1 files changed, 125 insertions, 0 deletions
diff --git a/src/vppinfra/ptclosure.c b/src/vppinfra/ptclosure.c
new file mode 100644
index 00000000000..cda873ef442
--- /dev/null
+++ b/src/vppinfra/ptclosure.c
@@ -0,0 +1,125 @@
+/*
+ * Copyright (c) 2016 Cisco and/or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <vppinfra/ptclosure.h>
+
+u8 **
+clib_ptclosure_alloc (int n)
+{
+  u8 **rv = 0;
+  u8 *row;
+  int i;
+
+  ASSERT (n > 0);
+
+  vec_validate (rv, n - 1);
+  for (i = 0; i < n; i++)
+    {
+      row = 0;
+      vec_validate (row, n - 1);
+
+      rv[i] = row;
+    }
+  return rv;
+}
+
+void
+clib_ptclosure_free (u8 ** ptc)
+{
+  u8 *row;
+  int n = vec_len (ptc);
+  int i;
+
+  ASSERT (n > 0);
+
+  for (i = 0; i < n; i++)
+    {
+      row = ptc[i];
+      vec_free (row);
+    }
+  vec_free (ptc);
+}
+
+void
+clib_ptclosure_copy (u8 ** dst, u8 ** src)
+{
+  int i, n;
+  u8 *src_row, *dst_row;
+
+  n = vec_len (dst);
+
+  for (i = 0; i < vec_len (dst); i++)
+    {
+      src_row = src[i];
+      dst_row = dst[i];
+      clib_memcpy (dst_row, src_row, n);
+    }
+}
+
+/*
+ * compute the positive transitive closure
+ * of a relation via Warshall's algorithm.
+ *
+ * Ref:
+ * Warshall, Stephen (January 1962). "A theorem on Boolean matrices".
+ * Journal of the ACM 9 (1): 11–12.
+ *
+ * foo[i][j] = 1 means that item i
+ * "bears the relation" to item j.
+ *
+ * For example: "item i must be before item j"
+ *
+ * You could use a bitmap, but since the algorithm is
+ * O(n**3) in the first place, large N is inadvisable...
+ *
+ */
+
+u8 **
+clib_ptclosure (u8 ** orig)
+{
+  int i, j, k;
+  int n;
+  u8 **prev, **cur;
+
+  n = vec_len (orig);
+  prev = clib_ptclosure_alloc (n);
+  cur = clib_ptclosure_alloc (n);
+
+  clib_ptclosure_copy (prev, orig);
+
+  for (k = 0; k < n; k++)
+    {
+      for (i = 0; i < n; i++)
+	{
+	  for (j = 0; j < n; j++)
+	    {
+	      cur[i][j] = prev[i][j] || (prev[i][k] && prev[k][j]);
+	    }
+	}
+      clib_ptclosure_copy (prev, cur);
+    }
+  clib_ptclosure_free (prev);
+  return cur;
+}
+
+
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */