 0 deletions
diff --git a/src/ptimer.c b/src/ptimer.c new file mode 100644 index 0000000..2e5efbc --- /dev/null +++ b/src/ptimer.c @@ -0,0 +1,413 @@ +/* Portable timers. + Copyright (C) 2005-2011, 2015, 2018-2020 Free Software Foundation, + Inc. + +This file is part of GNU Wget. + +GNU Wget is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 3 of the License, or +(at your option) any later version. + +GNU Wget is distributed in the hope that it will be useful, +but WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +GNU General Public License for more details. + +You should have received a copy of the GNU General Public License +along with Wget. If not, see <http://www.gnu.org/licenses/>. + +Additional permission under GNU GPL version 3 section 7 + +If you modify this program, or any covered work, by linking or +combining it with the OpenSSL project's OpenSSL library (or a +modified version of that library), containing parts covered by the +terms of the OpenSSL or SSLeay licenses, the Free Software Foundation +grants you additional permission to convey the resulting work. +Corresponding Source for a non-source form of such a combination +shall include the source code for the parts of OpenSSL used as well +as that of the covered work. */ + +/* This file implements "portable timers" (ptimers), objects that + measure elapsed time using the primitives most appropriate for the + underlying operating system. The entry points are: + + ptimer_new -- creates a timer. + ptimer_reset -- resets the timer's elapsed time to zero. + ptimer_measure -- measure and return the time elapsed since + creation or last reset. + ptimer_read -- reads the last measured elapsed value. + ptimer_destroy -- destroy the timer. + ptimer_granularity -- returns the approximate granularity of the timers. + + Timers measure time in seconds, returning the timings as floating + point numbers, so they can carry as much precision as the + underlying system timer supports. For example, to measure the time + it takes to run a loop, you can use something like: + + ptimer *tmr = ptimer_new (); + while (...) + ... loop ... + double secs = ptimer_measure (); + printf ("The loop took %.2fs\n", secs); */ + +#include "wget.h" + +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <errno.h> +#include <unistd.h> +#include <time.h> +#include <sys/time.h> + +/* Cygwin currently (as of 2005-04-08, Cygwin 1.5.14) lacks clock_getres, + but still defines _POSIX_TIMERS! Because of that we simply use the + Windows timers under Cygwin. */ +#ifdef __CYGWIN__ +# include <windows.h> +#endif + +#include "utils.h" +#include "ptimer.h" + +/* Depending on the OS, one and only one of PTIMER_POSIX, + PTIMER_GETTIMEOFDAY, or PTIMER_WINDOWS will be defined. */ + +#undef PTIMER_POSIX +#undef PTIMER_GETTIMEOFDAY +#undef PTIMER_WINDOWS + +#if defined(WINDOWS) || defined(__CYGWIN__) +# define PTIMER_WINDOWS /* use Windows timers */ +#elif _POSIX_TIMERS - 0 > 0 +# define PTIMER_POSIX /* use POSIX timers (clock_gettime) */ +#else +# define PTIMER_GETTIMEOFDAY /* use gettimeofday */ +#endif + +#ifdef PTIMER_POSIX +/* Elapsed time measurement using POSIX timers: system time is held in + struct timespec, time is retrieved using clock_gettime, and + resolution using clock_getres. + + This method is used on Unix systems that implement POSIX + timers. */ + +typedef struct timespec ptimer_system_time; + +#define IMPL_init posix_init +#define IMPL_measure posix_measure +#define IMPL_diff posix_diff +#define IMPL_resolution posix_resolution + +/* clock_id to use for POSIX clocks. This tries to use + CLOCK_MONOTONIC where available, CLOCK_REALTIME otherwise. */ +static int posix_clock_id; + +/* Resolution of the clock, initialized in posix_init. */ +static double posix_clock_resolution; + +/* Decide which clock_id to use. */ + +static void +posix_init (void) +{ + /* List of clocks we want to support: some systems support monotonic + clocks, Solaris has "high resolution" clock (sometimes + unavailable except to superuser), and all should support the + real-time clock. */ +#define NO_SYSCONF_CHECK -1 + static const struct { + int id; + int sysconf_name; + } clocks[] = { +#if defined(_POSIX_MONOTONIC_CLOCK) && _POSIX_MONOTONIC_CLOCK - 0 >= 0 + { CLOCK_MONOTONIC, _SC_MONOTONIC_CLOCK }, +#endif +#ifdef CLOCK_HIGHRES + { CLOCK_HIGHRES, NO_SYSCONF_CHECK }, +#endif + { CLOCK_REALTIME, NO_SYSCONF_CHECK }, + }; + size_t i; + + /* Determine the clock we can use. For a clock to be usable, it + must be confirmed with sysconf (where applicable) and with + clock_getres. If no clock is found, CLOCK_REALTIME is used. */ + + for (i = 0; i < countof (clocks); i++) + { + struct timespec r; + if (clocks[i].sysconf_name != NO_SYSCONF_CHECK) + if (sysconf (clocks[i].sysconf_name) < 0) + continue; /* sysconf claims this clock is unavailable */ + if (clock_getres (clocks[i].id, &r) < 0) + continue; /* clock_getres doesn't work for this clock */ + posix_clock_id = clocks[i].id; + posix_clock_resolution = (double) r.tv_sec + r.tv_nsec / 1e9; + /* Guard against nonsense returned by a broken clock_getres. */ + if (posix_clock_resolution == 0) + posix_clock_resolution = 1e-3; + break; + } + if (i == countof (clocks)) + { + /* If no clock was found, it means that clock_getres failed for + the realtime clock. */ + logprintf (LOG_NOTQUIET, _("Cannot get REALTIME clock frequency: %s\n"), + strerror (errno)); + /* Use CLOCK_REALTIME, but invent a plausible resolution. */ + posix_clock_id = CLOCK_REALTIME; + posix_clock_resolution = 1e-3; + } +} + +static inline void +posix_measure (ptimer_system_time *pst) +{ + clock_gettime (posix_clock_id, pst); +} + +static inline double +posix_diff (ptimer_system_time *pst1, ptimer_system_time *pst2) +{ + return ((pst1->tv_sec - pst2->tv_sec) + + (pst1->tv_nsec - pst2->tv_nsec) / 1e9); +} + +static inline double +posix_resolution (void) +{ + return posix_clock_resolution; +} +#endif /* PTIMER_POSIX */ + +#ifdef PTIMER_GETTIMEOFDAY +/* Elapsed time measurement using gettimeofday: system time is held in + struct timeval, retrieved using gettimeofday, and resolution is + unknown. + + This method is used Unix systems without POSIX timers. */ + +typedef struct timeval ptimer_system_time; + +#define IMPL_measure gettimeofday_measure +#define IMPL_diff gettimeofday_diff +#define IMPL_resolution gettimeofday_resolution + +static inline void +gettimeofday_measure (ptimer_system_time *pst) +{ + gettimeofday (pst, NULL); +} + +static inline double +gettimeofday_diff (ptimer_system_time *pst1, ptimer_system_time *pst2) +{ + return ((pst1->tv_sec - pst2->tv_sec) + + (pst1->tv_usec - pst2->tv_usec) / 1e6); +} + +static inline double +gettimeofday_resolution (void) +{ + /* Granularity of gettimeofday varies wildly between architectures. + However, it appears that on modern machines it tends to be better + than 1ms. Assume 100 usecs. */ + return 0.1; +} +#endif /* PTIMER_GETTIMEOFDAY */ + +#ifdef PTIMER_WINDOWS +/* Elapsed time measurement on Windows: where high-resolution timers + are available, time is stored in a LARGE_INTEGER and retrieved + using QueryPerformanceCounter. Otherwise, it is stored in a DWORD + and retrieved using GetTickCount. + + This method is used on Windows. */ + +typedef union { + DWORD lores; /* In case GetTickCount is used */ + LARGE_INTEGER hires; /* In case high-resolution timer is used */ +} ptimer_system_time; + +#define IMPL_init windows_init +#define IMPL_measure windows_measure +#define IMPL_diff windows_diff +#define IMPL_resolution windows_resolution + +/* Whether high-resolution timers are used. Set by ptimer_initialize_once + the first time ptimer_new is called. */ +static bool windows_hires_timers; + +/* Frequency of high-resolution timers -- number of updates per + second. Calculated the first time ptimer_new is called provided + that high-resolution timers are available. */ +static double windows_hires_freq; + +static void +windows_init (void) +{ + LARGE_INTEGER freq; + freq.QuadPart = 0; + QueryPerformanceFrequency (&freq); + if (freq.QuadPart != 0) + { + windows_hires_timers = true; + windows_hires_freq = (double) freq.QuadPart; + } +} + +static inline void +windows_measure (ptimer_system_time *pst) +{ + if (windows_hires_timers) + QueryPerformanceCounter (&pst->hires); + else + /* Where hires counters are not available, use GetTickCount rather + GetSystemTime, because it is unaffected by clock skew and + simpler to use. Note that overflows don't affect us because we + never use absolute values of the ticker, only the + differences. */ + pst->lores = GetTickCount (); +} + +static inline double +windows_diff (ptimer_system_time *pst1, ptimer_system_time *pst2) +{ + if (windows_hires_timers) + return (pst1->hires.QuadPart - pst2->hires.QuadPart) / windows_hires_freq; + else + return pst1->lores - pst2->lores; +} + +static double +windows_resolution (void) +{ + if (windows_hires_timers) + return 1.0 / windows_hires_freq; + else + return 10; /* according to MSDN */ +} +#endif /* PTIMER_WINDOWS */ + +/* The code below this point is independent of timer implementation. */ + +struct ptimer { + /* The starting point in time which, subtracted from the current + time, yields elapsed time. */ + ptimer_system_time start; + + /* The most recent elapsed time, calculated by ptimer_measure(). */ + double elapsed_last; + + /* Approximately, the time elapsed between the true start of the + measurement and the time represented by START. This is used for + adjustment when clock skew is detected. */ + double elapsed_pre_start; +}; + +/* Allocate a new timer and reset it. Return the new timer. */ + +struct ptimer * +ptimer_new (void) +{ + struct ptimer *pt = xnew0 (struct ptimer); +#ifdef IMPL_init + static bool init_done; + if (!init_done) + { + init_done = true; + IMPL_init (); + } +#endif + ptimer_reset (pt); + return pt; +} + +/* Free the resources associated with the timer. Its further use is + prohibited. */ + +void +ptimer_destroy (struct ptimer *pt) +{ + xfree (pt); +} + +/* Reset timer PT. This establishes the starting point from which + ptimer_measure() will return the elapsed time in seconds. It is + allowed to reset a previously used timer. */ + +void +ptimer_reset (struct ptimer *pt) +{ + /* Set the start time to the current time. */ + IMPL_measure (&pt->start); + pt->elapsed_last = 0; + pt->elapsed_pre_start = 0; +} + +/* Measure the elapsed time since timer creation/reset. This causes + the timer to internally call clock_gettime (or gettimeofday, etc.) + to update its idea of current time. The time is returned, but is + also stored for later access through ptimer_read(). + + This function handles clock skew, i.e. time that moves backwards is + ignored. */ + +double +ptimer_measure (struct ptimer *pt) +{ + ptimer_system_time now; + double elapsed; + + IMPL_measure (&now); + elapsed = pt->elapsed_pre_start + IMPL_diff (&now, &pt->start); + + /* Ideally we'd just return the difference between NOW and + pt->start. However, the system timer can be set back, and we + could return a value smaller than when we were last called, even + a negative value. Both of these would confuse the callers, which + expect us to return monotonically nondecreasing values. + + Therefore: if ELAPSED is smaller than its previous known value, + we reset pt->start to the current time and effectively start + measuring from this point. But since we don't want the elapsed + value to start from zero, we set elapsed_pre_start to the last + elapsed time and increment all future calculations by that + amount. + + This cannot happen with Windows and POSIX monotonic/highres + timers, but the check is not expensive. */ + + if (elapsed < pt->elapsed_last) + { + pt->start = now; + pt->elapsed_pre_start = pt->elapsed_last; + elapsed = pt->elapsed_last; + } + + pt->elapsed_last = elapsed; + return elapsed; +} + +/* Return the most recent elapsed time measured with ptimer_measure. + If ptimer_measure has not yet been called since the timer was + created or reset, this returns 0. */ + +double +ptimer_read (const struct ptimer *pt) +{ + return pt->elapsed_last; +} + +/* Return the assessed resolution of the timer implementation, in + seconds. This is used by code that tries to substitute a better + value for timers that have returned zero. */ + +double +ptimer_resolution (void) +{ + return IMPL_resolution (); +} |