def utf8.n

bend-kit-json@0.7.0.0 · json.bend:260

import Base

260# RFC 3629 §4: overlong forms, surrogates, and code points past U+10FFFF are invalid, width 0.
261def utf8.n(+b0: U32, +b1: U32, +b2: U32, +b3: U32) -> Cp:
262  +x1 = (b1 .&. 63 : U32)
263  +x2 = (b2 .&. 63 : U32)
264  +x3 = (b3 .&. 63 : U32)
265  +c2 = (((b0 .&. 31) << 6n) .|. x1 : U32)
266  +c3 = ((((b0 .&. 15) << 12n) .|. (x1 << 6n)) .|. x2 : U32)
267  +c4 = (((((b0 .&. 7) << 18n) .|. (x1 << 12n)) .|. (x2 << 6n)) .|. x3 : U32)
268  +ok2 = U32.is_le(192, b0) && U32.is_lt(b0, 224) && cont(b1) && U32.is_le(128, c2)
269  +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))
270  +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)
271  Bool.pick(Cp, ok2, Cp{c2, 2}, Bool.pick(Cp, ok3, Cp{c3, 3}, Bool.pick(Cp, ok4, Cp{c4, 4}, Cp{0, 0})))