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.c

@@ -0,0 +1,42 @@
+/*
+ * 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.
+ */
+
+#include <config.h>
+
+#include "timer.h"
+
+#include "poll-loop.h"
+#include "timeval.h"
+
+/* Returns the number of milliseconds until 'timer' expires. */
+long long int
+timer_msecs_until_expired(const struct timer *timer)
+{
+    switch (timer->t) {
+    case LLONG_MAX: return LLONG_MAX;
+    case LLONG_MIN: return 0;
+    default: return timer->t - time_msec();
+    }
+}
+
+/* Causes poll_block() to wake when 'timer' expires. */
+void
+timer_wait(const struct timer *timer)
+{
+    if (timer->t < LLONG_MAX) {
+        poll_timer_wait_until(timer->t);
+    }
+}