c function: keep objects in memory for all session or all transaction

Hi everybody,  I am new PostgreSQL c function programmer.  I'm trying to move ahead 
a new "PostgreSQL routing library" (http://www.pgroute.org [for now, the 
page in only in spanish]).

The point:
There is some way to keep objects in [persisten] memory and then refer 
to these from c functions?.  In the current version of pgRoute, each 
transaction load the graph in memory (using MemoryContext), this isn't a 
enterprise solution for routing program.  Why I Wish is using a c 
function to load the graph in memory [persistent], something like:

SELECT pgr_load_graph('my SQL graph sentence', 'graph name');    example: SELECT pgr_load_graph('SELECT id, source,
target,
 
cost1,cost2,costn,... FROM edge_table WHERE ...','My graph');
would also have a function to unload or delete.

and then, use other function to calculating the shortest path, something 
like:
SELECT pgr_get_shortest_path('from','to','cost 
column','algorithm','graph name');    example: SELECT 
pgr_get_shortest_path(6000,5142,'cost1','dijkstra','My graph');


researching in the PostgreSQL source code I found 
"postgresql-8.4.0/src/backend/utils/mmgr/README.TXT", and I think the 
indicated MemoryContext that I need to solved my problem is 
"TopMemoryContext", but I don't found examples of how can I used it.

I need some guidelines, or way to resolved this.  Is posible to put 
persisten object in memory through postgresql c funtion?, or my idea is 
a crazy idea?

Thanks a lot for your time and answers,  ahhh! and for my English writing.