Re: unicode and wide_text_io

[Dennis Lee Bieber <wlfraed@ix.netcom.com>]

On Sat, 30 Dec 2017 13:50:37 +0100, Björn Lundin <b.f.lundin@gmail.com>
declaimed the following:

>On 2017-12-28 23:36, Mehdi Saada wrote:
>> Myself:
>>> there are positions such as Wide_Character'Val(X) doesn't correspond to the Xth character in the UNICODE standard ??
>> Of course: Character'val(156) to 'val(255) are one byte long, whereas in UTF8 the corresponding code points are encoded with two bytes. Did I understood the lesson ?
>
>Yes - if it fits into 2 bytes. if not UTF-8 uses 3 and 4 bytes instead.
>So UTF-8 can use codepoints up to 32 bits (ca 4 billion)
>
>codepoint between
>1     -> 2**8  -1 = 1 byte

	Isn't that 0..2^7... Any byte with the MSB set is a multibyte code (and
number of MSB bits set before a 0 bit indicates how many bytes).

>2**8  -> 2**16 -1 = 2 bytes
>2**16 -> 2**24 -1 = 3 bytes
>2**24 -> 2**32 -1 = 4 bytes
>
>-- 
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/