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137 lines
4.3 KiB
C
137 lines
4.3 KiB
C
/* timespec -- System time interface
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Copyright (C) 2000, 2002, 2004-2005, 2007, 2009-2020 Free Software
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Foundation, Inc.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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#if ! defined TIMESPEC_H
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#define TIMESPEC_H
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#include <time.h>
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#ifndef _GL_INLINE_HEADER_BEGIN
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#error "Please include config.h first."
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#endif
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_GL_INLINE_HEADER_BEGIN
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#ifndef _GL_TIMESPEC_INLINE
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# define _GL_TIMESPEC_INLINE _GL_INLINE
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#endif
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#ifdef __cplusplus
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extern "C" {
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#endif
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#include "arg-nonnull.h"
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#include "verify.h"
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/* Inverse resolution of timespec timestamps (in units per second),
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and log base 10 of the inverse resolution. */
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enum { TIMESPEC_HZ = 1000000000 };
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enum { LOG10_TIMESPEC_HZ = 9 };
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/* Obsolescent names for backward compatibility.
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They are misnomers, because TIMESPEC_RESOLUTION is not a resolution. */
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enum { TIMESPEC_RESOLUTION = TIMESPEC_HZ };
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enum { LOG10_TIMESPEC_RESOLUTION = LOG10_TIMESPEC_HZ };
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/* Return a timespec with seconds S and nanoseconds NS. */
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_GL_TIMESPEC_INLINE struct timespec
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make_timespec (time_t s, long int ns)
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{
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struct timespec r;
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r.tv_sec = s;
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r.tv_nsec = ns;
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return r;
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}
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/* Return negative, zero, positive if A < B, A == B, A > B, respectively.
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For each timestamp T, this code assumes that either:
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* T.tv_nsec is in the range 0..999999999; or
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* T.tv_sec corresponds to a valid leap second on a host that supports
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leap seconds, and T.tv_nsec is in the range 1000000000..1999999999; or
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* T.tv_sec is the minimum time_t value and T.tv_nsec is -1; or
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T.tv_sec is the maximum time_t value and T.tv_nsec is 2000000000.
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This allows for special struct timespec values that are less or
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greater than all possible valid timestamps.
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In all these cases, it is safe to subtract two tv_nsec values and
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convert the result to integer without worrying about overflow on
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any platform of interest to the GNU project, since all such
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platforms have 32-bit int or wider.
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Replacing "a.tv_nsec - b.tv_nsec" with something like
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"a.tv_nsec < b.tv_nsec ? -1 : a.tv_nsec > b.tv_nsec" would cause
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this function to work in some cases where the above assumption is
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violated, but not in all cases (e.g., a.tv_sec==1, a.tv_nsec==-2,
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b.tv_sec==0, b.tv_nsec==999999999) and is arguably not worth the
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extra instructions. Using a subtraction has the advantage of
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detecting some invalid cases on platforms that detect integer
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overflow. */
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_GL_TIMESPEC_INLINE int _GL_ATTRIBUTE_PURE
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timespec_cmp (struct timespec a, struct timespec b)
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{
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if (a.tv_sec < b.tv_sec)
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return -1;
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if (a.tv_sec > b.tv_sec)
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return 1;
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/* Pacify gcc -Wstrict-overflow (bleeding-edge circa 2017-10-02). See:
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https://lists.gnu.org/r/bug-gnulib/2017-10/msg00006.html */
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assume (-1 <= a.tv_nsec && a.tv_nsec <= 2 * TIMESPEC_HZ);
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assume (-1 <= b.tv_nsec && b.tv_nsec <= 2 * TIMESPEC_HZ);
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return a.tv_nsec - b.tv_nsec;
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}
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/* Return -1, 0, 1, depending on the sign of A. A.tv_nsec must be
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nonnegative. */
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_GL_TIMESPEC_INLINE int _GL_ATTRIBUTE_PURE
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timespec_sign (struct timespec a)
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{
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return a.tv_sec < 0 ? -1 : a.tv_sec || a.tv_nsec;
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}
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struct timespec timespec_add (struct timespec, struct timespec)
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_GL_ATTRIBUTE_CONST;
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struct timespec timespec_sub (struct timespec, struct timespec)
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_GL_ATTRIBUTE_CONST;
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struct timespec dtotimespec (double)
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_GL_ATTRIBUTE_CONST;
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/* Return an approximation to A, of type 'double'. */
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_GL_TIMESPEC_INLINE double
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timespectod (struct timespec a)
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{
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return a.tv_sec + a.tv_nsec / 1e9;
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}
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struct timespec current_timespec (void);
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void gettime (struct timespec *) _GL_ARG_NONNULL ((1));
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int settime (struct timespec const *) _GL_ARG_NONNULL ((1));
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#ifdef __cplusplus
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}
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#endif
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_GL_INLINE_HEADER_END
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#endif
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