lib: Create new timer library.

Scattered throughout the code base we use long integers to
implement timers.  When the result of timer_msec() is greater than
the time stored, we preform some action.

This commit creates a new timer library intended to replace these
manually managed timers.  Code using the timer library will be more
obviously correct, and more consistent with other code using the
library.

lib/timer.h

@@ -0,0 +1,79 @@
+/*
+ * Copyright (c) 2011 Nicira Networks.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef TIMER_H
+#define TIMER_H 1
+
+#include <stdbool.h>
+
+#include "timeval.h"
+
+struct timer {
+    long long int t;
+};
+
+long long int timer_msecs_until_expired(const struct timer *);
+void timer_wait(const struct timer *);
+
+/* Causes 'timer' to expire when 'duration' milliseconds have passed.
+ *
+ * May be used to initialize 'timer'. */
+static inline void
+timer_set_duration(struct timer *timer, long long int duration)
+{
+    timer->t = time_msec() + duration;
+}
+
+/* Causes 'timer' never to expire.
+ *
+ * May be used to initialize 'timer'. */
+static inline void
+timer_set_infinite(struct timer *timer)
+{
+    timer->t = LLONG_MAX;
+}
+
+/* Causes 'timer' to expire immediately.
+ *
+ * May be used to initialize 'timer'. */
+static inline void
+timer_set_expired(struct timer *timer)
+{
+    timer->t = LLONG_MIN;
+}
+
+/* True if 'timer' had (or will have) expired at 'time'. */
+static inline bool
+timer_expired_at(const struct timer *timer, long long int time)
+{
+    return time >= timer->t;
+}
+
+/* True if 'timer' has expired. */
+static inline bool
+timer_expired(const struct timer *timer)
+{
+    return timer_expired_at(timer, time_msec());
+}
+
+/* Returns ture if 'timer' will never expire. */
+static inline bool
+timer_is_infinite(const struct timer *timer)
+{
+    return timer->t == LLONG_MAX;
+}
+
+#endif /* timer.h */