| | 1 | /* |
| | 2 | * Copyright (c) 2016 Apple Inc. All rights reserved. |
| | 3 | * |
| | 4 | * @APPLE_LICENSE_HEADER_START@ |
| | 5 | * |
| | 6 | * This file contains Original Code and/or Modifications of Original Code |
| | 7 | * as defined in and that are subject to the Apple Public Source License |
| | 8 | * Version 2.0 (the 'License'). You may not use this file except in |
| | 9 | * compliance with the License. Please obtain a copy of the License at |
| | 10 | * http://www.opensource.apple.com/apsl/ and read it before using this |
| | 11 | * file. |
| | 12 | * |
| | 13 | * The Original Code and all software distributed under the License are |
| | 14 | * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER |
| | 15 | * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, |
| | 16 | * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, |
| | 17 | * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. |
| | 18 | * Please see the License for the specific language governing rights and |
| | 19 | * limitations under the License. |
| | 20 | * |
| | 21 | * @APPLE_LICENSE_HEADER_END@ |
| | 22 | */ |
| | 23 | #include <mach/mach_time.h> |
| | 24 | |
| | 25 | extern kern_return_t |
| | 26 | mach_timebase_info_trap(mach_timebase_info_t info); |
| | 27 | |
| | 28 | kern_return_t |
| | 29 | mach_timebase_info(mach_timebase_info_t info) |
| | 30 | { |
| | 31 | static mach_timebase_info_data_t cached_info; |
| | 32 | |
| | 33 | /* |
| | 34 | * This is racy, but because it is safe to initialize twice we avoid a |
| | 35 | * barrier in the fast path by risking double initialization. |
| | 36 | */ |
| | 37 | if (cached_info.numer == 0 || cached_info.denom == 0) { |
| | 38 | kern_return_t kr = mach_timebase_info_trap(&cached_info); |
| | 39 | if (kr != KERN_SUCCESS) { |
| | 40 | return kr; |
| | 41 | } |
| | 42 | } |
| | 43 | |
| | 44 | info->numer = cached_info.numer; |
| | 45 | info->denom = cached_info.denom; |
| | 46 | |
| | 47 | return KERN_SUCCESS; |
| | 48 | } |
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