| 1 | /* clock_getres -- Get the resolution of a POSIX clockid_t. |
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| 2 | Copyright (C) 1999-2022 Free Software Foundation, Inc. |
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| 3 | This file is part of the GNU C Library. |
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| 4 | |
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| 5 | The GNU C Library is free software; you can redistribute it and/or |
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| 6 | modify it under the terms of the GNU Lesser General Public |
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| 7 | License as published by the Free Software Foundation; either |
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| 8 | version 2.1 of the License, or (at your option) any later version. |
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| 9 | |
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| 10 | The GNU C Library is distributed in the hope that it will be useful, |
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| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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| 13 | Lesser General Public License for more details. |
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| 14 | |
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| 15 | You should have received a copy of the GNU Lesser General Public |
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| 16 | License along with the GNU C Library; if not, see |
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| 17 | <https://www.gnu.org/licenses/>. */ |
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| 18 | |
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| 19 | #include <errno.h> |
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| 20 | #include <stdint.h> |
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| 21 | #include <time.h> |
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| 22 | #include <unistd.h> |
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| 23 | #include <sys/param.h> |
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| 24 | #include <libc-internal.h> |
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| 25 | #include <shlib-compat.h> |
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| 26 | |
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| 27 | static inline int |
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| 28 | realtime_getres (struct timespec *res) |
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| 29 | { |
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| 30 | long int clk_tck = __sysconf (_SC_CLK_TCK); |
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| 31 | |
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| 32 | if (__glibc_likely (clk_tck != -1)) |
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| 33 | { |
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| 34 | /* This implementation assumes that the realtime clock has a |
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| 35 | resolution higher than 1 second. This is the case for any |
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| 36 | reasonable implementation. */ |
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| 37 | if (res) |
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| 38 | { |
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| 39 | res->tv_sec = 0; |
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| 40 | res->tv_nsec = 1000000000 / clk_tck; |
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| 41 | } |
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| 42 | return 0; |
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| 43 | } |
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| 44 | |
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| 45 | return -1; |
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| 46 | } |
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| 47 | |
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| 48 | |
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| 49 | /* Get resolution of clock. */ |
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| 50 | int |
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| 51 | __clock_getres (clockid_t clock_id, struct timespec *res) |
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| 52 | { |
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| 53 | int retval = -1; |
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| 54 | |
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| 55 | switch (clock_id) |
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| 56 | { |
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| 57 | case CLOCK_REALTIME: |
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| 58 | retval = realtime_getres (res); |
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| 59 | break; |
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| 60 | |
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| 61 | default: |
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| 62 | __set_errno (EINVAL); |
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| 63 | break; |
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| 64 | } |
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| 65 | |
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| 66 | return retval; |
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| 67 | } |
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| 68 | libc_hidden_def (__clock_getres) |
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| 69 | |
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| 70 | versioned_symbol (libc, __clock_getres, clock_getres, GLIBC_2_17); |
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| 71 | /* clock_getres moved to libc in version 2.17; |
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| 72 | old binaries may expect the symbol version it had in librt. */ |
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| 73 | #if SHLIB_COMPAT (libc, GLIBC_2_2, GLIBC_2_17) |
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| 74 | strong_alias (__clock_getres, __clock_getres_2); |
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| 75 | compat_symbol (libc, __clock_getres_2, clock_getres, GLIBC_2_2); |
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| 76 | #endif |
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| 77 | |
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