content: /*
   * Copyright (C) 2010-2101 Alibaba Group Holding Limited.
   *
   * 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 com.alibaba.otter.node.etl.common.io.compress.impl;
  
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.IOException;
  import java.util.Iterator;
  import java.util.List;
  
  import org.apache.commons.io.IOUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Abstract super object for Compressor and Archiver classes.
   */
  public abstract class PackableObject {
  
      /* Type for archive choosing: String */
      protected static final int CHOOSE_EXTENSION = 1;
  
      /* Type for archive choosing: Long */
      protected static final int CHOOSE_NAME      = 2;
  
      protected final Logger     logger           = LoggerFactory.getLogger(getClass());
  
      /**
       * Header byte array for this archive.
       */
      public abstract byte[] getHeader();
  
      /**
       * Returns the default FileExtension for this archive, for example "zip",
       * "tar"...
       */
      public abstract String getDefaultFileExtension();
  
      /**
       * Returns the ArchiveName for this archive.
       */
      public abstract String getName();
  
      /**
       * String Chooser.
       */
      protected boolean isPackableWith(Object value, int choose) {
          if (value == null) {
              return false;
          }
  
          if (choose == CHOOSE_EXTENSION) {
              if (value.equals(getDefaultFileExtension())) {
                  return true;
              }
          } else if (choose == CHOOSE_NAME) {
              if (value.equals(getName())) {
                  return true;
              }
          }
  
          return false;
      }
  
      /**
       * Compares a file to a list of packables and identifies an object by
       * header. If no matching header is found, it identifies the file by file
       * extension. If identification was not successfull, null is returned
       * 
       * @param file the file to identify
       * @param packables a list of packables
       * @return a matching packable object, or null
       * @throws IOException
       */
      public static PackableObject identifyByHeader(File file, List packables) throws IOException {
          FileInputStream fis = null;
          try {
              /* Archive result */
              // PackableObject packable = null;
              // identify archive by header
              fis = new FileInputStream(file);
              byte[] headerBytes = new byte[20];
              fis.read(headerBytes, 0, 20);
  
              Iterator iter = packables.iterator();
              while (iter.hasNext()) {
                  PackableObject p = (PackableObject) iter.next();
                  byte[] fieldHeader = p.getHeader();
  
                  if (fieldHeader != null) {
                      if (compareByteArrays(headerBytes, fieldHeader)) {
                          return p;
                      }
                  }
              }
  
              // if we couldn't find an archiver by header bytes, we'll give it a
              // try
              // with the default name extension. This is useful, cause some
              // archives
              // like tar have no header.
              String name = file.getName();
              String extension = null;
              String[] s = name.split("\\.");
  
              if (s.length > 1) {
                  extension = s[s.length - 1];
              }
  
              Iterator it = packables.iterator();
  
              while (it.hasNext()) {
                  PackableObject p = (PackableObject) it.next();
                  if (p.isPackableWith(extension, PackableObject.CHOOSE_EXTENSION)) {
                      return p;
                  }
              }
              // No implementation found
              return null;
          } finally {
              IOUtils.closeQuietly(fis);
          }
      }
  
      private static boolean compareByteArrays(byte[] source, byte[] match) {
          int i = 0;
          while ((source.length < i) || (i < match.length)) {
              if (source[i] != match[i]) {
                  return false;
              }
              i++;
          }
          return true;
      }
  }
  