when {
            b == 0x80 -> {
              // 10000000
              throw IOException("index == 0")
            }
            b and 0x80 == 0x80 -> {
              // 1NNNNNNN
              val index = readInt(b, PREFIX_7_BITS)
              readIndexedHeader(index - 1)
            }
            b == 0x40 -> {
              // 01000000

      get() {
        val b3bit8 = mappedTo[0] and 0x80 != 0
        return if (b3bit8) 123 else 122
      }

    val b2: Int
      get() = mappedTo[0] and 0x7f
  }

  data class Inline2(
    override val rangeStart: Int,
    private val mappedTo: ByteString,
  ) : MappedRange {
    val b1: Int
      get() {
        val b2bit8 = mappedTo[0] and 0x80 != 0
        val b3bit8 = mappedTo[1] and 0x80 != 0

      // Encode '+' as '%2B' since we permit ' ' to be encoded as either '+' or '%20'.
      writeUtf8(if (alreadyEncoded) "+" else "%2B")
    } else if (codePoint < 0x20 ||
      codePoint == 0x7f ||
      codePoint >= 0x80 &&
      !unicodeAllowed ||
      codePoint.toChar() in encodeSet ||
      codePoint == '%'.code &&
      (!alreadyEncoded || strict && !input.isPercentEncoded(i, limit))
    ) {

	for _, c := range s {
		if c >= 0x80 || c == 0x00 {
			return false
		}
	}
	return true
}

// toASCII converts the input to an ASCII C-style string.
// This is a best effort conversion, so invalid characters are dropped.
func toASCII(s string) string {
	if isASCII(s) {
		return s
	}
	b := make([]byte, 0, len(s))
	for _, c := range s {
		if c < 0x80 && c != 0x00 {
			b = append(b, byte(c))
		}
	}

        sink.writeByte(ranges[rangesIndex + 2].code)
        sink.writeByte(ranges[rangesIndex + 3].code or 0x80)
      }
      127 -> {
        // Mapped inline to the sequence: [b2a, b3a].
        sink.writeByte(ranges[rangesIndex + 2].code or 0x80)
        sink.writeByte(ranges[rangesIndex + 3].code or 0x80)
      }
      else -> error("unexpected rangesIndex for $codePoint")
    }

    return true
  }

0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75, 0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84, 0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf, 0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8, 0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2, 0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97,...

          return 0x80;
        } else if (userFriendly.matches("(?i)(?:French|Latin|Western.*European)")) {
          // Mostly 1-byte UTF-8 sequences, mixed with occasional 2-byte
          // sequences - "Western European" text
          return 0x90;
        } else if (userFriendly.matches("(?i)(?:Branch.*Prediction.*Hostile)")) {
          // Defeat branch predictor for: c < 0x80 ; branch taken 50% of the time.

	// map header, size 2
	// string "LimitInBytesPerSecond"
	o = append(o, 0x82, 0xb5, 0x4c, 0x69, 0x6d, 0x69, 0x74, 0x49, 0x6e, 0x42, 0x79, 0x74, 0x65, 0x73, 0x50, 0x65, 0x72, 0x53, 0x65, 0x63, 0x6f, 0x6e, 0x64)
	o = msgp.AppendInt64(o, z.LimitInBytesPerSecond)
	// string "CurrentBandwidthInBytesPerSecond"

    assertThat(Buffer().writeUtf8("Слава Україні!").isProbablyUtf8(16L)).isTrue()
    assertThat(Buffer().writeByte(0x80).isProbablyUtf8(16L)).isTrue()
    assertThat(Buffer().writeByte(0x00).isProbablyUtf8(16L)).isFalse()
    assertThat(Buffer().writeByte(0xc0).isProbablyUtf8(16L)).isFalse()
  }

  @Test fun doesNotConsumeBuffer() {
    val buffer = Buffer()
    buffer.writeUtf8("hello ".repeat(1024))

0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75, 0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84, 0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf, 0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8, 0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2, 0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97,...