sysdeps/generic/fast-jitter.h

   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.  */
  30 static inline uint32_t
  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