content: /*
   * Copyright 2002-2019 Drew Noakes and contributors
   *
   *    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
   *
   *        https://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.
   *
   * More information about this project is available at:
   *
   *    https://drewnoakes.com/code/exif/
   *    https://github.com/drewnoakes/metadata-extractor
   */
  
  package com.drew.lang;
  
  import com.drew.lang.annotations.NotNull;
  
  import java.io.IOException;
  import java.io.RandomAccessFile;
  
  /**
   * Provides methods to read specific values from a {@link RandomAccessFile}, with a consistent, checked exception structure for
   * issues.
   *
   * @author Drew Noakes https://drewnoakes.com
   * */
  public class RandomAccessFileReader extends RandomAccessReader
  {
      @NotNull
      private final RandomAccessFile _file;
      private final long _length;
      private int _currentIndex;
  
      private final int _baseOffset;
  
      @SuppressWarnings({ "ConstantConditions" })
      @com.drew.lang.annotations.SuppressWarnings(value = "EI_EXPOSE_REP2", justification = "Design intent")
      public RandomAccessFileReader(@NotNull RandomAccessFile file) throws IOException
      {
          this(file, 0);
      }
  
      @SuppressWarnings({ "ConstantConditions" })
      @com.drew.lang.annotations.SuppressWarnings(value = "EI_EXPOSE_REP2", justification = "Design intent")
      public RandomAccessFileReader(@NotNull RandomAccessFile file, int baseOffset) throws IOException
      {
          if (file == null)
              throw new NullPointerException();
  
          _file = file;
          _baseOffset = baseOffset;
          _length = _file.length();
      }
  
      @Override
      public int toUnshiftedOffset(int localOffset)
      {
          return localOffset + _baseOffset;
      }
  
      @Override
      public long getLength()
      {
          return _length;
      }
  
      @Override
      public byte getByte(int index) throws IOException
      {
          if (index != _currentIndex)
              seek(index);
  
          final int b = _file.read();
          if (b < 0)
              throw new BufferBoundsException("Unexpected end of file encountered.");
          assert (b <= 0xff);
          _currentIndex++;
          return (byte)b;
      }
  
      @Override
      @NotNull
      public byte[] getBytes(int index, int count) throws IOException
      {
          validateIndex(index, count);
  
          if (index != _currentIndex)
              seek(index);
  
          byte[] bytes = new byte[count];
          final int bytesRead = _file.read(bytes);
          _currentIndex += bytesRead;
          if (bytesRead != count)
              throw new BufferBoundsException("Unexpected end of file encountered.");
          return bytes;
      }
  
      private void seek(final int index) throws IOException
      {
          if (index == _currentIndex)
              return;
  
          _file.seek(index);
          _currentIndex = index;
      }
  
      @Override
      protected boolean isValidIndex(int index, int bytesRequested) throws IOException
      {
          return bytesRequested >= 0
                  && index >= 0
                  && (long)index + (long)bytesRequested - 1L < _length;
      }
  
      @Override
      protected void validateIndex(final int index, final int bytesRequested) throws IOException
      {
          if (!isValidIndex(index, bytesRequested))
              throw new BufferBoundsException(index, bytesRequested, _length);
      }
  }
  