Json.utf8.n: def of bend-kit-json@0.7.0.0
Import: import bend-kit-json@0.7.0.0/json.bend as Json
Lines 260-271 of bend-kit-json@0.7.0.0/json.bend: https://jend.leeeet.dev/read.txt?path=bend-kit-json@0.7.0.0/json.bend&start_line=260&end_line=271

import Base

# RFC 3629 §4: overlong forms, surrogates, and code points past U+10FFFF are invalid, width 0.
def utf8.n(+b0: U32, +b1: U32, +b2: U32, +b3: U32) -> Cp:
  +x1 = (b1 .&. 63 : U32)
  +x2 = (b2 .&. 63 : U32)
  +x3 = (b3 .&. 63 : U32)
  +c2 = (((b0 .&. 31) << 6n) .|. x1 : U32)
  +c3 = ((((b0 .&. 15) << 12n) .|. (x1 << 6n)) .|. x2 : U32)
  +c4 = (((((b0 .&. 7) << 18n) .|. (x1 << 12n)) .|. (x2 << 6n)) .|. x3 : U32)
  +ok2 = U32.is_le(192, b0) && U32.is_lt(b0, 224) && cont(b1) && U32.is_le(128, c2)
  +ok3 = U32.is_le(224, b0) && U32.is_lt(b0, 240) && cont(b1) && cont(b2) && U32.is_le(2048, c3) && (U32.is_lt(c3, 55296) || U32.is_lt(57343, c3))
  +ok4 = U32.is_le(240, b0) && U32.is_lt(b0, 248) && cont(b1) && cont(b2) && cont(b3) && U32.is_le(65536, c4) && U32.is_le(c4, 1114111)
  Bool.pick(Cp, ok2, Cp{c2, 2}, Bool.pick(Cp, ok3, Cp{c3, 3}, Bool.pick(Cp, ok4, Cp{c4, 4}, Cp{0, 0})))

Uses (11):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool.and
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool.or
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool.pick
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32.and
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32.is_le
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32.is_lt
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32.or
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32.shln
  https://jend.leeeet.dev/definition.txt?path=bend-kit-json@0.7.0.0/json.bend&name=Cp
  https://jend.leeeet.dev/definition.txt?path=bend-kit-json@0.7.0.0/json.bend&name=cont