/*
    * 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.IOException;
  import java.io.InputStream;
  import java.nio.ByteBuffer;
  
  import org.apache.commons.io.IOUtils;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.io.ByteBufferInputStream;
  import org.apache.hadoop.hbase.io.TagCompressionContext;
  import org.apache.hadoop.hbase.io.compress.Compression;
  import org.apache.hadoop.hbase.io.crypto.Cipher;
  import org.apache.hadoop.hbase.io.crypto.Decryptor;
  import org.apache.hadoop.hbase.io.crypto.Encryption;
  import org.apache.hadoop.hbase.io.hfile.HFileContext;
  import org.apache.hadoop.hbase.util.Bytes;
  
  /**
   * A default implementation of {@link HFileBlockDecodingContext}. It assumes the
   * block data section is compressed as a whole.
   *
   * @see HFileBlockDefaultEncodingContext for the default compression context
   *
   */
  @InterfaceAudience.Private
  public class HFileBlockDefaultDecodingContext implements
      HFileBlockDecodingContext {
    private final HFileContext fileContext;
    private TagCompressionContext tagCompressionContext;
    
    public HFileBlockDefaultDecodingContext(HFileContext fileContext) {
      this.fileContext = fileContext;
    }
  
    @Override
    public void prepareDecoding(int onDiskSizeWithoutHeader, int uncompressedSizeWithoutHeader,
        ByteBuffer blockBufferWithoutHeader, ByteBuffer onDiskBlock) throws IOException {
      InputStream in = new DataInputStream(new ByteBufferInputStream(onDiskBlock));
  
      Encryption.Context cryptoContext = fileContext.getEncryptionContext();
      if (cryptoContext != Encryption.Context.NONE) {
  
        Cipher cipher = cryptoContext.getCipher();
        Decryptor decryptor = cipher.getDecryptor();
        decryptor.setKey(cryptoContext.getKey());
  
        // Encrypted block format:
        // +--------------------------+
        // | byte iv length           |
        // +--------------------------+
        // | iv data ...              |
        // +--------------------------+
        // | encrypted block data ... |
        // +--------------------------+
  
        int ivLength = in.read();
        if (ivLength > 0) {
          byte[] iv = new byte[ivLength];
          IOUtils.readFully(in, iv);
          decryptor.setIv(iv);
          // All encrypted blocks will have a nonzero IV length. If we see an IV
          // length of zero, this means the encoding context had 0 bytes of
          // plaintext to encode.
          decryptor.reset();
          in = decryptor.createDecryptionStream(in);
        }
        onDiskSizeWithoutHeader -= Bytes.SIZEOF_BYTE + ivLength;
      }
  
      Compression.Algorithm compression = fileContext.getCompression();
      assert blockBufferWithoutHeader.hasArray();
      if (compression != Compression.Algorithm.NONE) {
        Compression.decompress(blockBufferWithoutHeader.array(),
          blockBufferWithoutHeader.arrayOffset(), in, onDiskSizeWithoutHeader,
          uncompressedSizeWithoutHeader, compression);
      } else {
        IOUtils.readFully(in, blockBufferWithoutHeader.array(),
          blockBufferWithoutHeader.arrayOffset(), onDiskSizeWithoutHeader);
      }
    }
  
    @Override
   public HFileContext getHFileContext() {
     return this.fileContext;
   }
 
   public TagCompressionContext getTagCompressionContext() {
     return tagCompressionContext;
   }
 
   public void setTagCompressionContext(TagCompressionContext tagCompressionContext) {
     this.tagCompressionContext = tagCompressionContext;
   }
 }