package org.apache.archiva.checksum;
   
   /*
    * 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.
   */
  
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.nio.MappedByteBuffer;
  import java.nio.channels.FileChannel;
  import java.nio.file.Path;
  import java.nio.file.StandardOpenOption;
  import java.util.List;
  import java.util.stream.Collectors;
  
  /**
   * Utility class that handles multiple checksums for a single file.
   */
  public class ChecksumUtil {
  
  
      static final int BUFFER_SIZE = 32768;
  
      public static void update(List<Checksum> checksumList, Path file ) throws IOException {
          long fileSize;
          try (FileChannel channel = FileChannel.open(file, StandardOpenOption.READ )) {
              fileSize = channel.size();
              long pos = 0;
              while (pos < fileSize) {
                  long bufferSize = Math.min(BUFFER_SIZE, fileSize - pos);
                  MappedByteBuffer buffer = channel.map(FileChannel.MapMode.READ_ONLY, pos, bufferSize);
                  for (Checksum checksum : checksumList) {
                      checksum.update(buffer);
                      buffer.rewind();
                  }
                  fileSize = channel.size();
                  pos += BUFFER_SIZE;
              }
              for (Checksum checksum : checksumList) {
                  checksum.finish();
              }
          }
      }
  
      public static void update(Checksum checksum, Path file)
          throws IOException
      {
          long fileSize;
          try (FileChannel channel = FileChannel.open(file, StandardOpenOption.READ )) {
              fileSize = channel.size();
              long pos = 0;
              while (pos<fileSize)
              {
                  long bufferSize = Math.min(BUFFER_SIZE, fileSize-pos);
                  MappedByteBuffer buffer = channel.map( FileChannel.MapMode.READ_ONLY, pos, bufferSize);
                  checksum.update( buffer );
                  buffer.rewind();
                  fileSize = channel.size();
                  pos += BUFFER_SIZE;
              }
              checksum.finish();
          }
      }
  
      public static List<Checksum> initializeChecksums(Path file, List<ChecksumAlgorithm> checksumAlgorithms) throws IOException {
          final List<Checksum> checksums = newChecksums(checksumAlgorithms);
          update(checksums, file);
          return checksums;
      }
  
      /**
       * Returns the list of configured checksum types.
       *
       * @param checksumTypes The list of checksum strings
       * @return The list of checksum objects
       */
      public static List<ChecksumAlgorithm> getAlgorithms(List<String> checksumTypes) {
          return checksumTypes.stream().map(ca ->
                  ChecksumAlgorithm.valueOf(ca.toUpperCase())).collect(Collectors.toList());
      }
  
      public static List<Checksum> newChecksums(List<ChecksumAlgorithm> checksumAlgorithms) {
          return checksumAlgorithms.stream().map( a -> new Checksum(a)).collect(Collectors.toList());
      }
 
 }