[geos-devel] RFC for Thread safe CAPI announced

[Frank Warmerdam]

Chuck Thibert wrote:
> RFC updated.
> 

Chuck,

I notice that the application still needs to pass a pointer to a
GEOSContextHandle_t structure into initGEOS_r() instead of having
initGEOS_r() allocate the structure internally.  Was there a reason for
this?  As I mentioned before, I think this makes the interface brittle
in the sense that the application code has to be recompiled any time
the contents of the context structure change.  My suggested alternative
is:

   GEOSContextHandle_t initGEOS_r( GEOSMessageHandler notice_function,
                                   GEOSMessageHandler error_function);

I'd add that I'd like the RFC to define the context of the context
structure.  I also think that the application visible handle should be
declared:

   type void *GEOSContextHandle_t;

so that it would be passed around as a value rather than a pointer.  This
isn't really very important, but I think it makes the opaqueness of the
handle clearer.  This is the same model used by all the handles for objects
in the GDAL and OGR C APIs for instance.

Last, I *think* that the _r appended to some C library functions implies
reentrancy, while I think this RFC aimed only at thread-safety.  If that
is the case the original idea of appending _TS might be better than _r to
avoid fooling people into thinking the C API is reentrant (that is that
multiple threads could operate on the same context at the same time).

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent