Fixed acquireNextByteStore0 when shifting backwards, closes #452

OpenHFT · Oct 7, 2022 · 49a8b78 · 49a8b78
1 parent 442e7c8
commit 49a8b78
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Showing 2 changed files with 28 additions and 1 deletion.
diff --git a/src/main/java/net/openhft/chronicle/bytes/internal/ChunkedMappedBytes.java b/src/main/java/net/openhft/chronicle/bytes/internal/ChunkedMappedBytes.java
@@ -269,7 +269,11 @@ protected void writeCheckOffset(final long offset, final long adding)
             throw writeBufferOverflowException0(offset);
         BytesStore bytesStore = this.bytesStore;
         if (adding > 0 && !bytesStore.inside(offset, checkSize0(adding - 1))) {
-            acquireNextByteStore0(offset + adding - 1, false);
+            if (bytesStore.start() > offset)
+                acquireNextByteStore0(offset, false);
+            else
+                acquireNextByteStore0(offset + adding - 1, false);
+
             if (!this.bytesStore.inside(offset, checkSize0(adding - 1)))
                 throw new DecoratedBufferUnderflowException(String.format("Acquired the next BytesStore, but still not room to add %d when realCapacity %d", adding, this.bytesStore.realCapacity()));
         }

diff --git a/src/test/java/net/openhft/chronicle/bytes/MappedBytesTest.java b/src/test/java/net/openhft/chronicle/bytes/MappedBytesTest.java
@@ -19,6 +19,7 @@
 import java.util.Random;
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.ThreadLocalRandom;
 import java.util.stream.IntStream;
 
 import static org.junit.Assert.*;
@@ -75,6 +76,28 @@ public void testMappedFileSafeLimitTooSmall()
         }
     }
 
+    @Test
+    public void testAcquireNextByteStoreShiftingBackwards() throws IOException {
+        final long chunkSize = OS.mapAlign(40_000);
+
+        File tempFile1 = File.createTempFile("mapped", "bytes");
+        try (MappedBytes bytesW = MappedBytes.mappedBytes(tempFile1, chunkSize, chunkSize)) {
+
+            for (int i = 0; i < chunkSize / 4; i++)
+                bytesW.writeLong(ThreadLocalRandom.current().nextLong());
+
+            Assert.assertEquals(chunkSize * 2, bytesW.writePosition());
+
+            bytesW.writeInt(7);
+            Assert.assertEquals(chunkSize * 2 + 4, bytesW.writePosition());
+
+            bytesW.writeInt(chunkSize * 2 - 2, 9);
+
+            bytesW.readPosition(chunkSize * 2 - 2);
+            Assert.assertEquals(9, bytesW.readInt());
+        }
+    }
+
     @Test
     public void testMappedFileSafeLimitTooSmall2()
             throws IOException {