aga,agar: Add edge costs

This allows the edge_info callback to supply a cost or length for an edge.
For now we only support 'long' valued costs.  If the callback doesn't
supply a cost, it's considered cost 1.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

ccan/aga/aga.c

@@ -93,6 +93,7 @@ int aga_edge_info(const struct aga_graph *g, const struct aga_node *n,
 	int rc;
 
 	ei->to = NULL;
+	ei->icost = 1;
 	rc = g->edge_info(g, n, e, ei);
 	assert(rc <= 0);
 	return rc;

ccan/aga/aga.h

@@ -72,6 +72,10 @@
  *   reference to that node by the edge callback for *any* node and
  *   index MUST use the same pointer.
  *
+ * - The ei->icost field MAY be set by the edge_info callback to
+ *   indicate the edge's cost / length represented as an integer (of
+ *   type aga_icost_t),  Otherwise the cost defaults to 1.
+ *
  * Concurrency
  * ===========
  *
@@ -127,9 +131,13 @@ typedef const void *(*aga_next_edge_fn)(const struct aga_graph *g,
 					const struct aga_node *n,
 					const void *e);
 
+typedef long aga_icost_t;
+
 struct aga_edge_info {
 	struct aga_node *to;
+	aga_icost_t icost; /* integer edge cost */
 };
+
 typedef int (*aga_edge_info_fn)(const struct aga_graph *g,
 				const struct aga_node *n,
 				const void *e, struct aga_edge_info *ei);

ccan/agar/agar.c

@@ -79,6 +79,7 @@ static int convert_edge_info(const struct aga_graph *g,
 	int rc;
 
 	eir.to = NULL;
+	eir.icost = ei->icost; /* Inherit the default from aga */
 
 	rc = sr->gr->edge_info(sr->gr, nr, e, &eir);
 
@@ -87,6 +88,8 @@ static int convert_edge_info(const struct aga_graph *g,
 	else
 		ei->to = NULL;
 
+	ei->icost = eir.icost;
+
 	return rc;
 }
 
@@ -164,6 +167,7 @@ int agar_edge_info(const struct agar_graph *gr, const void *nr, const void *e,
 	int rc;
 
 	eir->to = NULL;
+	eir->icost = 1;
 	rc = gr->edge_info(gr, nr, e, eir);
 	assert(rc <= 0);
 	return rc;

ccan/agar/agar.h

@@ -9,6 +9,7 @@
 
 struct agar_edge_info {
 	const void *to;
+	aga_icost_t icost; /* integer edge cost */
 };
 
 struct agar_graph;