1/* Fallback for fast jitter just return 0.
2 Copyright (C) 2019-2023 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19#ifndef _FAST_JITTER_H
20# define _FAST_JITTER_H
21
22# include <stdint.h>
23# include <hp-timing.h>
24
25/* Baseline just return 0. We could create jitter using a clock or
26 'random_bits' but that may imply a syscall and the goal of
27 'get_fast_jitter' is minimal overhead "randomness" when such
28 randomness helps performance. Adding high overhead the function
29 defeats the purpose. */
30static inline uint32_t
31get_fast_jitter (void)
32{
33# if HP_TIMING_INLINE
34 hp_timing_t jitter;
35 HP_TIMING_NOW (jitter);
36 return (uint32_t) jitter;
37# else
38 return 0;
39# endif
40}
41
42#endif
43