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+/*
+ * This file is part of PowerDNS or dnsdist.
+ * Copyright -- PowerDNS.COM B.V. and its contributors
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * In addition, for the avoidance of any doubt, permission is granted to
+ * link this program with OpenSSL and to (re)distribute the binaries
+ * produced as the result of such linking.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+#pragma once
+#include <map>
+#include <time.h>
+#include <thread>
+
+/**
+   General idea: many threads submit work to this class, but only one executes it. The work should therefore be entirely trivial.
+   The implementation is that submitter threads create an object that represents the work, and it gets sent over a pipe 
+   to the worker thread.
+
+   The worker thread meanwhile listens on this pipe (non-blocking), with a delay set to the next object that needs to be executed.
+   If meanwhile new work comes in, all objects who's time has come are executed, a new sleep time is calculated.
+*/
+
+
+/* ObjectPipe facilitates the type-safe passing of types over a pipe */
+
+template<class T>
+class ObjectPipe
+{
+public:
+  ObjectPipe();
+  ~ObjectPipe();
+  void write(T& t);
+  int readTimeout(T* t, double msec); //!< -1 is timeout, 0 is no data, 1 is data. msec<0 waits infinitely long. msec==0 = undefined
+  void close(); 
+private:
+  int d_fds[2];
+};
+
+template<class T>
+class DelayPipe
+{
+public:
+  DelayPipe();
+  ~DelayPipe();
+  void submit(T& t, int msec); //!< don't try for more than 4294 msec
+
+private:
+  void worker();
+  struct Combo
+  {
+    T what;
+    struct timespec when;
+  };
+
+  double tsdelta(const struct timespec& a, const struct timespec& b) // read as a-b
+  {
+    return 1.0*(a.tv_sec-b.tv_sec)+1.0*(a.tv_nsec-b.tv_nsec)/1000000000.0;
+  }
+
+  ObjectPipe<Combo> d_pipe;
+  struct tscomp {
+    bool operator()(const struct timespec& a, const struct timespec& b) const
+    {
+      return std::tie(a.tv_sec, a.tv_nsec) < std::tie(b.tv_sec, b.tv_nsec);
+    }
+  };
+  std::multimap<struct timespec, T, tscomp> d_work;
+  void gettime(struct timespec* ts);
+  std::thread d_thread;
+};
+
+#include "delaypipe.cc"