From 16427a5c892ba061a2521f16b76fd6c96c9411ad Mon Sep 17 00:00:00 2001
From: bergmann <info@bergmann89.de>
Date: Fri, 22 Nov 2019 22:26:41 +0100
Subject: [PATCH] * Implemented 'interval' stream * Implemented 'for_each'
 stream method * More refactoring and unit tests

---
 include/asyncpp/core.h                        |  1 -
 include/asyncpp/core/future.h                 | 11 +++
 include/asyncpp/core/future.inl               | 28 ++++++
 include/asyncpp/core/future.pre.h             | 16 ++--
 include/asyncpp/core/future/and_then.h        | 38 ++++++--
 include/asyncpp/core/future/and_then.inl      | 75 +++++++--------
 include/asyncpp/core/future/map.h             | 23 +++++
 include/asyncpp/core/future/map.inl           | 50 +++++-----
 include/asyncpp/core/misc.h                   |  8 ++
 include/asyncpp/core/misc.inl                 | 24 +++++
 include/asyncpp/core/stream.h                 | 20 ++++
 include/asyncpp/core/stream.inl               | 55 +++++++++++
 include/asyncpp/core/stream.pre.h             | 11 ++-
 include/asyncpp/core/stream/for_each.h        | 56 ++++++++++++
 include/asyncpp/core/stream/for_each.inl      | 52 +++++++++++
 include/asyncpp/core/task.h                   | 91 ++-----------------
 include/asyncpp/core/task/current_task_lock.h | 23 +++++
 .../asyncpp/core/task/current_task_lock.inl   | 16 ++++
 .../asyncpp/core/task/current_task_lock.pre.h |  8 ++
 include/asyncpp/core/task/task.h              | 76 ++++++++++++++++
 include/asyncpp/core/task/task.inl            | 37 ++++++++
 include/asyncpp/core/task/task.pre.h          | 13 +++
 include/asyncpp/core/task/task_tpl.h          | 32 +++++++
 .../core/{task.inl => task/task_tpl.inl}      | 24 +----
 include/asyncpp/executor/current_thread.inl   | 24 +----
 include/asyncpp/executor/executor.h           |  8 +-
 include/asyncpp/executor/executor.inl         |  5 +-
 include/asyncpp/timer.h                       |  2 +
 include/asyncpp/timer/delay.h                 | 32 +++++--
 include/asyncpp/timer/delay.inl               | 46 ++++------
 include/asyncpp/timer/impl/registration.h     | 29 +++---
 include/asyncpp/timer/impl/registration.inl   | 17 ++--
 include/asyncpp/timer/impl/registration.pre.h |  9 --
 include/asyncpp/timer/impl/timer_base.h       | 22 +++--
 include/asyncpp/timer/impl/timer_base.inl     | 52 +++++------
 include/asyncpp/timer/interval.h              | 67 ++++++++++++++
 include/asyncpp/timer/interval.inl            | 60 ++++++++++++
 include/asyncpp/timer/timer.h                 |  8 +-
 include/asyncpp/timer/timer.inl               | 45 +++++----
 test/asyncpp/core/future_tests.cpp            |  6 +-
 test/asyncpp/core/stream_tests.cpp            | 28 ++++--
 test/asyncpp/core/task_tests.cpp              |  6 +-
 .../asyncpp/executor/current_thread_tests.cpp |  4 +-
 test/asyncpp/timer/interval_tests.cpp         | 72 +++++++++++++++
 test/helper/runtime_mock.h                    |  2 +-
 45 files changed, 956 insertions(+), 376 deletions(-)
 create mode 100644 include/asyncpp/core/stream/for_each.h
 create mode 100644 include/asyncpp/core/stream/for_each.inl
 create mode 100644 include/asyncpp/core/task/current_task_lock.h
 create mode 100644 include/asyncpp/core/task/current_task_lock.inl
 create mode 100644 include/asyncpp/core/task/current_task_lock.pre.h
 create mode 100644 include/asyncpp/core/task/task.h
 create mode 100644 include/asyncpp/core/task/task.inl
 create mode 100644 include/asyncpp/core/task/task.pre.h
 create mode 100644 include/asyncpp/core/task/task_tpl.h
 rename include/asyncpp/core/{task.inl => task/task_tpl.inl} (59%)
 delete mode 100644 include/asyncpp/timer/impl/registration.pre.h
 create mode 100644 include/asyncpp/timer/interval.h
 create mode 100644 include/asyncpp/timer/interval.inl
 create mode 100644 test/asyncpp/timer/interval_tests.cpp

diff --git a/include/asyncpp/core.h b/include/asyncpp/core.h
index 9869530..78aa6ce 100644
--- a/include/asyncpp/core.h
+++ b/include/asyncpp/core.h
@@ -8,4 +8,3 @@
 #include "core/future.inl"
 #include "core/result.inl"
 #include "core/stream.inl"
-#include "core/task.inl"
diff --git a/include/asyncpp/core/future.h b/include/asyncpp/core/future.h
index 16c5a0f..32465ce 100644
--- a/include/asyncpp/core/future.h
+++ b/include/asyncpp/core/future.h
@@ -4,6 +4,7 @@
 
 #include "result.h"
 #include "future.pre.h"
+
 #include "future/map.h"
 #include "future/and_then.h"
 
@@ -20,6 +21,10 @@ namespace asyncpp
         using trait_type        = future_trait<clean_object_type>;
         using value_type        = typename trait_type::value_type;
         using result_type       = future_result<value_type>;
+        using reference         = clean_object_type&;
+        using pointer           = clean_object_type*;
+        using const_reference   = const clean_object_type&;
+        using const_pointer     = const clean_object_type*;
 
         object_type ref;
 
