TypeScript!

lib/gpn-heuristic.ts

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+/**
+ * Copyright 2013-2018  Zaid Abdulla
+ *
+ * This file is part of GenieACS.
+ *
+ * GenieACS is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * GenieACS is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with GenieACS.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+const WILDCARD_MULTIPLIER = 2;
+const UNDISCOVERED_DEPTH = 7;
+
+// Simple heuristic to estimate GPN count given a set of patterns to be
+// discovered. Used to decide whether to use nextLevel = false in GPN.
+// gpnPatterns is [pattern, flags]
+// pattern is a path (array)
+// flags is an int where its bits mark the segments in the pattern that
+// need refreshing. Leading 0s indicate that the pattern up to that
+// point has been discovered.
+export function estimateGpnCount(gpnPatterns, depth = 0): number {
+  const children = {};
+  const wildcardChildren = [];
+  let wildcardDiscovered = false;
+  let gpnCount = 0;
+
+  for (const pattern of gpnPatterns) {
+    const path = pattern[0];
+    const flags = pattern[1] >> depth;
+
+    const k = path[depth];
+
+    if (!k) {
+      if (flags & 1) gpnCount = 1;
+      continue;
+    }
+
+    if (flags & 1) {
+      gpnCount = 1;
+
+      if (depth > UNDISCOVERED_DEPTH) continue;
+    } else if (k === "*") {
+      wildcardDiscovered = true;
+    }
+
+    if (k === "*") {
+      wildcardChildren.push(pattern);
+    } else {
+      children[k] = children[k] || [];
+      children[k].push(pattern);
+    }
+  }
+
+  let wildcardGpnCount = 0;
+  if (!wildcardDiscovered && wildcardChildren.length) {
+    wildcardGpnCount +=
+      estimateGpnCount(wildcardChildren, depth + 1) * WILDCARD_MULTIPLIER;
+  }
+
+  for (const k of Object.keys(children)) {
+    const c = estimateGpnCount(children[k].concat(wildcardChildren), depth + 1);
+    wildcardGpnCount -= c;
+    gpnCount += c;
+  }
+
+  gpnCount += Math.max(0, wildcardGpnCount);
+
+  return gpnCount;
+}