| 1 | /* Fallback for fast jitter just return 0. |
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| 2 | Copyright (C) 2019-2022 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 | #ifndef _FAST_JITTER_H |
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| 20 | # define _FAST_JITTER_H |
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| 21 | |
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| 22 | # include <stdint.h> |
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| 23 | # include <hp-timing.h> |
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| 24 | |
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| 25 | /* Baseline just return 0. We could create jitter using a clock or |
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| 26 | 'random_bits' but that may imply a syscall and the goal of |
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| 27 | 'get_fast_jitter' is minimal overhead "randomness" when such |
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| 28 | randomness helps performance. Adding high overhead the function |
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| 29 | defeats the purpose. */ |
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| 30 | static inline uint32_t |
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| 31 | get_fast_jitter (void) |
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| 32 | { |
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| 33 | # if HP_TIMING_INLINE |
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| 34 | hp_timing_t jitter; |
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| 35 | HP_TIMING_NOW (jitter); |
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| 36 | return (uint32_t) jitter; |
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| 37 | # else |
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| 38 | return 0; |
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| 39 | # endif |
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| 40 | } |
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| 41 | |
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| 42 | #endif |
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| 43 | |
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