/** Parses an {@code InnerClasses} attribute. */
  private Attribute innerClasses(
      DirectClassFile cf, int offset, int length, ParseObserver observer) {
    if (length < 2) {
      return throwSeverelyTruncated();
    }

    ByteArray bytes = cf.getBytes();
    ConstantPool pool = cf.getConstantPool();
    int count = bytes.getUnsignedShort(offset); // number_of_classes

    if (observer != null) {
      observer.parsed(bytes, offset, 2, "number_of_classes: " + Hex.u2(count));
    }

    offset += 2;
    length -= 2;

    if (length != (count * 8)) {
      throwBadLength((count * 8) + 2);
    }

    InnerClassList list = new InnerClassList(count);

    for (int i = 0; i < count; i++) {
      int innerClassIdx = bytes.getUnsignedShort(offset);
      int outerClassIdx = bytes.getUnsignedShort(offset + 2);
      int nameIdx = bytes.getUnsignedShort(offset + 4);
      int accessFlags = bytes.getUnsignedShort(offset + 6);
      CstType innerClass = (CstType) pool.get(innerClassIdx);
      CstType outerClass = (CstType) pool.get0Ok(outerClassIdx);
      CstString name = (CstString) pool.get0Ok(nameIdx);
      list.set(i, innerClass, outerClass, name, accessFlags);
      if (observer != null) {
        observer.parsed(
            bytes, offset, 2, "inner_class: " + DirectClassFile.stringOrNone(innerClass));
        observer.parsed(
            bytes, offset + 2, 2, "  outer_class: " + DirectClassFile.stringOrNone(outerClass));
        observer.parsed(bytes, offset + 4, 2, "  name: " + DirectClassFile.stringOrNone(name));
        observer.parsed(
            bytes, offset + 6, 2, "  access_flags: " + AccessFlags.innerClassString(accessFlags));
      }
      offset += 8;
    }

    list.setImmutable();
    return new AttInnerClasses(list);
  }
  /** Parses an {@code EnclosingMethod} attribute. */
  private Attribute enclosingMethod(
      DirectClassFile cf, int offset, int length, ParseObserver observer) {
    if (length != 4) {
      throwBadLength(4);
    }

    ByteArray bytes = cf.getBytes();
    ConstantPool pool = cf.getConstantPool();

    int idx = bytes.getUnsignedShort(offset);
    CstType type = (CstType) pool.get(idx);

    idx = bytes.getUnsignedShort(offset + 2);
    CstNat method = (CstNat) pool.get0Ok(idx);

    Attribute result = new AttEnclosingMethod(type, method);

    if (observer != null) {
      observer.parsed(bytes, offset, 2, "class: " + type);
      observer.parsed(bytes, offset + 2, 2, "method: " + DirectClassFile.stringOrNone(method));
    }

    return result;
  }