stream/iterator map context nodes (Re: [redland-dev] [patch] librdf_storage_hashes_context_serialise_get_statement)

[John Fieber]

On May 7, 2008, at 1:38 AM, Dave Beckett wrote:

> Lauri Aalto wrote:
>> [adding APIs for stream/iterator map callbacks that supply context  
>> nodes]
>
> Seems fine to me, but do you have a use for this?  If the answer is
> yes then I'd be more confident that this is the right API.

I have an application that depends (critically) on being able to  
examine the context nodes in an iterator/stream.  I could, of course,  
create my own iterator wrapper, but the map function is much simpler  
(== less code == less opportunity for bugs), but I need access to the  
context node in the map function.

While adding additional map_handler forms would address the problem, I  
think it would be cleaner to add a map_handler-safe version of  
librdf_[iterator|stream]_get_context, or work out a way to make the  
existing function map_handler safe, i.e. not result in a recursive  
call to librdf_[iterator|stream]_update_current_element().  It might  
do to change boolean "is_updated" into three states to include  
"is_mapping" to break the infinite recursion in librdf_[iterator| 
stream]_update_current_element() when processing mapping functions.

If I get a few spare cycles I'll investigate this.

-john