diff --git a/lib/path-set.js b/lib/path-set.js
new file mode 100644
index 0000000..e7ab8b7
--- /dev/null
+++ b/lib/path-set.js
@@ -0,0 +1,180 @@
+/**
+ * Copyright 2013-2016  Zaid Abdulla
+ *
+ * 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/>.
+ */
+"use strict";
+
+
+class PathSet {
+
+  constructor() {
+    this.lengthIndex = [];
+    this.fragmentIndex = [];
+  }
+
+
+  get depth() {
+    return this.lengthIndex.length;
+  }
+
+
+  add(path) {
+    var sets = [];
+
+    if (!this.lengthIndex[path.length]) {
+      sets = null;
+      this.lengthIndex[path.length] = new Set();
+    }
+    else if (sets) {
+      sets.push(this.lengthIndex[path.length])
+    }
+
+    for (let i = 0; i < path.length; ++ i) {
+      let fragment = path[i];
+
+      if (!fragment)
+        throw new Error('All array elements must be non-empty string');
+
+      if (!this.fragmentIndex[i]) {
+        sets = null;
+        this.fragmentIndex[i] = {}
+      }
+
+      if (!this.fragmentIndex[i][fragment]) {
+        sets = null
+        this.fragmentIndex[i][fragment] = new Set();
+      }
+      else if (sets)
+        sets.push(this.fragmentIndex[i][fragment])
+    }
+
+    if (sets) {
+      sets.sort(function(a, b) {
+        return a.size - b.size;
+      });
+
+      var smallest = sets.shift();
+      for (let p of smallest) {
+        for (let set of sets) {
+          if (!set.has(p)) {
+            p = null;
+            break;
+          }
+        }
+
+        if (p)
+          return p;
+      }
+    }
+
+    var wildcards = 0;
+    this.lengthIndex[path.length].add(path);
+    for (let i = 0; i < path.length; ++ i) {
+      let fragment = path[i];
+      if (fragment === '*')
+        wildcards |= 1 << i;
+
+      this.fragmentIndex[i][fragment].add(path);
+    }
+
+    if (path.wildcards == null) {
+      path.wildcards = wildcards;
+      Object.freeze(path);
+    }
+    return path;
+  }
+
+
+  *subset(path, depth) {
+    var p = path.slice();
+    for (let i = 0; i < p.length; ++ i)
+      if (p[i] === '*')
+        p[i] = null;
+    yield* this.find(p, depth || 0, false);
+  }
+
+
+  *superset(path, depth) {
+    yield* this.find(path, depth || 0, true)
+  }
+
+
+  *find(pattern, depth, wildcard) {
+    var sets = [];
+
+    var s = [];
+    for (let i = pattern.length + depth; i >= pattern.length; -- i) {
+      if (this.lengthIndex[i])
+        s.push(this.lengthIndex[i]);
+    }
+
+    if (!s.length)
+      return;
+
+    sets.push(s);
+
+    for (let i = 0; i < pattern.length; ++ i) {
+      if (pattern[i]) {
+        let fragment = pattern[i];
+        let s = [];
+
+        if (this.fragmentIndex[i]) {
+          if (this.fragmentIndex[i][fragment])
+            s.push(this.fragmentIndex[i][fragment]);
+
+          if (wildcard && this.fragmentIndex[i]['*'])
+            s.push(this.fragmentIndex[i]['*'])
+        }
+
+        if (!s.length)
+          return;
+
+        sets.push(s);
+      }
+    }
+
+    sets.sort(function(a, b) {
+      return a.reduce(function(prev, cur) {return prev + cur.size;}, 0) -
+        b.reduce(function(prev, cur) {return prev + cur.size;}, 0);
+    });
+
+    var smallest = sets.shift();
+    for (let pp of smallest) {
+      for (let p of pp) {
+        for (let ss of sets) {
+          let found = false;
+          for (let s of ss) {
+            if (s.has(p)) {
+              found = true;
+              break;
+            }
+          }
+
+          if (!found) {
+            p = null;
+            break;
+          }
+        }
+
+        if (p)
+          yield p;
+      }
+    }
+  }
+
+}
+
+
+module.exports = PathSet;