1 /* timespec -- System time interface 2 3 Copyright (C) 2000, 2002, 2004-2005, 2007, 2009-2011 Free Software 4 Foundation, Inc. 5 6 This program is free software: you can redistribute it and/or modify 7 it under the terms of the GNU General Public License as published by 8 the Free Software Foundation; either version 3 of the License, or 9 (at your option) any later version. 10 11 This program is distributed in the hope that it will be useful, 12 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 GNU General Public License for more details. 15 16 You should have received a copy of the GNU General Public License 17 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 18 19 #if ! defined TIMESPEC_H 20 # define TIMESPEC_H 21 22 # include <time.h> 23 24 /* Return negative, zero, positive if A < B, A == B, A > B, respectively. 25 26 For each time stamp T, this code assumes that either: 27 28 * T.tv_nsec is in the range 0..999999999; or 29 * T.tv_sec corresponds to a valid leap second on a host that supports 30 leap seconds, and T.tv_nsec is in the range 1000000000..1999999999; or 31 * T.tv_sec is the minimum time_t value and T.tv_nsec is -1; or 32 T.tv_sec is the maximum time_t value and T.tv_nsec is 2000000000. 33 This allows for special struct timespec values that are less or 34 greater than all possible valid time stamps. 35 36 In all these cases, it is safe to subtract two tv_nsec values and 37 convert the result to integer without worrying about overflow on 38 any platform of interest to the GNU project, since all such 39 platforms have 32-bit int or wider. 40 41 Replacing "(int) (a.tv_nsec - b.tv_nsec)" with something like 42 "a.tv_nsec < b.tv_nsec ? -1 : a.tv_nsec > b.tv_nsec" would cause 43 this function to work in some cases where the above assumption is 44 violated, but not in all cases (e.g., a.tv_sec==1, a.tv_nsec==-2, 45 b.tv_sec==0, b.tv_nsec==999999999) and is arguably not worth the 46 extra instructions. Using a subtraction has the advantage of 47 detecting some invalid cases on platforms that detect integer 48 overflow. 49 50 The (int) cast avoids a gcc -Wconversion warning. */ 51 52 static inline int 53 timespec_cmp (struct timespec a, struct timespec b) 54 { 55 return (a.tv_sec < b.tv_sec ? -1 56 : a.tv_sec > b.tv_sec ? 1 57 : (int) (a.tv_nsec - b.tv_nsec)); 58 } 59 60 /* Return -1, 0, 1, depending on the sign of A. A.tv_nsec must be 61 nonnegative. */ 62 static inline int 63 timespec_sign (struct timespec a) 64 { 65 return a.tv_sec < 0 ? -1 : a.tv_sec || a.tv_nsec; 66 } 67 68 struct timespec timespec_add (struct timespec, struct timespec); 69 struct timespec timespec_sub (struct timespec, struct timespec); 70 struct timespec dtotimespec (double); 71 72 /* Return an approximation to A, of type 'double'. */ 73 static inline double 74 timespectod (struct timespec a) 75 { 76 return a.tv_sec + a.tv_nsec / 1e9; 77 } 78 79 void gettime (struct timespec *); 80 int settime (struct timespec const *); 81 82 #endif 83