}
    return new String(dest, 0, destIndex);
  }

  /**
   * Returns the Unicode code point of the character at the given index.
   *
   * <p>Unlike {@link Character#codePointAt(CharSequence, int)} or {@link String#codePointAt(int)}
   * this method will never fail silently when encountering an invalid surrogate pair.
   *
   * <p>The behaviour of this method is as follows:
   *
   * <ol>

  unicodeAllowed: Boolean,
  charset: Charset?,
) {
  var encodedCharBuffer: Buffer? = null // Lazily allocated.
  var codePoint: Int
  var i = pos
  while (i < limit) {
    codePoint = input.codePointAt(i)
    if (alreadyEncoded &&
      (
        codePoint == '\t'.code ||
          codePoint == '\n'.code ||
          codePoint == '\u000c'.code ||
          codePoint == '\r'.code
      )
    ) {

    // Ordinarily we'd use something like i += Character.charCount(string.codePointAt(i)) here. But
    // we can get away with i++ because the whole point of this method is to return false if we find
    // a code point that doesn't fit in a char.
    for (int i = 0; i < string.length(); i++) {
      if (string.codePointAt(i) > 0xffff) {
        return false;
      }
    }
    return true;
  }

    // Ordinarily we'd use something like i += Character.charCount(string.codePointAt(i)) here. But
    // we can get away with i++ because the whole point of this method is to return false if we find
    // a code point that doesn't fit in a char.
    for (int i = 0; i < string.length(); i++) {
      if (string.codePointAt(i) > 0xffff) {
        return false;
      }
    }
    return true;
  }

          buffer |= charToThreeUtf8Bytes(c) << shift;
          shift += 24;
          len += 3;
        } else {
          int codePoint = Character.codePointAt(input, i);
          if (codePoint == c) {
            // not a valid code point; let the JDK handle invalid Unicode
            return hashBytes(input.toString().getBytes(charset));
          }
          i++;

        .isEqualTo("\0HELLO \uD800\uDC00 WORLD!\n");
  }

  public void testCodePointAt_indexOutOfBoundsException() {
    assertThrows(
        IndexOutOfBoundsException.class, () -> UnicodeEscaper.codePointAt("Testing...", 4, 2));
  }

  private static String escapeAsString(Escaper e, String s) {
    return e.escape(s);
  }

        // We can't use Character.isSurrogate(c) here and below because of GWT.
        if (MIN_SURROGATE <= c && c <= MAX_SURROGATE) {
          // Check that we have a well-formed surrogate pair.
          if (Character.codePointAt(sequence, i) == c) {
            throw new IllegalArgumentException(unpairedSurrogateMsg(i));
          }
          i++;
        }
      }
    }
    return utf8Length;
  }

  /**

        // We can't use Character.isSurrogate(c) here and below because of GWT.
        if (MIN_SURROGATE <= c && c <= MAX_SURROGATE) {
          // Check that we have a well-formed surrogate pair.
          if (Character.codePointAt(sequence, i) == c) {
            throw new IllegalArgumentException(unpairedSurrogateMsg(i));
          }
          i++;
        }
      }
    }
    return utf8Length;
  }

  /**

            return QueryBuilders.matchPhraseQuery(f, text);
        }

        final UnicodeBlock block = UnicodeBlock.of(text.codePointAt(0));
        if (block == UnicodeBlock.CJK_UNIFIED_IDEOGRAPHS //
                || block == UnicodeBlock.HIRAGANA //
                || block == UnicodeBlock.KATAKANA //

        fst.getFirstArc(scratchArc);
        BytesRef matchOutput = null;

        int index = 0;
        while (start + index < src.length) {
            final int codePoint = Character.codePointAt(src, start + index, src.length);
            if (fst.findTargetArc(ignoreCase ? Character.toLowerCase(codePoint) : codePoint, scratchArc, scratchArc, fstReader) == null) {
                return matchOutput;
            }