* general way.
 *
 * <p>A good example of usage of this class is for HTML escaping where the replacement array
 * contains information about the named HTML entities such as {@code &amp;} and {@code &quot;} while
 * {@link #escapeUnsafe} is overridden to handle general escaping of the form {@code &#NNNNN;}.
 *
 * <p>The size of the data structure used by {@link ArrayBasedUnicodeEscaper} is proportional to the

 * array contains information about special ASCII characters such as {@code \\t} and {@code \\n}
 * while {@link #escapeUnsafe} is overridden to handle general escaping of the form {@code \\uxxxx}.
 *
 * <p>The size of the data structure used by {@link ArrayBasedCharEscaper} is proportional to the
 * highest valued character that requires escaping. For example a replacement map containing the

   * form parameter names and values</a>. Escaping is performed with the UTF-8 character encoding.
   * The caller is responsible for <a
   * href="https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#multipart-form-data">replacing
   * any unpaired carriage return or line feed characters with a CR+LF pair</a> on any non-file
   * inputs before escaping them with this escaper.
   *

 * elements' text contents. When possible, avoid manual escaping by using templating systems and
 * high-level APIs that provide autoescaping. For example, consider <a
 * href="http://www.xom.nu/">XOM</a>.
 *
 * <p><b>Note:</b> Currently the escapers provided by this class do not escape any characters
 * outside the ASCII character range. Unlike HTML escaping the XML escapers will not escape

 * most elements' text contents. When possible, avoid manual escaping by using templating
 * systems and high-level APIs that provide autoescaping.
 * One Google-authored templating system available for external use is <a
 * href="https://developers.google.com/closure/templates/">Closure Templates</a>.
 *
 * <p>HTML escaping is particularly tricky: For example, <a

@GwtCompatible
public final class Escapers {
  private Escapers() {}

  /**
   * Returns an {@link Escaper} that does no escaping, passing all character data through unchanged.
   */
  public static Escaper nullEscaper() {
    return NULL_ESCAPER;
  }

  // An Escaper that efficiently performs no escaping.
  // Extending CharEscaper (instead of Escaper) makes Escapers.compose() easier.
  private static final Escaper NULL_ESCAPER =

        // In regex, + means "one or more" of the previous character
        String wrongPattern = "(application/xhtml+xml|application/rdf+xml)";
        Pattern pattern = Pattern.compile(wrongPattern);

        // Without escaping, "application/xhtml+xml" does NOT match
        // because the pattern expects "one or more 'l'" followed by "xml"
        assertFalse(pattern.matcher("application/xhtml+xml").matches());

      ImmutableMap.of(
          '\n', "<newline>",
          '\t', "<tab>",
          '&', "<and>");

  public void testSafeRange() throws IOException {
    // Basic escaping of unsafe chars (wrap them in {,}'s)
    CharEscaper wrappingEscaper =
        new ArrayBasedCharEscaper(NO_REPLACEMENTS, 'A', 'Z') {
          @Override
          protected char[] escapeUnsafe(char c) {

        return value;
    }

    /**
     * Escapes special characters in a query string if escaping is enabled.
     * Replaces reserved characters with their escaped equivalents based on the Constants.RESERVED array.
     *
     * @param value the query string to escape
     * @return the escaped query string, or the original value if escaping is disabled
     */
    protected String escapeQuery(final String value) {
        if (!escape) {

    assertEscaping(xmlEscaper, "\uFFFD", '\uFFFF');

    assertWithMessage("0xFFFE is forbidden and should be replaced during escaping")
        .that(xmlEscaper.escape("[\ufffe]"))
        .isEqualTo("[\uFFFD]");
    assertWithMessage("0xFFFF is forbidden and should be replaced during escaping")
        .that(xmlEscaper.escape("[\uffff]"))
        .isEqualTo("[\uFFFD]");
  }