static void handleFourBytes()

in datasketches-memory-java8/src/main/java/org/apache/datasketches/memory/internal/Utf8.java [552:576]

• 18 lines of code
• 5 McCabe index (conditional complexity)

    static void handleFourBytes(
        final byte byte1, final byte byte2, final byte byte3, final byte byte4,
        final Appendable dst)
        throws IOException, Utf8CodingException {
      if (isNotTrailingByte(byte2)
          // Check that 1 <= plane <= 16. Tricky optimized form of:
          //   valid 4-byte leading byte?
          // if (byte1 > (byte) 0xF4 ||
          //   overlong? 4 most significant bits must not all be zero
          //     byte1 == (byte) 0xF0 && byte2 < (byte) 0x90 ||
          //   codepoint larger than the highest code point (U+10FFFF)?
          //     byte1 == (byte) 0xF4 && byte2 > (byte) 0x8F)
          || ((((byte1 << 28) + (byte2 - (byte) 0x90)) >> 30) != 0)
          || isNotTrailingByte(byte3)
          || isNotTrailingByte(byte4)) {
        final byte[] out = new byte[] { byte1, byte2, byte3, byte4 };
        throw Utf8CodingException.illegalUtf8DecodeByteSequence(out);
      }
      final int codepoint = ((byte1 & 0x07) << 18)
          | (trailingByteValue(byte2) << 12)
          | (trailingByteValue(byte3) << 6)
          | trailingByteValue(byte4);
      dst.append(DecodeUtil.highSurrogate(codepoint));
      dst.append(DecodeUtil.lowSurrogate(codepoint));
    }