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/*
 * 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.hadoop.hbase.io.hfile;

import java.io.DataOutputStream;
import java.io.IOException;

import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.hbase.Cell;
import org.apache.hadoop.hbase.io.encoding.DataBlockEncoding;
import org.apache.hadoop.hbase.io.encoding.HFileBlockDecodingContext;
import org.apache.hadoop.hbase.io.encoding.HFileBlockEncodingContext;
import org.apache.hadoop.hbase.util.Bytes;

/**
 * Controls what kind of data block encoding is used. If data block encoding is
 * not set or the given block is not a data block (encoded or not), methods
 * should just return the unmodified block.
 */
@InterfaceAudience.Private
public interface HFileDataBlockEncoder {
  /** Type of encoding used for data blocks in HFile. Stored in file info. */
  byte[] DATA_BLOCK_ENCODING = Bytes.toBytes("DATA_BLOCK_ENCODING");

  /**
   * Starts encoding for a block of KeyValues. Call
   * {@link #endBlockEncoding(HFileBlockEncodingContext, DataOutputStream, byte[], BlockType)}
   * to finish encoding of a block.
   * @param encodingCtx
   * @param out
   * @throws IOException
   */
  void startBlockEncoding(HFileBlockEncodingContext encodingCtx, DataOutputStream out)
      throws IOException;

  /**
   * Encodes a KeyValue.
   * @param cell
   * @param encodingCtx
   * @param out
   * @return unencoded kv size
   * @throws IOException
   */
  int encode(Cell cell, HFileBlockEncodingContext encodingCtx, DataOutputStream out)
      throws IOException;

  /**
   * Ends encoding for a block of KeyValues. Gives a chance for the encoder to do the finishing
   * stuff for the encoded block. It must be called at the end of block encoding.
   * @param encodingCtx
   * @param out
   * @param uncompressedBytesWithHeader
   * @param blockType
   * @throws IOException
   */
  void endBlockEncoding(HFileBlockEncodingContext encodingCtx, DataOutputStream out,
      byte[] uncompressedBytesWithHeader, BlockType blockType) throws IOException;

  /**
   * Decides whether we should use a scanner over encoded blocks.
   * @return Whether to use encoded scanner.
   */
  boolean useEncodedScanner();

  /**
   * Save metadata in HFile which will be written to disk
   * @param writer writer for a given HFile
   * @exception IOException on disk problems
   */
  void saveMetadata(HFile.Writer writer)
      throws IOException;

  /** @return the data block encoding */
  DataBlockEncoding getDataBlockEncoding();

  /**
   * @return the effective in-cache data block encoding, taking into account
   *         whether we are doing a compaction.
   */
  public DataBlockEncoding getEffectiveEncodingInCache(boolean isCompaction);

  /**
   * Create an encoder specific encoding context object for writing. And the
   * encoding context should also perform compression if compressionAlgorithm is
   * valid.
   *
   * @param headerBytes header bytes
   * @param fileContext HFile meta data
   * @return a new {@link HFileBlockEncodingContext} object
   */
  HFileBlockEncodingContext newDataBlockEncodingContext(byte[] headerBytes,
      HFileContext fileContext);

  /**
   * create a encoder specific decoding context for reading. And the
   * decoding context should also do decompression if compressionAlgorithm
   * is valid.
   *
   * @param fileContext - HFile meta data
   * @return a new {@link HFileBlockDecodingContext} object
   */
  HFileBlockDecodingContext newDataBlockDecodingContext(HFileContext fileContext);
}