Move common clock implementation helpers

This change fixes the dependencies between the clock implementation headers. All
the clocks share the common clock offset, but are otherwise independent (though
the `db_clock` does depend on `gc_clock` for time point conversions).

clocks-impl.cc

@@ -19,6 +19,6 @@
  * along with Scylla.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include "gc_clock.hh"
+#include "clocks-impl.hh"
 
 std::atomic<int64_t> clocks_offset;

clocks-impl.hh

@@ -0,0 +1,49 @@
+/*
+ * Copyright (C) 2017 ScyllaDB
+ */
+
+/*
+ * This file is part of Scylla.
+ *
+ * Scylla is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Scylla 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 Scylla.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <algorithm>
+#include <atomic>
+#include <chrono>
+#include <cstdint>
+
+extern std::atomic<int64_t> clocks_offset;
+
+template<typename Duration>
+static inline void forward_jump_clocks(Duration delta)
+{
+    auto d = std::chrono::duration_cast<std::chrono::seconds>(delta).count();
+    clocks_offset.fetch_add(d, std::memory_order_relaxed);
+}
+
+static inline std::chrono::seconds get_clocks_offset()
+{
+    auto off = clocks_offset.load(std::memory_order_relaxed);
+    return std::chrono::seconds(off);
+}
+
+// Returns a time point which is earlier from t by d, or minimum time point if it cannot be represented.
+template<typename Clock, typename Duration, typename Rep, typename Period>
+inline
+auto saturating_subtract(std::chrono::time_point<Clock, Duration> t, std::chrono::duration<Rep, Period> d) -> decltype(t) {
+    return std::max(t, decltype(t)::min() + d) - d;
+}

configure.py

@@ -497,7 +497,7 @@ scylla_core = (['database.cc',
                  'streaming/stream_manager.cc',
                  'streaming/stream_result_future.cc',
                  'streaming/stream_session_state.cc',
-                 'gc_clock.cc',
+                 'clocks-impl.cc',
                  'partition_slice_builder.cc',
                  'init.cc',
                  'lister.cc',

db_clock.hh

@@ -21,6 +21,7 @@
 
 #pragma once
 
+#include "clocks-impl.hh"
 #include "gc_clock.hh"
 
 #include <chrono>

gc_clock.hh

@@ -21,20 +21,13 @@
 
 #pragma once
 
+#include "clocks-impl.hh"
+
 #include <seastar/core/lowres_clock.hh>
 
-#include <atomic>
 #include <chrono>
 #include <experimental/optional>
 
-extern std::atomic<int64_t> clocks_offset;
-
-static inline std::chrono::seconds get_clocks_offset()
-{
-    auto off = clocks_offset.load(std::memory_order_relaxed);
-    return std::chrono::seconds(off);
-}
-
 // FIXME: wraps around in 2038
 class gc_clock {
 public:
@@ -59,22 +52,8 @@ public:
     }
 };
 
-// Returns a time point which is earlier from t by d, or minimum time point if it cannot be represented.
-template<typename Clock, typename Duration, typename Rep, typename Period>
-inline
-auto saturating_subtract(std::chrono::time_point<Clock, Duration> t, std::chrono::duration<Rep, Period> d) -> decltype(t) {
-    return std::max(t, decltype(t)::min() + d) - d;
-}
-
 using expiry_opt = std::experimental::optional<gc_clock::time_point>;
 using ttl_opt = std::experimental::optional<gc_clock::duration>;
 
 // 20 years in seconds
 static constexpr gc_clock::duration max_ttl = gc_clock::duration{20 * 365 * 24 * 60 * 60};
-
-template<typename Duration>
-static inline void forward_jump_clocks(Duration delta)
-{
-    auto d = std::chrono::duration_cast<std::chrono::seconds>(delta).count();
-    clocks_offset.fetch_add(d, std::memory_order_relaxed);
-}

timestamp.hh

@@ -24,7 +24,7 @@
 #include <cstdint>
 #include <limits>
 #include <chrono>
-#include "db_clock.hh"
+#include "clocks-impl.hh"
 
 namespace api {