Factor out FileWriter interface

[controller.git] / atomix-storage / src / main / java / io / atomix / storage / journal / MappedFileWriter.java

diff --git a/atomix-storage/src/main/java/io/atomix/storage/journal/MappedFileWriter.java b/atomix-storage/src/main/java/io/atomix/storage/journal/MappedFileWriter.java
new file mode 100644 (file)
index 0000000..d1bbd7d
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+++ b/atomix-storage/src/main/java/io/atomix/storage/journal/MappedFileWriter.java
@@ -0,0 +1,100 @@
+/*
+ * Copyright (c) 2024 PANTHEON.tech, s.r.o. and others.  All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.atomix.storage.journal;
+
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.MappedByteBuffer;
+import java.nio.channels.FileChannel;
+import java.nio.file.Path;
+import org.eclipse.jdt.annotation.NonNull;
+
+/**
+ * A {@link StorageLevel#MAPPED} {@link FileWriter}.
+ */
+final class MappedFileWriter extends FileWriter {
+    private final @NonNull MappedByteBuffer mappedBuffer;
+    private final MappedFileReader reader;
+    private final ByteBuffer buffer;
+
+    MappedFileWriter(final Path path, final FileChannel channel, final int maxSegmentSize, final int maxEntrySize) {
+        super(path, channel, maxSegmentSize, maxEntrySize);
+
+        mappedBuffer = mapBuffer(channel, maxSegmentSize);
+        buffer = mappedBuffer.slice();
+        reader = new MappedFileReader(path, mappedBuffer);
+    }
+
+    private static @NonNull MappedByteBuffer mapBuffer(final FileChannel channel, final int maxSegmentSize) {
+        try {
+            return channel.map(FileChannel.MapMode.READ_WRITE, 0, maxSegmentSize);
+        } catch (IOException e) {
+            throw new StorageException(e);
+        }
+    }
+
+    @Override
+    MappedFileReader reader() {
+        return reader;
+    }
+
+    @Override
+    MappedByteBuffer buffer() {
+        return mappedBuffer;
+    }
+
+    @Override
+    MappedFileWriter toMapped() {
+        return null;
+    }
+
+    @Override
+    DiskFileWriter toDisk() {
+        close();
+        return new DiskFileWriter(path, channel, maxSegmentSize, maxEntrySize);
+    }
+
+    @Override
+    void writeEmptyHeader(final int position) {
+        // Note: we issue a single putLong() instead of two putInt()s.
+        buffer.putLong(position, 0L);
+    }
+
+    @Override
+    ByteBuffer startWrite(final int position, final int size) {
+        return buffer.slice(position, size);
+    }
+
+    @Override
+    void commitWrite(final int position, final ByteBuffer entry) {
+        // No-op, buffer is write-through
+    }
+
+    @Override
+    void flush() {
+        mappedBuffer.force();
+    }
+
+    @Override
+    void close() {
+        flush();
+        try {
+            BufferCleaner.freeBuffer(mappedBuffer);
+        } catch (IOException e) {
+            throw new StorageException(e);
+        }
+    }
+}