1 /* Fallback for fast jitter just return 0.
2 Copyright (C) 2019-2022 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. */
30 static inline uint32_t
get_fast_jitter(void)31 get_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