Directory Restructure (#1163)

* Move tests -> testing

* Directory restructure

* Update Cargo.toml during restructure

* Update Makefile during restructure

* Fix arbitrary path

common/slot_clock/src/lib.rs

@@ -0,0 +1,60 @@
+#[macro_use]
+extern crate lazy_static;
+
+mod manual_slot_clock;
+mod metrics;
+mod system_time_slot_clock;
+
+use std::time::Duration;
+
+pub use crate::manual_slot_clock::ManualSlotClock;
+pub use crate::manual_slot_clock::ManualSlotClock as TestingSlotClock;
+pub use crate::system_time_slot_clock::SystemTimeSlotClock;
+pub use metrics::scrape_for_metrics;
+pub use types::Slot;
+
+/// A clock that reports the current slot.
+///
+/// The clock is not required to be monotonically increasing and may go backwards.
+pub trait SlotClock: Send + Sync + Sized {
+    /// Creates a new slot clock where the first slot is `genesis_slot`, genesis occurred
+    /// `genesis_duration` after the `UNIX_EPOCH` and each slot is `slot_duration` apart.
+    fn new(genesis_slot: Slot, genesis_duration: Duration, slot_duration: Duration) -> Self;
+
+    /// Returns the slot at this present time.
+    fn now(&self) -> Option<Slot>;
+
+    /// Returns the present time as a duration since the UNIX epoch.
+    ///
+    /// Returns `None` if the present time is before the UNIX epoch (unlikely).
+    fn now_duration(&self) -> Option<Duration>;
+
+    /// Returns the slot of the given duration since the UNIX epoch.
+    fn slot_of(&self, now: Duration) -> Option<Slot>;
+
+    /// Returns the duration between slots
+    fn slot_duration(&self) -> Duration;
+
+    /// Returns the duration from now until `slot`.
+    fn duration_to_slot(&self, slot: Slot) -> Option<Duration>;
+
+    /// Returns the duration until the next slot.
+    fn duration_to_next_slot(&self) -> Option<Duration>;
+
+    /// Returns the duration until the first slot of the next epoch.
+    fn duration_to_next_epoch(&self, slots_per_epoch: u64) -> Option<Duration>;
+
+    /// Returns the first slot to be returned at the genesis time.
+    fn genesis_slot(&self) -> Slot;
+
+    /// Returns the slot if the internal clock were advanced by `duration`.
+    fn now_with_future_tolerance(&self, tolerance: Duration) -> Option<Slot> {
+        self.slot_of(self.now_duration()?.checked_add(tolerance)?)
+    }
+
+    /// Returns the slot if the internal clock were reversed by `duration`.
+    fn now_with_past_tolerance(&self, tolerance: Duration) -> Option<Slot> {
+        self.slot_of(self.now_duration()?.checked_sub(tolerance)?)
+            .or_else(|| Some(self.genesis_slot()))
+    }
+}