/*
    * 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.encoding;
  
  import java.io.DataInputStream;
  import java.io.DataOutputStream;
  import java.io.IOException;
  import java.nio.ByteBuffer;
  
  import org.apache.hadoop.hbase.Cell;
  import org.apache.hadoop.hbase.KeyValue.KVComparator;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.util.ByteBufferUtils;
  import org.apache.hadoop.hbase.util.Bytes;
  
  /**
   * Just copy data, do not do any kind of compression. Use for comparison and
   * benchmarking.
   */
  @InterfaceAudience.Private
  public class CopyKeyDataBlockEncoder extends BufferedDataBlockEncoder {
  
    private static class CopyKeyEncodingState extends EncodingState {
      NoneEncoder encoder = null;
    }
  
    @Override
    public void startBlockEncoding(HFileBlockEncodingContext blkEncodingCtx,
        DataOutputStream out) throws IOException {
      if (blkEncodingCtx.getClass() != HFileBlockDefaultEncodingContext.class) {
        throw new IOException(this.getClass().getName() + " only accepts "
            + HFileBlockDefaultEncodingContext.class.getName() + " as the "
            + "encoding context.");
      }
  
      HFileBlockDefaultEncodingContext encodingCtx = (HFileBlockDefaultEncodingContext) blkEncodingCtx;
      encodingCtx.prepareEncoding(out);
  
      NoneEncoder encoder = new NoneEncoder(out, encodingCtx);
      CopyKeyEncodingState state = new CopyKeyEncodingState();
      state.encoder = encoder;
      blkEncodingCtx.setEncodingState(state);
    }
  
    @Override
    public int internalEncode(Cell cell,
        HFileBlockDefaultEncodingContext encodingContext, DataOutputStream out)
        throws IOException {
      CopyKeyEncodingState state = (CopyKeyEncodingState) encodingContext
          .getEncodingState();
      NoneEncoder encoder = state.encoder;
      return encoder.write(cell);
    }
  
    @Override
    public ByteBuffer getFirstKeyInBlock(ByteBuffer block) {
      int keyLength = block.getInt(Bytes.SIZEOF_INT);
      ByteBuffer dup = block.duplicate();
      int pos = 3 * Bytes.SIZEOF_INT;
      dup.position(pos);
      dup.limit(pos + keyLength);
      return dup.slice();
    }
  
    @Override
    public String toString() {
      return CopyKeyDataBlockEncoder.class.getSimpleName();
    }
  
    @Override
    public EncodedSeeker createSeeker(KVComparator comparator,
        final HFileBlockDecodingContext decodingCtx) {
      return new BufferedEncodedSeeker<SeekerState>(comparator, decodingCtx) {
        @Override
        protected void decodeNext() {
          current.keyLength = currentBuffer.getInt();
          current.valueLength = currentBuffer.getInt();
          current.ensureSpaceForKey();
          currentBuffer.get(current.keyBuffer, 0, current.keyLength);
          current.valueOffset = currentBuffer.position();
          ByteBufferUtils.skip(currentBuffer, current.valueLength);
          if (includesTags()) {
            // Read short as unsigned, high byte first
            current.tagsLength = ((currentBuffer.get() & 0xff) << 8) ^ (currentBuffer.get() & 0xff);
            ByteBufferUtils.skip(currentBuffer, current.tagsLength);
         }
         if (includesMvcc()) {
           current.memstoreTS = ByteBufferUtils.readVLong(currentBuffer);
         } else {
           current.memstoreTS = 0;
         }
         current.nextKvOffset = currentBuffer.position();
       }
 
       @Override
       protected void decodeFirst() {
         ByteBufferUtils.skip(currentBuffer, Bytes.SIZEOF_INT);
         current.lastCommonPrefix = 0;
         decodeNext();
       }
     };
   }
 
   @Override
   protected ByteBuffer internalDecodeKeyValues(DataInputStream source, int allocateHeaderLength,
       int skipLastBytes, HFileBlockDefaultDecodingContext decodingCtx) throws IOException {
     int decompressedSize = source.readInt();
     ByteBuffer buffer = ByteBuffer.allocate(decompressedSize +
         allocateHeaderLength);
     buffer.position(allocateHeaderLength);
     ByteBufferUtils.copyFromStreamToBuffer(buffer, source, decompressedSize);
 
     return buffer;
   }
 }