diff options
| -rw-r--r-- | users/sterni/nix/utf8/default.nix | 31 |
1 files changed, 14 insertions, 17 deletions
diff --git a/users/sterni/nix/utf8/default.nix b/users/sterni/nix/utf8/default.nix index b3185d9743b5..0c6e7d940083 100644 --- a/users/sterni/nix/utf8/default.nix +++ b/users/sterni/nix/utf8/default.nix @@ -38,9 +38,7 @@ let Based on table 3-7. from The Unicode Standard, Version 13.0, section 3.9. - Throws if the first byte is invalid. - - Type: integer -> integer -> (integer -> bool) + Type: integer -> integer -> integer -> bool */ wellFormedByte = # first byte's integer value @@ -49,16 +47,8 @@ let pos: let defaultRange = int.inRange 128 191; - in - # The first byte is either ASCII which requires no checks - # or we automatically check it when we check the subsequent - # bytes. The downside is that this may generate bad error - # messages in very rare cases. - if pos == 0 - then lib.const true - else if pos > 1 # 3rd and 4th byte have only one validity rule - then defaultRange - else assert pos == 1; flow.switch first [ + + secondBytePredicate = flow.switch first [ [ (int.inRange 194 223) defaultRange ] # C2..DF [ 224 (int.inRange 160 191) ] # E0 [ (int.inRange 225 236) defaultRange ] # E1..EC @@ -67,12 +57,19 @@ let [ 240 (int.inRange 144 191) ] # F0 [ (int.inRange 241 243) defaultRange ] # F1..F3 [ 244 (int.inRange 128 143) ] # F4 - [ - (fun.const true) - (builtins.throw "Invalid first byte ${int.toHex first}") - ] + [ (fun.const true) null ] ]; + firstBytePredicate = byte: assert first == byte; + first < 128 || secondBytePredicate != null; + in + # Either ASCII or in one of the byte ranges of Table 3-6. + if pos == 0 then firstBytePredicate + # return predicate according to Table 3-6. + else if pos == 1 then assert secondBytePredicate != null; secondBytePredicate + # 3rd and 4th byte have only one validity rule + else defaultRange; + /* Iteration step for decoding an UTF-8 byte sequence. It decodes incrementally, i. e. it has to be fed one byte at a time and then returns either a |