lib: move check_bit into prefix common code

Make one version of check prefix bit, and put it inline
with proper prototype. This gets rid of some macro's and also some
assert() that can never happen on a non-broken compiler.

* bgpd/bgp_table.c
  * CHECK_BIT(): sayonara
  * check_bit(): sayonara
  * SET_LINK(): sayonara
  * set_link(): make use of prefix_bit() instead of check_bit()
  * bgp_node_match(): idem
  * bgp_node_lookup(): idem
  * bgp_node_get(): idem
* lib/prefix.h
  * prefix_bit(): new inline version of check_bit()
* lib/table.c
  * CHECK_BIT(): sayonara
  * check_bit(): sayonara
  * SET_LINK(): sayonara
  * set_link(): make use of prefix_bit() instead of check_bit()
  * route_node_match(): idem
  * route_node_lookup(): idem
  * route_node_get(): idem
* ospf6d/ospf6_lsdb.c
  * CHECK_BIT(): sayonara
  * ospf6_lsdb_lookup_next(): make use of prefix_bit() instead of
    CHECK_BIT()
  * ospf6_lsdb_type_router_head(): idem
  * ospf6_lsdb_type_head(): idem
* ospf6d/ospf6_route.c
  * CHECK_BIT(): sayonara
  * ospf6_route_match_head() make use of prefix_bit() instead of
  * CHECK_BIT()
diff --git a/lib/prefix.h b/lib/prefix.h
index 9cfc155..d370720 100644
--- a/lib/prefix.h
+++ b/lib/prefix.h
@@ -127,6 +127,16 @@
 /* Prefix's family member. */
 #define PREFIX_FAMILY(p)  ((p)->family)
 
+/* Check bit of the prefix. */
+static inline unsigned int
+prefix_bit (const u_char *prefix, const u_char prefixlen)
+{
+  unsigned int offset = prefixlen / 8;
+  unsigned int shift  = 7 - (prefixlen % 8);
+
+  return (prefix[offset] >> shift) & 1;
+}
+
 /* Prototypes. */
 extern int afi2family (int);
 extern int family2afi (int);
diff --git a/lib/table.c b/lib/table.c
index 06c6453..04df3af 100644
--- a/lib/table.c
+++ b/lib/table.c
@@ -165,37 +165,10 @@
     }
 }
 
-/* Macro version of check_bit (). */
-#define CHECK_BIT(X,P) ((((u_char *)(X))[(P) / 8]) >> (7 - ((P) % 8)) & 1)
-
-/* Check bit of the prefix. */
-static int
-check_bit (const u_char *prefix, u_char prefixlen)
-{
-  unsigned int offset;
-  unsigned int shift;
-  const u_char *p = prefix;
-
-  assert (prefixlen <= 128);
-
-  offset = prefixlen / 8;
-  shift = 7 - (prefixlen % 8);
-  
-  return (p[offset] >> shift & 1);
-}
-
-/* Macro version of set_link (). */
-#define SET_LINK(X,Y) do { (X)->link[CHECK_BIT(&(Y)->p.u.prefix,(X)->p.prefixlen)] = (Y);\
-                      (Y)->parent = (X); } while (0)
-
 static void
 set_link (struct route_node *node, struct route_node *new)
 {
-  int bit;
-    
-  bit = check_bit (&new->p.u.prefix, node->p.prefixlen);
-
-  assert (bit == 0 || bit == 1);
+  unsigned int bit = prefix_bit (&new->p.u.prefix, node->p.prefixlen);
 
   node->link[bit] = new;
   new->parent = node;
@@ -236,7 +209,7 @@
     {
       if (node->info)
 	matched = node;
-      node = node->link[check_bit(&p->u.prefix, node->p.prefixlen)];
+      node = node->link[prefix_bit(&p->u.prefix, node->p.prefixlen)];
     }
 
   /* If matched route found, return it. */
@@ -290,7 +263,7 @@
       if (node->p.prefixlen == p->prefixlen && node->info)
 	return route_lock_node (node);
 
-      node = node->link[check_bit(&p->u.prefix, node->p.prefixlen)];
+      node = node->link[prefix_bit(&p->u.prefix, node->p.prefixlen)];
     }
 
   return NULL;
@@ -315,7 +288,7 @@
 	  return node;
 	}
       match = node;
-      node = node->link[check_bit(&p->u.prefix, node->p.prefixlen)];
+      node = node->link[prefix_bit(&p->u.prefix, node->p.prefixlen)];
     }
 
   if (node == NULL)