import quincy 17.2.0

[ceph.git] / ceph / src / arrow / java / vector / src / main / java / org / apache / arrow / vector / compression / AbstractCompressionCodec.java

diff --git a/ceph/src/arrow/java/vector/src/main/java/org/apache/arrow/vector/compression/AbstractCompressionCodec.java b/ceph/src/arrow/java/vector/src/main/java/org/apache/arrow/vector/compression/AbstractCompressionCodec.java
new file mode 100644 (file)
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+++ b/ceph/src/arrow/java/vector/src/main/java/org/apache/arrow/vector/compression/AbstractCompressionCodec.java
@@ -0,0 +1,116 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.arrow.vector.compression;
+
+import org.apache.arrow.memory.ArrowBuf;
+import org.apache.arrow.memory.BufferAllocator;
+import org.apache.arrow.memory.util.MemoryUtil;
+import org.apache.arrow.util.Preconditions;
+
+/**
+ * The base class for concrete compression codecs, providing
+ * common logic for all compression codecs.
+ */
+public abstract class AbstractCompressionCodec implements CompressionCodec {
+
+  @Override
+  public ArrowBuf compress(BufferAllocator allocator, ArrowBuf uncompressedBuffer) {
+    if (uncompressedBuffer.writerIndex() == 0L) {
+      // shortcut for empty buffer
+      ArrowBuf compressedBuffer = allocator.buffer(CompressionUtil.SIZE_OF_UNCOMPRESSED_LENGTH);
+      compressedBuffer.setLong(0, 0);
+      compressedBuffer.writerIndex(CompressionUtil.SIZE_OF_UNCOMPRESSED_LENGTH);
+      uncompressedBuffer.close();
+      return compressedBuffer;
+    }
+
+    ArrowBuf compressedBuffer = doCompress(allocator, uncompressedBuffer);
+    long compressedLength = compressedBuffer.writerIndex() - CompressionUtil.SIZE_OF_UNCOMPRESSED_LENGTH;
+    long uncompressedLength = uncompressedBuffer.writerIndex();
+
+    if (compressedLength > uncompressedLength) {
+      // compressed buffer is larger, send the raw buffer
+      compressedBuffer.close();
+      compressedBuffer = CompressionUtil.packageRawBuffer(allocator, uncompressedBuffer);
+    } else {
+      writeUncompressedLength(compressedBuffer, uncompressedLength);
+    }
+
+    uncompressedBuffer.close();
+    return compressedBuffer;
+  }
+
+  @Override
+  public ArrowBuf decompress(BufferAllocator allocator, ArrowBuf compressedBuffer) {
+    Preconditions.checkArgument(compressedBuffer.writerIndex() >= CompressionUtil.SIZE_OF_UNCOMPRESSED_LENGTH,
+        "Not enough data to decompress.");
+
+    long decompressedLength = readUncompressedLength(compressedBuffer);
+
+    if (decompressedLength == 0L) {
+      // shortcut for empty buffer
+      compressedBuffer.close();
+      return allocator.getEmpty();
+    }
+
+    if (decompressedLength == CompressionUtil.NO_COMPRESSION_LENGTH) {
+      // no compression
+      return CompressionUtil.extractUncompressedBuffer(compressedBuffer);
+    }
+
+    ArrowBuf decompressedBuffer = doDecompress(allocator, compressedBuffer);
+    compressedBuffer.close();
+    return decompressedBuffer;
+  }
+
+  protected void writeUncompressedLength(ArrowBuf compressedBuffer, long uncompressedLength) {
+    if (!MemoryUtil.LITTLE_ENDIAN) {
+      uncompressedLength = Long.reverseBytes(uncompressedLength);
+    }
+    // first 8 bytes reserved for uncompressed length, according to the specification
+    compressedBuffer.setLong(0, uncompressedLength);
+  }
+
+  protected long readUncompressedLength(ArrowBuf compressedBuffer) {
+    long decompressedLength = compressedBuffer.getLong(0);
+    if (!MemoryUtil.LITTLE_ENDIAN) {
+      decompressedLength = Long.reverseBytes(decompressedLength);
+    }
+    return decompressedLength;
+  }
+
+  /**
+   * The method that actually performs the data compression.
+   * The layout of the returned compressed buffer is the compressed data,
+   * plus 8 bytes reserved at the beginning of the buffer for the uncompressed data size.
+   * <p>
+   *   Please note that this method is not responsible for releasing the uncompressed buffer.
+   * </p>
+   */
+  protected abstract ArrowBuf doCompress(BufferAllocator allocator, ArrowBuf uncompressedBuffer);
+
+  /**
+   * The method that actually performs the data decompression.
+   * The layout of the compressed buffer is the compressed data,
+   * plus 8 bytes at the beginning of the buffer storing the uncompressed data size.
+   * <p>
+   *   Please note that this method is not responsible for releasing the compressed buffer.
+   * </p>
+   */
+  protected abstract ArrowBuf doDecompress(BufferAllocator allocator, ArrowBuf compressedBuffer);
+}