/*
    * Copyright (C) 2005-2015 Schlichtherle IT Services.
    * All rights reserved. Use is subject to license terms.
    */
   package net.java.truevfs.comp.zip;
   
   import static java.lang.System.arraycopy;
   import javax.annotation.CheckForNull;
   import javax.annotation.concurrent.NotThreadSafe;
  
  /**
   * Default implementation for an Extra Field in a Local or Central Header of a
   * ZIP file.
   *
   * @author Christian Schlichtherle
   */
  @NotThreadSafe
  final class DefaultExtraField extends ExtraField {
  
      private final short headerId;
      private @CheckForNull byte[] data;
  
      /**
       * Constructs a new extra field.
       *
       * @param  headerId an unsigned short integer (two bytes) indicating the
       *         type of the extra field.
       */
      DefaultExtraField(final int headerId) {
          assert UShort.check(headerId);
          this.headerId = (short) headerId;
      }
  
      @Override
      int getHeaderId() {
          return headerId & UShort.MAX_VALUE;
      }
  
      @Override
      int getDataSize() {
          final byte[] data = this.data;
          return null != data ? data.length : 0;
      }
  
      @Override
      void readFrom(final byte[] buf, final int off, final int len) {
          assert UShort.check(len);
          arraycopy(buf, off, this.data = new byte[len], 0, len);
      }
  
      @Override
      void writeTo(byte[] buf, int off) {
          final byte[] src = this.data;
          if (null != src) arraycopy(src, 0, buf, off, src.length);
      }
  }