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-rw-r--r--src/vppinfra/ptclosure.c125
1 files changed, 125 insertions, 0 deletions
diff --git a/src/vppinfra/ptclosure.c b/src/vppinfra/ptclosure.c
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+/*
+ * 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:
+ */