Updates to ReadAheadChannel after review.

community/kernel/src/main/java/org/neo4j/kernel/impl/transaction/log/ReadAheadChannel.java

@@ -54,9 +54,16 @@ public ReadAheadChannel( T channel, int readAheadSize )
         this.readAheadSize = readAheadSize;
     }
 
+    /**
+     * This is the position within the buffered stream (and not the
+     * underlying channel, which will generally be further ahead).
+     *
+     * @return The position within the buffered stream.
+     * @throws IOException
+     */
     public long position() throws IOException
     {
-        return offset();
+        return channel.position() - aheadBuffer.remaining();
     }
 
     @Override
@@ -173,11 +180,6 @@ protected T next( T channel ) throws IOException
         return channel;
     }
 
-    protected long offset() throws IOException
-    {
-        return channel.position() - aheadBuffer.remaining();
-    }
-
     /*
      * Moves bytes between aheadBuffer.position() and aheadBuffer.capacity() to the beginning of aheadBuffer. At the
      * end of this call the aheadBuffer is positioned in end of that moved content.

community/kernel/src/main/java/org/neo4j/kernel/impl/transaction/log/ReadAheadLogChannel.java

@@ -56,7 +56,7 @@ public byte getLogFormatVersion()
     @Override
     public LogPositionMarker getCurrentPosition( LogPositionMarker positionMarker ) throws IOException
     {
-        positionMarker.mark( channel.getVersion(), offset() );
+        positionMarker.mark( channel.getVersion(), position() );
         return positionMarker;
     }
 

community/kernel/src/test/java/org/neo4j/kernel/impl/transaction/log/ReadAheadChannelTest.java

@@ -170,4 +170,52 @@ protected StoreChannel next( StoreChannel channel ) throws IOException
             // outstanding
         }
     }
+
+    @Test
+    public void shouldReturnPositionWithinBufferedStream() throws Exception
+    {
+        // given
+        EphemeralFileSystemAbstraction fsa = new EphemeralFileSystemAbstraction();
+        File file = new File( "foo.txt" );
+
+        int readAheadSize = 512;
+        int fileSize = readAheadSize * 8;
+
+        createFile( fsa, file, fileSize );
+        ReadAheadChannel<StoreChannel> bufferedReader = new ReadAheadChannel<>( fsa.open( file, "r" ), readAheadSize );
+
+        // when
+        for ( int i = 0; i < fileSize / Long.BYTES; i++ )
+        {
+            assertEquals( Long.BYTES * i, bufferedReader.position() );
+            bufferedReader.getLong();
+        }
+
+        assertEquals( fileSize, bufferedReader.position() );
+
+        try
+        {
+            bufferedReader.getLong();
+            fail();
+        }
+        catch ( ReadPastEndException e )
+        {
+            // expected
+        }
+
+        assertEquals( fileSize, bufferedReader.position() );
+    }
+
+    private void createFile( EphemeralFileSystemAbstraction fsa, File name, int bufferSize ) throws IOException
+    {
+        StoreChannel storeChannel = fsa.open( name, "w" );
+        ByteBuffer buffer = ByteBuffer.allocate( bufferSize );
+        for ( int i = 0; i < bufferSize; i++ )
+        {
+            buffer.put( (byte) i );
+        }
+        buffer.flip();
+        storeChannel.writeAll( buffer );
+        storeChannel.close();
+    }
 }