[gdal-dev] [PROJ] RFC 102: Embedding resource files into libgdal (and PROJ)

[Even Rouault]

Hi,

Proposed implementations are, as far as I can tell, feature complete now 
(including docs & CI):

- GDAL: https://github.com/OSGeo/gdal/pull/10972 . I propose that we 
target 3.11. We are probably too close to the feature freeze of 3.10 and 
would otherwise need to rush things, which feels unnecessary.

- PROJ: https://github.com/OSGeo/PROJ/pull/4265 . Embedding has also 
been extended to proj.ini , in addition to proj.db (both available in 
non-C23 or C23 modes)

I've also updated the RFC text to reflect the current state of things.

I let more time for people to review before submitting to vote, probably 
end of next week (as usual, tell if you need more time)

Even

Le 03/10/2024 à 19:30, Even Rouault via PROJ a écrit :
> Hi,
>
> I've now a PROJ branch with proj.db embedding working at 
> https://github.com/OSGeo/PROJ/pull/4265. And contrary to the current 
> wording of the RFC text, I've actually invested in making it work with 
> non-C23 compilers too (C23 mechanism used when available), by adapting 
> https://gitlab.com/jhamberg/cmake-examples/-/blob/master/cmake/FileEmbed.cmake 
> and optimizing it because its performance at generating a .c file from 
> a binary was not acceptable on multi-megabyte large files like 
> proj.db.  Non-C23 embedding works fine with older gcc, clang, MSVC. 
> The proj_db.c generation from proj.db runs in 8 seconds, and building 
> it with gcc in 18 seconds (looking at build times in CI, that seems to 
> be fast with MSVC too)
>
> But I won't (probably) support non-C23 embedding for GDAL: that would 
> be too much complication w.r.t benefit. Only a "few" GDAL drivers need 
> resource files, whereas access to proj.db is a strong requirement.
>
> Kurt, I had to modify the memOpen() and the memvfs_init() functions of 
> the https://www.sqlite.org/src/doc/tip/ext/misc/memvfs.c (I did other 
> changes in memvfs_init() to avoid making it the default VFS, and 
> registering it per db-connection to avoid a global registration), 
> otherwise some complex SQL requests that require creating a temporary 
> file wouldn't work, such as the ones of 'bin/projinfo --list-crs' or 
> 'bin/cct "this is a bogus CRS meant to trigger a syntax error in 
> proj_create"'  (with sqlite 3.46 of fedora:rawhide). Is it something 
> you ran into? Cf the changes in memvfs.c in 
> https://github.com/rouault/PROJ/commit/e7fcf162f6968c48587836f537b506708112e7d4
>
> With those changes, ctest pass
>
> Even
>
>
> http://www.spatialys.com
> My software is free, but my time generally not.
>
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