From 0e616d9dcc705323684a20e76175ef750b28db48 Mon Sep 17 00:00:00 2001
From: James Watson <james@weareadaptive.com>
Date: Mon, 28 Oct 2019 01:07:28 +0000
Subject: [PATCH 1/2] [Java] Add test for ExpandableRingBuffer to assert
 capacity.

---
 .../org/agrona/ExpandableRingBufferTest.java  | 21 +++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/agrona/src/test/java/org/agrona/ExpandableRingBufferTest.java b/agrona/src/test/java/org/agrona/ExpandableRingBufferTest.java
index 4f6c55330..bdce171e7 100644
--- a/agrona/src/test/java/org/agrona/ExpandableRingBufferTest.java
+++ b/agrona/src/test/java/org/agrona/ExpandableRingBufferTest.java
@@ -17,6 +17,7 @@
 
 import org.agrona.concurrent.UnsafeBuffer;
 
+import org.junit.Ignore;
 import org.junit.Test;
 import org.mockito.InOrder;
 import org.mockito.Mockito;
@@ -181,6 +182,26 @@ public void shouldAppendThenIterateMessagesInOrder()
         inOrder.verify(mockConsumer).onMessage(any(MutableDirectBuffer.class), anyInt(), eq(MSG_LENGTH_TWO), anyInt());
     }
 
+    @Test
+    @Ignore
+    public void shouldAppendMessagesWithinCapacityWithoutExpanding()
+    {
+        final int initialCapacity = 1024;
+        final int maxCapacity = 2048;
+
+        final ExpandableRingBuffer ringBuffer = new ExpandableRingBuffer(initialCapacity, maxCapacity, false);
+
+        final ExpandableRingBuffer.MessageConsumer mockConsumer = mock(ExpandableRingBuffer.MessageConsumer.class);
+        when(mockConsumer.onMessage(any(), anyInt(), anyInt(), anyInt())).thenReturn(Boolean.TRUE);
+
+        assertThat(ringBuffer.capacity(), is(initialCapacity));
+
+        final int messageLength = 32;
+        ringBuffer.append(TEST_MSG, 0, messageLength);
+
+        assertThat(ringBuffer.capacity(), is(initialCapacity));
+    }
+
     @Test
     public void shouldAppendMessagesWithPaddingWithoutExpanding()
     {

From 8951d951d525da9d122a45e2f8e56c1fb18ddb11 Mon Sep 17 00:00:00 2001
From: James Watson <james@weareadaptive.com>
Date: Mon, 28 Oct 2019 01:10:56 +0000
Subject: [PATCH 2/2] [Java] Only increase capacity when necessary.

---
 .../java/org/agrona/ExpandableRingBuffer.java | 20 +++++++++++--------
 .../org/agrona/ExpandableRingBufferTest.java  |  2 --
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/agrona/src/main/java/org/agrona/ExpandableRingBuffer.java b/agrona/src/main/java/org/agrona/ExpandableRingBuffer.java
index 957593c38..1af2d854a 100644
--- a/agrona/src/main/java/org/agrona/ExpandableRingBuffer.java
+++ b/agrona/src/main/java/org/agrona/ExpandableRingBuffer.java
@@ -386,15 +386,19 @@ public boolean append(final DirectBuffer srcBuffer, final int srcOffset, final i
         else if (tailOffset >= headOffset)
         {
             final int toEndRemaining = capacity - tailOffset;
-            if (alignedLength > toEndRemaining && alignedLength <= (totalRemaining - toEndRemaining))
-            {
-                buffer.putInt(tailOffset + MESSAGE_LENGTH_OFFSET, toEndRemaining);
-                buffer.putInt(tailOffset + MESSAGE_TYPE_OFFSET, MESSAGE_TYPE_PADDING);
-                tail += toEndRemaining;
-            }
-            else
+
+            if (alignedLength > toEndRemaining)
             {
-                resize(alignedLength);
+                if (alignedLength <= (totalRemaining - toEndRemaining))
+                {
+                    buffer.putInt(tailOffset + MESSAGE_LENGTH_OFFSET, toEndRemaining);
+                    buffer.putInt(tailOffset + MESSAGE_TYPE_OFFSET, MESSAGE_TYPE_PADDING);
+                    tail += toEndRemaining;
+                }
+                else
+                {
+                    resize(alignedLength);
+                }
             }
         }
 
diff --git a/agrona/src/test/java/org/agrona/ExpandableRingBufferTest.java b/agrona/src/test/java/org/agrona/ExpandableRingBufferTest.java
index bdce171e7..d8fe77057 100644
--- a/agrona/src/test/java/org/agrona/ExpandableRingBufferTest.java
+++ b/agrona/src/test/java/org/agrona/ExpandableRingBufferTest.java
@@ -17,7 +17,6 @@
 
 import org.agrona.concurrent.UnsafeBuffer;
 
-import org.junit.Ignore;
 import org.junit.Test;
 import org.mockito.InOrder;
 import org.mockito.Mockito;
@@ -183,7 +182,6 @@ public void shouldAppendThenIterateMessagesInOrder()
     }
 
     @Test
-    @Ignore
     public void shouldAppendMessagesWithinCapacityWithoutExpanding()
     {
         final int initialCapacity = 1024;