code: protected void blockTag() {
          int p = bp;
          try {
              nextChar();
              if (isIdentifierStart(ch)) {
                  String name = readTagName();
                  TagParser tp = tagParsers.get(name);
                  if (tp == null) {
                      blockContent();
                  } else {
                      switch (tp.getKind()) {
                          case BLOCK:
                              tp.parse(p);
                              return;
                          case INLINE:
                              return;
                      }
                  }
              }
              blockContent();
          } catch (ParseException e) {
              blockContent();
          }
      }
docs: Read a single block tag, including its content.
  Standard tags parse their content appropriately.
  Non-standard tags are represented by {@link UnknownBlockTag}.