diff --git a/src/locked_queue.hh b/src/locked_queue.hh
deleted file mode 100644
index 008ecdd..0000000
--- a/src/locked_queue.hh
+++ /dev/null
@@ -1,180 +0,0 @@
-// This file is under GNU General Public License 3.0
-// see LICENSE.txt
-
-#ifndef LIBPEPADAPTER_LOCKED_QUEUE_HH
-#define LIBPEPADAPTER_LOCKED_QUEUE_HH
-
-#include <deque>
-#include <condition_variable>
-#include <mutex>
-
-namespace utility {
-    template<class T, void (*Deleter)(T) = nullptr>
-    class locked_queue {
-        typedef std::recursive_mutex Mutex;
-        typedef std::unique_lock<Mutex> Lock;
-
-        int _waiting = 0;
-        Mutex _mtx;
-        std::condition_variable_any _cv;
-        std::deque<T> _q;
-
-    public:
-        ~locked_queue()
-        {
-            clear();
-        }
-
-        void clear()
-        {
-            Lock L(_mtx);
-            if (Deleter != nullptr) {
-                for (auto q : _q) {
-                    Deleter(q);
-                }
-            }
-            _q.clear();
-        }
-
-        // defined behavior when queue empty
-        T back()
-        {
-            Lock lg(_mtx);
-            if (_q.empty())
-                throw std::underflow_error("queue empty");
-            return _q.back();
-        }
-
-        // defined behavior when queue empty
-        T front()
-        {
-            Lock lg(_mtx);
-            if (_q.empty())
-                throw std::underflow_error("queue empty");
-            return _q.front();
-        }
-
-        // returns a copy of the last element.
-        // blocks when queue is empty
-        T pop_back()
-        {
-            Lock L(_mtx);
-            _cv.wait(L, [&] { return !_q.empty(); });
-            T r{std::move(_q.back())};
-            _q.pop_back();
-            return r;
-        }
-
-        // returns a copy of the first element.
-        // blocks when queue is empty
-        T pop_front()
-        {
-            Lock L(_mtx);
-            _cv.wait(L, [&] { return !_q.empty(); });
-            T r{std::move(_q.front())};
-            _q.pop_front();
-            return r;
-        }
-
-        // returns true and set a copy of the last element and pop it from queue if there is any
-        // returns false and leaves 'out' untouched if queue is empty even after 'end_time'
-        bool try_pop_back(T& out, std::chrono::steady_clock::time_point end_time)
-        {
-            Lock L(_mtx);
-            ++_waiting;
-            if (!_cv.wait_until(L, end_time, [this] { return !_q.empty(); })) {
-                --_waiting;
-                return false;
-            }
-
-            --_waiting;
-            out = std::move(_q.back());
-            _q.pop_back();
-            return true;
-        }
-
-        // returns true and set a copy of the first element and pop it from queue if there is any
-        // returns false and leaves 'out' untouched if queue is empty even after 'end_time'
-        bool try_pop_front(T& out, std::chrono::steady_clock::time_point end_time)
-        {
-            Lock L(_mtx);
-            ++_waiting;
-            if (!_cv.wait_until(L, end_time, [this] { return !_q.empty(); })) {
-                --_waiting;
-                return false;
-            }
-
-            --_waiting;
-            out = std::move(_q.front());
-            _q.pop_front();
-            return true;
-        }
-
-        // returns true and set a copy of the first element and pop it from queue if there is any
-        // returns false and leaves 'out' untouched if queue is empty even after 'duration'
-        bool try_pop_front(T& out, std::chrono::seconds duration)
-        {
-            Lock L(_mtx);
-            ++_waiting;
-            if (!_cv.wait_for(L, duration, [this] { return !_q.empty(); })) {
-                --_waiting;
-                return false;
-            }
-
-            --_waiting;
-            out = std::move(_q.front());
-            _q.pop_front();
-            return true;
-        }
-
-
-        void push_back(const T& data)
-        {
-            {
-                Lock L(_mtx);
-                _q.push_back(data);
-            }
-            _cv.notify_one();
-        }
-
-        void emplace_back(const T& data)
-        {
-            {
-                Lock L(_mtx);
-                _q.emplace_back(data);
-            }
-            _cv.notify_one();
-        }
-
-        void push_front(const T& data)
-        {
-            {
-                Lock L(_mtx);
-                _q.push_front(data);
-            }
-            _cv.notify_one();
-        }
-
-        size_t size()
-        {
-            Lock lg(_mtx);
-            return _q.size();
-        }
-
-        bool empty()
-        {
-            Lock lg(_mtx);
-            return _q.empty();
-        }
-
-        // returns the number of threads that are waiting in pop_...() or try_pop_...()
-        int waiting()
-        {
-            Lock L(_mtx);
-            return _waiting;
-        }
-    };
-
-} // end of namespace utility
-
-#endif // LIBPEPADAPTER_LOCKED_QUEUE_HH