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e5ac7bd679
ISO C2X adds a timespec_getres function alongside the C11 timespec_get, with functionality similar to that of POSIX clock_getres (including allowing a NULL pointer to be passed to the function). Implement this function for glibc, similarly to the implementation of timespec_get. This includes a basic test like that of timespec_get, but no documentation in the manual, given that TIME_UTC and timespec_get aren't documented in the manual at all. The handling of 64-bit time follows that in timespec_get; people maintaining patch series for 64-bit time will need to update them accordingly (to export __timespec_getres64, redirect calls in time.h and run the test for _TIME_BITS=64). Tested for x86_64 and x86, and (previous version; only testcase differs) with build-many-glibcs.py.
74 lines
2.1 KiB
C
74 lines
2.1 KiB
C
/* clock_getres -- Get the resolution of a POSIX clockid_t.
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Copyright (C) 1999-2021 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library 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 GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <errno.h>
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#include <stdint.h>
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#include <time.h>
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#include <unistd.h>
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#include <sys/param.h>
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#include <libc-internal.h>
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#include <shlib-compat.h>
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static inline int
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realtime_getres (struct timespec *res)
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{
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long int clk_tck = __sysconf (_SC_CLK_TCK);
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if (__glibc_likely (clk_tck != -1))
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{
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/* This implementation assumes that the realtime clock has a
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resolution higher than 1 second. This is the case for any
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reasonable implementation. */
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res->tv_sec = 0;
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res->tv_nsec = 1000000000 / clk_tck;
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return 0;
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}
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return -1;
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}
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/* Get resolution of clock. */
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int
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__clock_getres (clockid_t clock_id, struct timespec *res)
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{
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int retval = -1;
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switch (clock_id)
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{
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case CLOCK_REALTIME:
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retval = realtime_getres (res);
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break;
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default:
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__set_errno (EINVAL);
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break;
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}
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return retval;
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}
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libc_hidden_def (__clock_getres)
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versioned_symbol (libc, __clock_getres, clock_getres, GLIBC_2_17);
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/* clock_getres moved to libc in version 2.17;
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old binaries may expect the symbol version it had in librt. */
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#if SHLIB_COMPAT (libc, GLIBC_2_2, GLIBC_2_17)
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strong_alias (__clock_getres, __clock_getres_2);
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compat_symbol (libc, __clock_getres_2, clock_getres, GLIBC_2_2);
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#endif
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