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1 files changed, 103 insertions, 0 deletions

diff --git a/vespajlib/src/test/java/com/yahoo/concurrent/ThreadRobustListTestCase.java b/vespajlib/src/test/java/com/yahoo/concurrent/ThreadRobustListTestCase.java
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+++ b/vespajlib/src/test/java/com/yahoo/concurrent/ThreadRobustListTestCase.java
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+// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.concurrent;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.fail;
+
+import java.util.Iterator;
+
+import org.junit.Test;
+
+/**
+ * Check we keep the consistent view when reading and writing in parallell.
+ *
+ * @author <a href="mailto:steinar@yahoo-inc.com">Steinar Knutsen</a>
+ */
+public class ThreadRobustListTestCase {
+
+    private static class Writer implements Runnable {
+        private final ThreadRobustList<String> l;
+        private final Receiver<Boolean> sharedLock;
+
+        public Writer(final ThreadRobustList<String> l,
+                final Receiver<Boolean> sharedLock) {
+            this.sharedLock = sharedLock;
+            this.l = l;
+        }
+
+        @Override
+        public void run() {
+            for (int i = 0; i < 5; ++i) {
+                l.add(String.valueOf(i));
+            }
+            sharedLock.put(Boolean.TRUE);
+            for (int i = 5; i < 100 * 1000; ++i) {
+                l.add(String.valueOf(i));
+            }
+        }
+
+    }
+
+    private static class Reader implements Runnable {
+        private final ThreadRobustList<String> l;
+        private final Receiver<Boolean> sharedLock;
+
+        public Reader(final ThreadRobustList<String> l,
+                final Receiver<Boolean> sharedLock) {
+            this.sharedLock = sharedLock;
+            this.l = l;
+        }
+
+        @Override
+        public void run() {
+            int n;
+            int previous;
+
+            try {
+                sharedLock.get(5 * 60 * 1000);
+            } catch (final InterruptedException e) {
+                fail("Test interrupted.");
+            }
+            n = countElements();
+            assertFalse(n < 5);
+            previous = n;
+            for (int i = 0; i < 1000; ++i) {
+                int reverse = reverseCountElements();
+                n = countElements();
+                assertFalse(n < reverse);
+                assertFalse(n < previous);
+                previous = n;
+            }
+        }
+
+        private int reverseCountElements() {
+            int n = 0;
+            for (final Iterator<String> j = l.reverseIterator(); j.hasNext(); j.next()) {
+                ++n;
+            }
+            return n;
+        }
+
+        private int countElements() {
+            int n = 0;
+            for (final Iterator<String> j = l.iterator(); j.hasNext(); j.next()) {
+                ++n;
+            }
+            return n;
+        }
+    }
+
+    @Test
+    public final void test() throws InterruptedException {
+        final ThreadRobustList<String> container = new ThreadRobustList<>();
+        final Receiver<Boolean> lock = new Receiver<>();
+        final Reader r = new Reader(container, lock);
+        final Writer w = new Writer(container, lock);
+        final Thread wt = new Thread(w);
+        wt.start();
+        r.run();
+        wt.join();
+    }
+
+}