VALID_UTF8_BYTE_SEQUENCES = {
  [0x00] => '\u{0000}',
  [0x7F] => '\u{007F}',

  [0xC2, 0x80] => '\u{0080}',
  [0xC2, 0xBF] => '\u{00BF}',
  [0xDF, 0x80] => '\u{07C0}',
  [0xDF, 0xBF] => '\u{07FF}',

  [0xE0, 0xA0, 0x80] => '\u{0800}',
  [0xE0, 0xA0, 0xBF] => '\u{083F}',
  [0xE0, 0xBF, 0x80] => '\u{0FC0}',
  [0xE0, 0xBF, 0xBF] => '\u{0FFF}',
  [0xE1, 0x80, 0x80] => '\u{1000}',
  [0xE1, 0x80, 0xBF] => '\u{103F}',
  [0xE1, 0x9F, 0x80] => '\u{17C0}',
  [0xE1, 0x9F, 0xBF] => '\u{17FF}',
  [0xE1, 0xA0, 0x80] => '\u{1800}',
  [0xE1, 0xA0, 0xBF] => '\u{183F}',
  [0xE1, 0xBF, 0x80] => '\u{1FC0}',
  [0xE1, 0xBF, 0xBF] => '\u{1FFF}',
  [0xED, 0x80, 0x80] => '\u{D000}',
  [0xED, 0x80, 0xBF] => '\u{D03F}',
  [0xED, 0x9F, 0x80] => '\u{D7C0}',
  [0xED, 0x9F, 0xBF] => '\u{D7FF}',
  [0xEF, 0x80, 0x80] => '\u{F000}',
  [0xEF, 0x80, 0xBF] => '\u{F03F}',
  [0xEF, 0x9F, 0x80] => '\u{F7C0}',
  [0xEF, 0x9F, 0xBF] => '\u{F7FF}',
  [0xEF, 0xA0, 0x80] => '\u{F800}',
  [0xEF, 0xA0, 0xBF] => '\u{F83F}',
  [0xEF, 0xBF, 0x80] => '\u{FFC0}',
  [0xEF, 0xBF, 0xBF] => '\u{FFFF}',

  [0xF0, 0x90, 0x80, 0x80] => '\u{10000}',
  [0xF0, 0x90, 0x80, 0xBF] => '\u{1003F}',
  [0xF0, 0x90, 0xBF, 0x80] => '\u{10FC0}',
  [0xF0, 0x90, 0xBF, 0xBF] => '\u{10FFF}',
  [0xF0, 0xBF, 0x80, 0x80] => '\u{3F000}',
  [0xF0, 0xBF, 0x80, 0xBF] => '\u{3F03F}',
  [0xF0, 0xBF, 0xBF, 0x80] => '\u{3FFC0}',
  [0xF0, 0xBF, 0xBF, 0xBF] => '\u{3FFFF}',
  [0xF1, 0x80, 0x80, 0x80] => '\u{40000}',
  [0xF1, 0x80, 0x80, 0xBF] => '\u{4003F}',
  [0xF1, 0x80, 0xBF, 0x80] => '\u{40FC0}',
  [0xF1, 0x80, 0xBF, 0xBF] => '\u{40FFF}',
  [0xF1, 0x8F, 0x80, 0x80] => '\u{4F000}',
  [0xF1, 0x8F, 0x80, 0xBF] => '\u{4F03F}',
  [0xF1, 0x8F, 0xBF, 0x80] => '\u{4FFC0}',
  [0xF1, 0x8F, 0xBF, 0xBF] => '\u{4FFFF}',
  [0xF3, 0x90, 0x80, 0x80] => '\u{D0000}',
  [0xF3, 0xBF, 0xBF, 0xBF] => '\u{FFFFF}',
  [0xF4, 0x80, 0x80, 0x80] => '\u{100000}',
  [0xF4, 0x80, 0x80, 0xBF] => '\u{10003F}',
  [0xF4, 0x80, 0xBF, 0x80] => '\u{100FC0}',
  [0xF4, 0x80, 0xBF, 0xBF] => '\u{100FFF}',
  [0xF4, 0x8F, 0x80, 0x80] => '\u{10F000}',
  [0xF4, 0x8F, 0xBF, 0xBF] => '\u{10FFFF}',
}

INVALID_UTF8_BYTE_SEQUENCES = [
  # non-starters
  [0x80],
  [0x8F],
  [0x90],
  [0x9F],
  [0xA0],
  [0xAF],
  [0xB0],
  [0xBF],
  [0xFE],
  [0xFF],

  # incomplete, 2-byte
  [0xC2],
  [0xC2, 0x00],
  [0xC2, 0xC2],

  # overlong, 2-byte
  [0xC0, 0x80],
  [0xC1, 0xBF],

  # incomplete, 3-byte
  [0xE1],
  [0xE1, 0x00],
  [0xE1, 0xC2],
  [0xE1, 0x80],
  [0xE1, 0x80, 0x00],
  [0xE1, 0x80, 0xC2],

  # overlong, 3-byte
  [0xE0, 0x80, 0x80],
  [0xE0, 0x9F, 0xBF],

  # surrogate pairs
  [0xED, 0xA0, 0x80],
  [0xED, 0xBF, 0xBF],

  # incomplete, 4-byte
  [0xF1],
  [0xF1, 0x00],
  [0xF1, 0xC2],
  [0xF1, 0x80],
  [0xF1, 0x80, 0x00],
  [0xF1, 0x80, 0xC2],
  [0xF1, 0x80, 0x80],
  [0xF1, 0x80, 0x80, 0x00],
  [0xF1, 0x80, 0x80, 0xC2],

  # overlong, 4-byte
  [0xF0, 0x80, 0x80, 0x80],
  [0xF0, 0x8F, 0xBF, 0xBF],

  # upper boundary, 4-byte
  [0xF4, 0x90, 0x80, 0x80],
  [0xF5],

  # 5-byte (obsolete)
  [0xF8],
  [0xF8, 0x80, 0x80, 0x80, 0x80],

  # 6-byte (obsolete)
  [0xFC],
  [0xFC, 0x80, 0x80, 0x80, 0x80, 0x80],
]