1 files changed, 63 insertions, 0 deletions
diff --git a/nest/a-path.c b/nest/a-path.c
index 712e77a3..b1812981 100644
--- a/nest/a-path.c
+++ b/nest/a-path.c
@@ -287,6 +287,69 @@ as_path_match_set(struct adata *path, struct f_tree *set)
   return 0;
 }
 
+struct adata *
+as_path_filter(struct linpool *pool, struct adata *path, struct f_tree *set, u32 key, int pos)
+{
+  if (!path)
+    return NULL;
+
+  int len = path->length;
+  u8 *p = path->data;
+  u8 *q = path->data + len;
+  u8 *d, *d2;
+  int i, bt, sn, dn;
+  u8 buf[len];
+
+  d = buf;
+  while (p<q)
+    {
+      /* Read block header (type and length) */
+      bt = p[0];
+      sn = p[1];
+      dn = 0;
+      p += 2;
+      d2 = d + 2;
+
+      for (i = 0; i < sn; i++)
+	{
+	  u32 as = get_as(p);
+	  int match;
+
+	  if (set)
+	    match = !!find_tree(set, (struct f_val){T_INT, .val.i = as});
+	  else
+	    match = (as == key);
+
+	  if (match == pos)
+	    {
+	      put_as(d2, as);
+	      d2 += BS;
+	      dn++;
+	    }
+
+	  p += BS;
+	}
+
+      if (dn > 0)
+	{
+	  /* Nonempty block, set block header and advance */
+	  d[0] = bt;
+	  d[1] = dn;
+	  d = d2;
+	}
+  }
+
+  int nl = d - buf;
+  if (nl == path->length)
+    return path;
+
+  struct adata *res = lp_alloc(pool, sizeof(struct adata) + nl);
+  res->length = nl;
+  memcpy(res->data, buf, nl);
+
+  return res;
+}
+
 
 struct pm_pos
 {