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On 10 December 2015 at 04:22, Cezary H. Noweta <> wrote:
> On 2015-12-10 04:49, Cezary H. Noweta wrote:
>>>> On Wed, Dec 9, 2015 at 9:29 PM, Jay Carlson <> wrote:
>>>>> Given a string where is_utf8(s) is false, it might be nice to be
>>>>> able to find the byte offset of the first non-UTF-8 sequence.
>> For Jay's idea: (1) let utf8.validate() return:
>> str false --> if there was not ill-formed (number 0 is not false)
>> str number --> number of first invalid byte (in src str)
>>             --> if there was ill-formed
>> and/or (2) third parameter (flags in one integer parameter?) stoponerror
>> - if somebody want to write his own make_safe, then it is good idea to
>> have the first well-formed part of string instead of a whole
>> validificated string.
> OK - now the function returns:
> str false --> if every thing is ok
> str number --> if there was an error;
>                number is position in the source string
>                of invalid character

Minor detail, but using "false" to indicate no-error is something I've
never seen in Lua APIs. (It's common in C to mean 0 = OK, but `false`
as OK in Lua strikes me as strange). I think nil would be more
idiomatic there, to indicate "absence" of the error position. And you
could still do:

local s, errpos = utf8.validate("bla")
if errpos then
   -- got an error position


It would be nice if this function was implemented as part of a
standalone module that could be deployed separately, instead of
injecting into the standard `utf8` table. (It would be nicer for
distributing with LuaRocks, too). utf8check, maybe?

Also, "sanitize" sounds like a good name for the function itself.

-- Hisham