From d4de68cc71b66866b763dd356783e49edd893909 Mon Sep 17 00:00:00 2001
From: Diego <diegolparra@gmail.com>
Date: Wed, 3 Dec 2014 21:31:46 -0300
Subject: + core: introduce Sequencer to generate a incrementing sequence of
 Longs with a simple Long overflow protection

---
 .../main/scala/kamon/util/PaddedAtomicLong.scala   |  3 +-
 .../src/main/scala/kamon/util/Sequencer.scala      | 40 ++++++++++++++++++++++
 2 files changed, 42 insertions(+), 1 deletion(-)
 create mode 100644 kamon-core/src/main/scala/kamon/util/Sequencer.scala

(limited to 'kamon-core/src/main/scala/kamon/util')

diff --git a/kamon-core/src/main/scala/kamon/util/PaddedAtomicLong.scala b/kamon-core/src/main/scala/kamon/util/PaddedAtomicLong.scala
index 9c926372..9019eb4c 100644
--- a/kamon-core/src/main/scala/kamon/util/PaddedAtomicLong.scala
+++ b/kamon-core/src/main/scala/kamon/util/PaddedAtomicLong.scala
@@ -1,4 +1,3 @@
-package kamon.util
 /*
  * =========================================================================================
  * Copyright © 2013-2014 the kamon project <http://kamon.io/>
@@ -15,6 +14,8 @@ package kamon.util
  * =========================================================================================
  */
 
+package kamon.util
+
 import java.util.concurrent.atomic.AtomicLong
 
 class PaddedAtomicLong(value: Long = 0) extends AtomicLong(value) {
diff --git a/kamon-core/src/main/scala/kamon/util/Sequencer.scala b/kamon-core/src/main/scala/kamon/util/Sequencer.scala
new file mode 100644
index 00000000..8901ba81
--- /dev/null
+++ b/kamon-core/src/main/scala/kamon/util/Sequencer.scala
@@ -0,0 +1,40 @@
+/*
+ * =========================================================================================
+ * 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.util
+
+/**
+ * This class implements an extremely efficient, thread-safe way to generate a
+ * simple incrementing sequence of Longs with a simple Long overflow protection.
+ */
+class Sequencer {
+  private val CloseToOverflow = Long.MaxValue - 1000000000
+  private val sequenceNumber = new PaddedAtomicLong(1L)
+
+  def next(): Long = {
+    val current = sequenceNumber.getAndIncrement
+
+    // check if this value is getting close to overflow?
+    if (current > CloseToOverflow) {
+      sequenceNumber.set(current - CloseToOverflow) // we need maintain the order
+    }
+    current
+  }
+}
+
+object Sequencer {
+  def apply(): Sequencer = new Sequencer()
+}
\ No newline at end of file
-- 
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