1 files changed, 59 insertions, 0 deletions
diff --git a/statistics/src/main/java/com/yahoo/statistics/SampleDirectory.java b/statistics/src/main/java/com/yahoo/statistics/SampleDirectory.java
new file mode 100644
index 00000000000..c920c35ca13
--- /dev/null
+++ b/statistics/src/main/java/com/yahoo/statistics/SampleDirectory.java
@@ -0,0 +1,59 @@
+// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.statistics;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import com.yahoo.statistics.SampleSet.Sampling;
+
+/**
+ * Book-keeping class to know which SampleSet instances have unlogged data.
+ *
+ * @author <a href="mailto:steinar@yahoo-inc.com">Steinar Knutsen</a>
+ */
+final class SampleDirectory {
+    private final Object directoryLock = new Object();
+    private List<SampleSet> directory = new ArrayList<>(200);
+
+    void put(SampleSet s) {
+        synchronized (directoryLock) {
+            directory.add(s);
+            s.setRegisteredForLogging(true);
+        }
+    }
+
+    /**
+     * Get a view of the current generation of data and instantiate a new
+     * generation. This does the memory barrier two-step for the
+     * client.
+     */
+    Sampling[] fetchValues() {
+        Sampling[] copyToReturn;
+        synchronized (directoryLock) {
+            List<SampleSet> tmpDir = directory;
+            copyToReturn = new Sampling[tmpDir.size()];
+            List<SampleSet> newDir = new ArrayList<>(200);
+            for (int i = 0; i < copyToReturn.length; ++i) {
+                copyToReturn[i] = tmpDir.get(i).getAndReset();
+            }
+            directory = newDir;
+        }
+        return copyToReturn;
+    }
+
+    /**
+     * Return a view of the current generation of data. This does the memory
+     * barrier two-step for the client.
+     */
+    Sampling[] viewValues() {
+        Sampling[] copy;
+        synchronized (directoryLock) {
+            copy = new Sampling[directory.size()];
+            for (int i = 0; i < copy.length; ++i) {
+                copy[i] = directory.get(i).values;
+            }
+        }
+        return copy;
+    }
+
+}