FW: Win32 unicode vs ICU

I just realised this mail didn't go through. Probably because it was too
large for -hackers. So: repost to -patches. Sorry about that. If it's a
duplicate, even more sorry, but I couldn't find it in the archives.

(This may explain that nobody answered me :P)

//Magnus

> -----Original Message-----
> From: Magnus Hagander
> Sent: Sunday, July 31, 2005 2:09 PM
> To: PostgreSQL-development
> Cc: pgsql-hackers-win32(at)postgresql(dot)org
> Subject: Win32 unicode vs ICU
>
> Hi!
>
> I've been working with Palles ICU patch to make it work on
> win32, and I believe I have it done. While doing it I noticed
> that ICU basically converts to UTF16 and back - I previously
> thought it worked on UTF8 strings. Based on this I also tried
> out an implementation for the win32-unicode problem that does
> *not* require ICU. It uses the win32 native functions to map
> to utf16 and back, and then to process the text there. And I
> got through with much less code than the ICU version, while
> doing the same thing.
>
> I am unsure of how to proceed. As I see it there are three paths:
> 1) Use native win32 functionality only on win32
> 2) Use ICU functionality only on win32
> 3) Allow both ICU and native functionality, compile time
> switch --with-icu (same as unix with the ICU patch)
>
>
> The main downsides of ICU vs the native ones are:
> * ICU does not accept win32 locale names. When doing
> setlocale("sv_se"), for example, win32 will return this in
> later calls as "Swedish_Sweden.1252". To get around this in
> the ICU patch, I had to implement a lookup map that converts
> it back to sv_se for ICU.
>
> * ICU is yet another build and runtime dependency, and a
> large one (comes in at 11Mb for the DLL files alone in the
> win32 download)
>
>
> I guess that the main upside of it is that we'd get
> constistent behaviour - in case there are issues with either
> ICU or win32 native they'd otherwise differ. And only one new
> codepath. But we already live with the platform-inconsistency today...
>
> Another upside is that it handles more encodings in ICU - my
> native implementation does *only* UTF8 and relies on existing
> functionality to deal with other encodings. It could of
> course be extended if necessary, but from what I can tell
> UTF8 is the big one.
>
>
>
> I have attached both patches. For the native version, only
> win32_utf8.patch is required. For the ICU version,
> icu_win32.patch is needed and also the files
> localemap.c,localemap.pl, iso639 and iso3166 needs to go in
> src/backend/port/win32. (the localemap needs to be updated to
> do a better-than-linear search, but I wanted to include an example)
>
>
> Thoughts on the options?
>
>
> And anohter question - my native patch touches the same
> functions as the ICU patch. Can somebody who knows the
> internals confirm or deny that these are all the required
> locations, or do we need to modify more?
>
> (I have run simple tests in swedish locale and both behave
> the same and correct, but I'm unsure of exactly how much
> would be affected)
>
> Finally, the win32 patch also changes the normal path to use
> strncoll(). The comment above the function states that we'd
> like to use strncoll but it's not available. Well, on win32
> it is, so it should provide a speedup on win32. It is
> currently not included in the ICU patch, but should probably
> be included whichever path we'd chose.
>
>
> //Magnus
>