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Subject: Re: [SG16-Unicode] Convert between std::u8string and std::string
From: Tom Honermann (tom_at_[hidden])
Date: 2019-05-03 10:19:43


On 5/3/19 7:12 AM, Lyberta wrote:
> So GCC 9 has been released and I'm starting migration to char8_t. The
> first question is how to print std::u8string? Since std::cout works in
> execution character set I need a way to convert string from UTF-8 to ECS.
I wish I had a better suggestion for you then std::c8rtomb. JeanHeyd is
working on a proposal for modern transcoding interfaces.
>
> It looks like the only way is to use std::c8rtomb but the API is very
> cryptic and I don't understand it. Can someone provide an example code?

As far as I know, no one has actually implemented std::c8rtomb yet.  It
has been on my todo list for a long time to contribute an implementation
to glibc, but I haven't found the time yet.

c8rtomb is intended to match the existing c16rtomb and c32rtomb
functions, so inherits design and wording from them.  The wording in the
C++ standard for c8rtomb is a lightly edited copy of the C standard's
wording for c16rtomb.  That wording is, well, it could be improved.  A
lot.  I intentionally chose to keep it aligned with the C standard so as
not to cause confusion for implementors (presumably, they have already
come to an understanding with C's wording).

I suggest looking at the examples for c16rtomb on cppreference.com.
- https://en.cppreference.com/w/cpp/string/multibyte/c16rtomb

Tom.

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