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Converting an NVARCHAR string to a UTF-8 VARBINARY data block in pure Transact-SQL
create function [dbo].[ToUTF8](@s nvarchar(max))
returns varbinary(max)
declare @i int = 1, @n int = len(@s), @r varbinary(max) = 0x, @c int, @d varbinary(4)
while @i <= @n
set @c = unicode(substring(@s, @i, 1))
if (@c & 0xfc00) = 0xd800
set @i += 1
set @c = ((@c & 0x3ff) * 0x400) | 0x10000 | (unicode(substring(@s, @i, 1)) & 0x3ff)
if @c < 0x80
set @d = cast(@c as binary(1))
if @c >= 0x80 and @c < 0x800
set @d = cast(((@c * 4) & 0xFF00) | (@c & 0x3f) | 0xc080 as binary(2))
if @c >= 0x800 and @c < 0x10000
set @d = cast(((@c * 0x10) & 0xFF0000) | ((@c * 4) & 0xFF00) | (@c & 0x3f) | 0xe08080 as binary(3))
if @c >= 0x10000
set @d = cast(((@c * 0x40) & 0xFF000000) | ((@c * 0x10) & 0xFF0000) | ((@c * 4) & 0xFF00) | (@c & 0x3f) | 0xf0808080 as binary(4))
set @r += @d
set @i += 1
return @r

sevaa commented Nov 7, 2016

Unlike the GitHub comment system, it works correctly with characters from Unicode's astral planes.

isken99 commented Oct 24, 2017

Hi Sevaa,
I worked in AP team needs to deal with Asia Characters.
I have tested your SQL function with few Korea and Chinese characters find out the encoding does not meet the internet URL encoding standard.

The left UTF8 is from standard URL encoding, the right one is from the function
〇 E38087 E3C087
ㄱ E384B1 E3C4B1
validated with

There seems to be a pattern of the wrong encoding on the second byte 80 -> C0 and 84 -> C4.

I am not familiar bitwise and hex calculation at all. I really hope to fix it. Will you be quickly discover why?

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