// TODO: track which type of frame & with which flags was sent
	// last. Then return an error (unless AllowIllegalWrites) if
	// we're in the middle of a header block and a
	// non-Continuation or Continuation on a different stream is
	// attempted to be written.

	logReads, logWrites bool

	debugFramer       *http2Framer // only use for logging written writes
	debugFramerBuf    *bytes.Buffer

		c1 := s[1]
		if c1 < 0x80 || 0xC0 <= c1 {
			return 0, 1 // Illegal UTF-8: not a continuation byte.
		}
		return t.lookupValue(uint32(i), c1), 2
	case c0 < 0xF0: // 3-byte UTF-8
		if len(s) < 3 {
			return 0, 0
		}
		i := nfcIndex[c0]
		c1 := s[1]
		if c1 < 0x80 || 0xC0 <= c1 {
			return 0, 1 // Illegal UTF-8: not a continuation byte.
		}
		o := uint32(i)<<6 + uint32(c1)
		i = nfcIndex[o]

		c1 := s[1]
		if c1 < 0x80 || 0xC0 <= c1 {
			return 0, 1 // Illegal UTF-8: not a continuation byte.
		}
		return t.lookupValue(uint32(i), c1), 2
	case c0 < 0xF0: // 3-byte UTF-8
		if len(s) < 3 {
			return 0, 0
		}
		i := nfcIndex[c0]
		c1 := s[1]
		if c1 < 0x80 || 0xC0 <= c1 {
			return 0, 1 // Illegal UTF-8: not a continuation byte.
		}
		o := uint32(i)<<6 + uint32(c1)
		i = nfcIndex[o]

		c1 := s[1]
		if c1 < 0x80 || 0xC0 <= c1 {
			return 0, 1 // Illegal UTF-8: not a continuation byte.
		}
		return t.lookupValue(uint32(i), c1), 2
	case c0 < 0xF0: // 3-byte UTF-8
		if len(s) < 3 {
			return 0, 0
		}
		i := nfcIndex[c0]
		c1 := s[1]
		if c1 < 0x80 || 0xC0 <= c1 {
			return 0, 1 // Illegal UTF-8: not a continuation byte.
		}
		o := uint32(i)<<6 + uint32(c1)
		i = nfcIndex[o]

		c1 := s[1]
		if c1 < 0x80 || 0xC0 <= c1 {
			return 0, 1 // Illegal UTF-8: not a continuation byte.
		}
		return t.lookupValue(uint32(i), c1), 2
	case c0 < 0xF0: // 3-byte UTF-8
		if len(s) < 3 {
			return 0, 0
		}
		i := nfcIndex[c0]
		c1 := s[1]
		if c1 < 0x80 || 0xC0 <= c1 {
			return 0, 1 // Illegal UTF-8: not a continuation byte.
		}
		o := uint32(i)<<6 + uint32(c1)
		i = nfcIndex[o]

		c1 := s[1]
		if c1 < 0x80 || 0xC0 <= c1 {
			return 0, 1 // Illegal UTF-8: not a continuation byte.
		}
		return t.lookupValue(uint32(i), c1), 2
	case c0 < 0xF0: // 3-byte UTF-8
		if len(s) < 3 {
			return 0, 0
		}
		i := nfcIndex[c0]
		c1 := s[1]
		if c1 < 0x80 || 0xC0 <= c1 {
			return 0, 1 // Illegal UTF-8: not a continuation byte.
		}
		o := uint32(i)<<6 + uint32(c1)
		i = nfcIndex[o]

		c1 := s[1]
		if c1 < 0x80 || 0xC0 <= c1 {
			return 0, 1 // Illegal UTF-8: not a continuation byte.
		}
		return t.lookupValue(uint32(i), c1), 2
	case c0 < 0xF0: // 3-byte UTF-8
		if len(s) < 3 {
			return 0, 0
		}
		i := nfcIndex[c0]
		c1 := s[1]
		if c1 < 0x80 || 0xC0 <= c1 {
			return 0, 1 // Illegal UTF-8: not a continuation byte.
		}
		o := uint32(i)<<6 + uint32(c1)
		i = nfcIndex[o]

		c1 := s[1]
		if c1 < 0x80 || 0xC0 <= c1 {
			return 0, 1 // Illegal UTF-8: not a continuation byte.
		}
		return t.lookupValue(uint32(i), c1), 2
	case c0 < 0xF0: // 3-byte UTF-8
		if len(s) < 3 {
			return 0, 0
		}
		i := nfcIndex[c0]
		c1 := s[1]
		if c1 < 0x80 || 0xC0 <= c1 {
			return 0, 1 // Illegal UTF-8: not a continuation byte.
		}
		o := uint32(i)<<6 + uint32(c1)
		i = nfcIndex[o]

		c1 := s[1]
		if c1 < 0x80 || 0xC0 <= c1 {
			return 0, 1 // Illegal UTF-8: not a continuation byte.
		}
		return t.lookupValue(uint32(i), c1), 2
	case c0 < 0xF0: // 3-byte UTF-8
		if len(s) < 3 {
			return 0, 0
		}
		i := nfcIndex[c0]
		c1 := s[1]
		if c1 < 0x80 || 0xC0 <= c1 {
			return 0, 1 // Illegal UTF-8: not a continuation byte.
		}
		o := uint32(i)<<6 + uint32(c1)
		i = nfcIndex[o]

		c1 := s[1]
		if c1 < 0x80 || 0xC0 <= c1 {
			return 0, 1 // Illegal UTF-8: not a continuation byte.
		}
		return t.lookupValue(uint32(i), c1), 2
	case c0 < 0xF0: // 3-byte UTF-8
		if len(s) < 3 {
			return 0, 0
		}
		i := nfcIndex[c0]
		c1 := s[1]
		if c1 < 0x80 || 0xC0 <= c1 {
			return 0, 1 // Illegal UTF-8: not a continuation byte.
		}
		o := uint32(i)<<6 + uint32(c1)
		i = nfcIndex[o]