[Gdal-dev] VC++ Wrapper

[Frank Warmerdam]

Matthew Hanson wrote:
> Hi, 
> 
> I'm working on a managed wrapper for GDAL to create a .NET assembly. 
> 
> I just wanted to clarify a few things.  The C++ API (in gdal_priv.h) looks
> like it's a C++ wrapper to the underlying C code.  Is this true?  If so, I
> think I'd rather interface with the C API then end up having a wrapper
> around a wrapper.   Are there any benefits to using the C++ API?  

Matt,

The C++ API is actually the "real" implementation.  The C API is just
thin wrappers around it.  Nevertheless, I encourage you to target the C API
because it is much less "fragile" than the C++ API.  It becomes almost
impossible to substitute new versions of GDAL DLLs into an application that
calls the C++ API directly because of minor changes in method signatures
(like const correctness changes) or any change in the internal layout of
C++ objects (add new data members for instance).

So my experience has been that wrappers and applications written against
the C API are less tightly linked to a specific version of GDAL than C++
API callers.

> Also, there looks like there's some parts of GDAL (like the warp API) that
> are only in C++.  In this case I'd have to use the C++ API.  Are there any
> other parts of GDAL that only have a C++ API?

Alternatively, you can point out these issues to me, and I can look into
preparing C wrappers.  My intent with the warp api would be that a C API should
exist for applications that want to instantiate and invoke a GDALWarpOperation
from an input GDALWarpOptions.  The GDALWarpOptions is deliberately kept as a
simple C structure so it can be created and manipulated smoothly in C.
However, it has alot of callback functions which might be tricky to implement
in a .NET binding.  I have not tried to implement the full warp API in Python
for instance.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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