1 files changed, 59 insertions, 0 deletions
diff --git a/kamon-core/src/main/scala/kamon/metric/instrument/Counter.scala b/kamon-core/src/main/scala/kamon/metric/instrument/Counter.scala
new file mode 100644
index 00000000..b592bcd3
--- /dev/null
+++ b/kamon-core/src/main/scala/kamon/metric/instrument/Counter.scala
@@ -0,0 +1,59 @@
+/*
+ * =========================================================================================
+ * Copyright © 2013-2014 the kamon project <http://kamon.io/>
+ *
+ * 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.
+ * =========================================================================================
+ */
+
+package kamon.metric.instrument
+
+import jsr166e.LongAdder
+import kamon.metric.{ CollectionContext, MetricSnapshot, MetricRecorder }
+
+trait Counter extends MetricRecorder {
+  type SnapshotType = Counter.Snapshot
+
+  def increment(): Unit
+  def increment(times: Long): Unit
+}
+
+object Counter {
+
+  def apply(): Counter = new LongAdderCounter
+
+  trait Snapshot extends MetricSnapshot {
+    type SnapshotType = Counter.Snapshot
+
+    def count: Long
+    def merge(that: Counter.Snapshot, context: CollectionContext): Counter.Snapshot
+  }
+}
+
+class LongAdderCounter extends Counter {
+  private val counter = new LongAdder
+
+  def increment(): Unit = counter.increment()
+
+  def increment(times: Long): Unit = {
+    if (times < 0)
+      throw new UnsupportedOperationException("Counters cannot be decremented")
+    counter.add(times)
+  }
+
+  def collect(context: CollectionContext): Counter.Snapshot = CounterSnapshot(counter.sumThenReset())
+
+  def cleanup: Unit = {}
+}
+
+case class CounterSnapshot(count: Long) extends Counter.Snapshot {
+  def merge(that: Counter.Snapshot, context: CollectionContext): Counter.Snapshot = CounterSnapshot(count + that.count)
+}
+\ No newline at end of file