summaryrefslogtreecommitdiff
path: root/lib/timespec.h
diff options
context:
space:
mode:
Diffstat (limited to 'lib/timespec.h')
-rw-r--r--lib/timespec.h82
1 files changed, 82 insertions, 0 deletions
diff --git a/lib/timespec.h b/lib/timespec.h
new file mode 100644
index 0000000..acf815c
--- /dev/null
+++ b/lib/timespec.h
@@ -0,0 +1,82 @@
+/* timespec -- System time interface
+
+ Copyright (C) 2000, 2002, 2004-2005, 2007, 2009-2011 Free Software
+ Foundation, Inc.
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+#if ! defined TIMESPEC_H
+# define TIMESPEC_H
+
+# include <time.h>
+
+/* Return negative, zero, positive if A < B, A == B, A > B, respectively.
+
+ For each time stamp T, this code assumes that either:
+
+ * T.tv_nsec is in the range 0..999999999; or
+ * T.tv_sec corresponds to a valid leap second on a host that supports
+ leap seconds, and T.tv_nsec is in the range 1000000000..1999999999; or
+ * T.tv_sec is the minimum time_t value and T.tv_nsec is -1; or
+ T.tv_sec is the maximum time_t value and T.tv_nsec is 2000000000.
+ This allows for special struct timespec values that are less or
+ greater than all possible valid time stamps.
+
+ In all these cases, it is safe to subtract two tv_nsec values and
+ convert the result to integer without worrying about overflow on
+ any platform of interest to the GNU project, since all such
+ platforms have 32-bit int or wider.
+
+ Replacing "(int) (a.tv_nsec - b.tv_nsec)" with something like
+ "a.tv_nsec < b.tv_nsec ? -1 : a.tv_nsec > b.tv_nsec" would cause
+ this function to work in some cases where the above assumption is
+ violated, but not in all cases (e.g., a.tv_sec==1, a.tv_nsec==-2,
+ b.tv_sec==0, b.tv_nsec==999999999) and is arguably not worth the
+ extra instructions. Using a subtraction has the advantage of
+ detecting some invalid cases on platforms that detect integer
+ overflow.
+
+ The (int) cast avoids a gcc -Wconversion warning. */
+
+static inline int
+timespec_cmp (struct timespec a, struct timespec b)
+{
+ return (a.tv_sec < b.tv_sec ? -1
+ : a.tv_sec > b.tv_sec ? 1
+ : (int) (a.tv_nsec - b.tv_nsec));
+}
+
+/* Return -1, 0, 1, depending on the sign of A. A.tv_nsec must be
+ nonnegative. */
+static inline int
+timespec_sign (struct timespec a)
+{
+ return a.tv_sec < 0 ? -1 : a.tv_sec || a.tv_nsec;
+}
+
+struct timespec timespec_add (struct timespec, struct timespec);
+struct timespec timespec_sub (struct timespec, struct timespec);
+struct timespec dtotimespec (double);
+
+/* Return an approximation to A, of type 'double'. */
+static inline double
+timespectod (struct timespec a)
+{
+ return a.tv_sec + a.tv_nsec / 1e9;
+}
+
+void gettime (struct timespec *);
+int settime (struct timespec const *);
+
+#endif