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sourceware.org Git - glibc.git/blob - sysdeps/unix/clock_gettime.c
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1 /* Copyright (C) 1999, 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, write to the Free
16 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
23 #include <libc-internal.h>
28 /* Clock frequency of the processor. We make it a 64-bit variable
29 because some jokers are already playing with processors with more
31 static hp_timing_t freq
;
34 /* This function is defined in the thread library. */
35 extern int __pthread_clock_gettime (clockid_t clock_id
, hp_timing_t freq
,
37 __attribute__ ((__weak__
));
41 /* Get current value of CLOCK and store it in TP. */
43 clock_gettime (clockid_t clock_id
, struct timespec
*tp
)
49 #define HANDLE_REALTIME \
52 retval = gettimeofday (&tv, NULL); \
54 /* Convert into `timespec'. */ \
55 TIMEVAL_TO_TIMESPEC (&tv, tp); \
62 #ifndef HANDLED_REALTIME
70 if ((clock_id
& ((1 << CLOCK_IDFIELD_SIZE
) - 1))
71 != CLOCK_THREAD_CPUTIME_ID
)
80 case CLOCK_PROCESS_CPUTIME_ID
:
84 if (__builtin_expect (freq
== 0, 0))
86 /* This can only happen if we haven't initialized the `freq'
87 variable yet. Do this now. We don't have to protect this
88 code against multiple execution since all of them should
89 lead to the same result. */
90 freq
= __get_clockfreq ();
91 if (__builtin_expect (freq
== 0, 0))
92 /* Something went wrong. */
96 if (clock_id
!= CLOCK_PROCESS_CPUTIME_ID
97 && __pthread_clock_gettime
!= NULL
)
99 retval
= __pthread_clock_gettime (clock_id
, freq
, tp
);
103 /* Get the current counter. */
106 /* Compute the offset since the start time of the process. */
107 tsc
-= GL(dl_cpuclock_offset
);
109 /* Compute the seconds. */
110 tp
->tv_sec
= tsc
/ freq
;
112 /* And the nanoseconds. This computation should be stable until
113 we get machines with about 16GHz frequency. */
114 tp
->tv_nsec
= ((tsc
% freq
) * UINT64_C (1000000000)) / freq
;
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