}

  static CharMatcher from(BitSet chars, String description) {
    // Compute the filter.
    long filter = 0;
    int size = chars.cardinality();
    boolean containsZero = chars.get(0);
    // Compute the hash table.
    char[] table = new char[chooseTableSize(size)];
    int mask = table.length - 1;
    for (int c = chars.nextSetBit(0); c != -1; c = chars.nextSetBit(c + 1)) {

          private final char[] unknown = new char[] {'?'};

          @Override
          protected char[] escapeUnsafe(char c) {
            return unknown;
          }
        };
    EscaperAsserts.assertBasic(replacingEscaper);

    // Replacements are applied first regardless of whether the character is in
    // the safe range or not ('&' is a safe char while '\t' and '\n' are not).
    assertEquals(

    final String allMatchingChars = allMatchingChars(bitSet);
    final char[] result = new char[STRING_LENGTH];
    // Fill with matching chars.
    for (int i = 0; i < result.length; i++) {
      result[i] = allMatchingChars.charAt(random.nextInt(allMatchingChars.length()));
    }
    // Replace some of chars by non-matching.
    int remaining = (int) ((100 - percentMatching) * result.length / 100.0 + 0.5);

   *
   * @return the replacement characters, or {@code null} if no escaping was required
   */
  @Override
  @CheckForNull
  protected final char[] escape(int cp) {
    if (cp < replacementsLength) {
      char[] chars = replacements[cp];
      if (chars != null) {
        return chars;
      }
    }
    if (cp >= safeMin && cp <= safeMax) {
      return null;
    }
    return escapeUnsafe(cp);
  }

          protected void handleLine(String line, String end) {
            lines.add(line + end);
          }
        };
    char[] chars = input.toCharArray();
    int off = 0;
    while (off < chars.length) {
      int len = Math.min(chars.length, off + chunk) - off;
      lineBuf.add(chars, off, len);
      off += len;
    }
    lineBuf.finish();
    return lines;
  }

  }

  public void testCharsIgnored() {
    for (char c : IGNORED.toCharArray()) {
      String str = String.valueOf(c);
      assertEquals(str, c, Ascii.toLowerCase(c));
      assertEquals(str, c, Ascii.toUpperCase(c));
      assertFalse(str, Ascii.isLowerCase(c));
      assertFalse(str, Ascii.isUpperCase(c));
    }
  }

  public void testCharsLower() {
    for (char c : LOWER.toCharArray()) {
      String str = String.valueOf(c);

    int i = 0;

    // This loop optimizes for pure ASCII.
    while (i < utf16Length && sequence.charAt(i) < 0x80) {
      i++;
    }

    // This loop optimizes for chars less than 0x800.
    for (; i < utf16Length; i++) {
      char c = sequence.charAt(i);
      if (c < 0x800) {
        utf8Length += ((0x7f - c) >>> 31); // branch free!
      } else {
        utf8Length += encodedLengthGeneral(sequence, i);

  // that are considered authoritative for the behavior of that escaper.

  static final String URL_FORM_PARAMETER_OTHER_SAFE_CHARS = "-_.*";

  static final String URL_PATH_OTHER_SAFE_CHARS_LACKING_PLUS =
      "-._~" // Unreserved characters.
          + "!$'()*,;&=" // The subdelim characters (excluding '+').
          + "@:"; // The gendelim characters permitted in paths.

    // read char by char
    CharSequenceReader reader = new CharSequenceReader(charSequence);
    for (int i = 0; i < expected.length(); i++) {
      assertEquals(expected.charAt(i), reader.read());
    }
    assertFullyRead(reader);

    // read all to one array
    reader = new CharSequenceReader(charSequence);
    char[] buf = new char[expected.length()];

    }
  }

  public void testUtf8() {
    char[] charsA = new char[128];
    char[] charsB = new char[128];

    for (int i = 0; i < charsA.length; i++) {
      if (i < 100) {
        charsA[i] = 'a';
        charsB[i] = 'a';
      } else {
        // Both two-byte characters, but must be different
        charsA[i] = (char) (0x0180 + i);
        charsB[i] = (char) (0x0280 + i);
      }
    }