[PATCH] time: basic utility for getting the system time

[PATCH] time: basic utility for getting the system time

[James Prestwood]

[-- Attachment #1: Type: text/plain, Size: 5590 bytes --]

Timeouts are sometimes overkill for long timeouts, or timeouts that
don't require being immediately serviced once expired. For this
reason the 'time' module was added which allows you to get the system
clock time, as well as some basic APIs to check if two time values are
before/after one another, and for calculating an offset from a start
time. This allows an application to handle its own timeouts lazily
with no tie to the main loop.

The APIs were modeled after the kernel APIs in jiffies.h
---
 Makefile.am |  6 ++--
 ell/ell.sym |  6 ++++
 ell/time.c  | 93 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 ell/time.h  | 45 ++++++++++++++++++++++++++
 4 files changed, 148 insertions(+), 2 deletions(-)
 create mode 100644 ell/time.c
 create mode 100644 ell/time.h

diff --git a/Makefile.am b/Makefile.am
index 3eecbe0..1c089ec 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -51,7 +51,8 @@ pkginclude_HEADERS = ell/ell.h \
 			ell/dhcp.h \
 			ell/cert.h \
 			ell/ecc.h \
-			ell/ecdh.h
+			ell/ecdh.h \
+			ell/time.h
 
 lib_LTLIBRARIES = ell/libell.la
 
@@ -121,7 +122,8 @@ ell_libell_la_SOURCES = $(linux_headers) \
 			ell/ecc.h \
 			ell/ecc-external.c \
 			ell/ecc.c \
-			ell/ecdh.c
+			ell/ecdh.c \
+			ell/time.c
 
 ell_libell_la_LDFLAGS = -no-undefined \
 			-Wl,--version-script=$(top_srcdir)/ell/ell.sym \
diff --git a/ell/ell.sym b/ell/ell.sym
index 7643a25..e67716e 100644
--- a/ell/ell.sym
+++ b/ell/ell.sym
@@ -485,6 +485,12 @@ global:
 	/* ecdh */
 	l_ecdh_generate_key_pair;
 	l_ecdh_generate_shared_secret;
+
+	/* time */
+	l_time_now;
+	l_time_after;
+	l_time_before;
+	l_time_offset;
 local:
 	*;
 };
diff --git a/ell/time.c b/ell/time.c
new file mode 100644
index 0000000..3c2b929
--- /dev/null
+++ b/ell/time.c
@@ -0,0 +1,93 @@
+/*
+ *
+ *  Embedded Linux library
+ *
+ *  Copyright (C) 2019  Intel Corporation. All rights reserved.
+ *
+ *  This library is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU Lesser General Public
+ *  License as published by the Free Software Foundation; either
+ *  version 2.1 of the License, or (at your option) any later version.
+ *
+ *  This library 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
+ *  Lesser General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Lesser General Public
+ *  License along with this library; if not, write to the Free Software
+ *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <time.h>
+#include <limits.h>
+
+#include "time.h"
+#include "private.h"
+
+/**
+ * l_time_now:
+ *
+ * Get the running clocktime in microseconds
+ *
+ * Returns: Current clock time in microseconds
+ **/
+LIB_EXPORT uint64_t l_time_now(void)
+{
+	struct timespec now;
+
+	clock_gettime(CLOCK_BOOTTIME, &now);
+
+	return now.tv_sec * 1000000 + now.tv_nsec / 1000;
+}
+
+/**
+ * l_time_after
+ *
+ * Returns: True if time a is after time b
+ **/
+LIB_EXPORT bool l_time_after(uint64_t a, uint64_t b)
+{
+	if ((int64_t)(b - a) < 0)
+		return true;
+
+	return false;
+}
+
+/**
+ * l_time_before
+ *
+ * Returns: True if time a is before time b
+ **/
+LIB_EXPORT bool l_time_before(uint64_t a, uint64_t b)
+{
+	return l_time_after(b, a);
+}
+
+/**
+ * l_time_offset
+ *
+ * @time: Start time to calculate offset
+ * @offset: Amount of time to add to 'time'
+ *
+ * Adds an offset to a time value. This checks for overflow, and if detected
+ * returns ULONG_MAX.
+ *
+ * Returns: A time value 'time' + 'offset'. Or ULONG_MAX if time + offset
+ * exceeds ULONG_MAX.
+ **/
+LIB_EXPORT uint64_t l_time_offset(uint64_t time, uint64_t offset)
+{
+	uint64_t added = time + offset;
+
+	/* check overflow */
+	if (!l_time_after(added, time))
+		return ULONG_MAX;
+
+	return added;
+}
diff --git a/ell/time.h b/ell/time.h
new file mode 100644
index 0000000..00c09cd
--- /dev/null
+++ b/ell/time.h
@@ -0,0 +1,45 @@
+/*
+ *
+ *  Embedded Linux library
+ *
+ *  Copyright (C) 2019  Intel Corporation. All rights reserved.
+ *
+ *  This library is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU Lesser General Public
+ *  License as published by the Free Software Foundation; either
+ *  version 2.1 of the License, or (at your option) any later version.
+ *
+ *  This library 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
+ *  Lesser General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Lesser General Public
+ *  License along with this library; if not, write to the Free Software
+ *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ */
+
+#ifndef __ELL_TIME_H
+#define __ELL_TIME_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdint.h>
+#include <stdbool.h>
+
+uint64_t l_time_now(void);
+
+bool l_time_after(uint64_t a, uint64_t b);
+
+bool l_time_before(uint64_t a, uint64_t b);
+
+uint64_t l_time_offset(uint64_t time, uint64_t offset);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __ELL_TIME_H */
-- 
2.17.1