Add domain-specific language for BPF policies

sandbox/linux/seccomp-bpf-helpers/cons.h

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SANDBOX_LINUX_SECCOMP_BPF_HELPERS_CONST_LIST_H_
+#define SANDBOX_LINUX_SECCOMP_BPF_HELPERS_CONST_LIST_H_
+
+#include "base/memory/ref_counted.h"
+#include "sandbox/sandbox_export.h"
+
+namespace sandbox {
+
+// Cons provides an immutable linked list abstraction as commonly
+// provided in functional programming languages like Lisp or Haskell.
+template <typename T>
+class Cons : public base::RefCounted<Cons<T> > {
+ public:
+  // List provides an abstraction for referencing a list of zero or
+  // more Cons nodes.
+  typedef scoped_refptr<const Cons<T> > List;
+
+  // Return this node's head element.
+  const T& head() const { return head_; }
+
+  // Return this node's tail element.
+  List tail() const { return tail_; }
+
+  // Construct a new List using |head| and |tail|.
+  static List Make(const T& head, List tail) {
+    return make_scoped_refptr(new const Cons<T>(head, tail));
+  }
+
+ private:
+  Cons(const T& head, List tail) : head_(head), tail_(tail) {}
+  virtual ~Cons() {}
+
+  T head_;
+  List tail_;
+
+  friend class base::RefCounted<Cons<T> >;
+  DISALLOW_COPY_AND_ASSIGN(Cons);
+};
+
+}  // namespace sandbox
+
+#endif  // SANDBOX_LINUX_SECCOMP_BPF_HELPERS_CONST_LIST_H_