How does shortest path work in pgrouting?

Question

I'm trying to find how the implementation of shortest_path() in pgRouting works.

This is the function definition:

CREATE OR REPLACE FUNCTION shortest_path(sql text, source_id integer,target_id integer, directed boolean, has_reverse_cost boolean)  
RETURNS SETOF path_result AS '$libdir/librouting', 'shortest_path'  
  LANGUAGE c IMMUTABLE STRICT  
  COST 1  
  ROWS 1000;  
ALTER FUNCTION shortest_path(text, integer, integer, boolean, boolean) OWNER TO postgres;

My questions are:

1. How does it calls the .c file and how it passes the parameters to it (I believe it's dijkstra.c file, correct?)
2. How can I take that .c file and compile it with the debug info it has in order to see how it works so I can understand it better?

Answer 1

Here is the source for dijkstra.c. You can read this code to see what the function is doing. The SQL you posted just shows the binding to the native C function.