@@ -46,6 +51,12 @@ namespace asyncpp
          */
         template<typename X_lambda>
         inline auto and_then(X_lambda&& p_lambda);
+
+    public:
+        inline pointer operator->();
+        inline reference operator*();
+        inline const_pointer operator->() const;
+        inline const_reference operator*() const;
     };
 
 }
diff --git a/include/asyncpp/core/future.inl b/include/asyncpp/core/future.inl
index 54e81b5..c4b0f6f 100644
--- a/include/asyncpp/core/future.inl
+++ b/include/asyncpp/core/future.inl
@@ -76,6 +76,34 @@ namespace asyncpp
         ::and_then(X_lambda&& p_lambda)
         { return trait_type::and_then(std::move(*this), std::forward<X_lambda>(p_lambda)); }
 
+    template<
+        typename T_value,
+        typename T_impl>
+    typename future<T_value, T_impl>::pointer
+    future<T_value, T_impl>::operator->()
+        { return &ref; }
+
+    template<
+        typename T_value,
+        typename T_impl>
+    typename future<T_value, T_impl>::reference
+    future<T_value, T_impl>::operator*()
+        { return ref; }
+
+    template<
+        typename T_value,
+        typename T_impl>
+    typename future<T_value, T_impl>::const_pointer
+    future<T_value, T_impl>::operator->() const
+        { return &ref; }
+
+    template<
+        typename T_value,
+        typename T_impl>
+    typename future<T_value, T_impl>::const_reference
+    future<T_value, T_impl>::operator*() const
+        { return ref; }
+
     /* misc */
 
     template<typename X_value>
diff --git a/include/asyncpp/core/future.pre.h b/include/asyncpp/core/future.pre.h
index dc6226f..b8c7e77 100644
--- a/include/asyncpp/core/future.pre.h
+++ b/include/asyncpp/core/future.pre.h
@@ -6,14 +6,18 @@ namespace asyncpp
     template<typename T_impl>
     struct future_base
     {
-        template<typename T_future>
-        static inline auto poll(T_future& self) = delete;
+    public:
+        using impl_type = T_impl;
 
-        template<typename T_future, typename T_lambda>
-        static inline auto map(T_future&& self, T_lambda&& p_lambda);
+    public:
+        template<typename X_future>
+        static inline auto poll(X_future& self) = delete;
 
-        template<typename T_future, typename T_lambda>
-        static inline auto and_then(T_future&& self, T_lambda&& p_lambda);
+        template<typename X_future, typename X_lambda>
+        static inline auto map(X_future&& self, X_lambda&& p_lambda);
+
+        template<typename X_future, typename X_lambda>
+        static inline auto and_then(X_future&& self, X_lambda&& p_lambda);
     };
 
     template<typename T, typename = void>
diff --git a/include/asyncpp/core/future/and_then.h b/include/asyncpp/core/future/and_then.h
index 8f15743..fd31566 100644
--- a/include/asyncpp/core/future/and_then.h
+++ b/include/asyncpp/core/future/and_then.h
@@ -2,6 +2,8 @@
 
 #include <memory>
 
+#include <asyncpp/core/future.pre.h>
+
 namespace asyncpp {
 namespace __future {
 
@@ -11,16 +13,16 @@ namespace __future {
     struct and_then_impl
     {
     public:
-        using lambda_type           = T_lambda;
-        using outer_future_type     = T_future;
-        using outer_value_type      = typename outer_future_type::value_type;
-        using inner_future_type     = decltype(as_future(std::declval<lambda_type>()(std::declval<outer_value_type>())));
-        using inner_future_type_ptr = std::unique_ptr<inner_future_type>;
+        using lambda_type               = T_lambda;
+        using first_future_type         = T_future;
+        using first_value_type          = typename first_future_type::value_type;
+        using second_future_type        = decltype(as_future(std::declval<lambda_type>()(std::declval<first_value_type>())));
+        using second_future_type_ptr    = std::unique_ptr<second_future_type>;
 
     public:
         lambda_type             lambda;
-        outer_future_type       outer;
-        inner_future_type_ptr   inner;
+        first_future_type       first;
+        second_future_type_ptr  second;
 
     public:
         /**
@@ -35,3 +37,25 @@ namespace __future {
     };
 
 } }
+
+namespace asyncpp
+{
+
+    /* future_trait for and_then_impl */
+
+    template<
+        typename T_future,
+        typename T_lambda>
+    struct future_trait<__future::and_then_impl<T_future, T_lambda>, void>
+        : public future_base<future<__future::and_then_impl<T_future, T_lambda>, void>>
+    {
+        using and_then_type      = __future::and_then_impl<T_future, T_lambda>;
+        using second_future_type = typename and_then_type::second_future_type;
+        using value_type         = typename second_future_type::value_type;
+        using result_type        = typename second_future_type::result_type;
+
+        template<typename X_future>
+        static inline auto poll(X_future& self);
+    };
+
+}
diff --git a/include/asyncpp/core/future/and_then.inl b/include/asyncpp/core/future/and_then.inl
index f7c513d..997133f 100644
--- a/include/asyncpp/core/future/and_then.inl
+++ b/include/asyncpp/core/future/and_then.inl
@@ -2,45 +2,6 @@
 
 #include "map.h"
 
-namespace asyncpp
-{
-
-    /* future_trait for ant_then_impl */
-
-    template<
-        typename T_future,
-        typename T_lambda>
-    struct future_trait<__future::and_then_impl<T_future, T_lambda>, void>
-        : public future_base<future<__future::and_then_impl<T_future, T_lambda>, void>>
-    {
-        using and_then_type     = __future::and_then_impl<T_future, T_lambda>;
-        using inner_future_type = typename and_then_type::inner_future_type;
-        using value_type        = typename inner_future_type::value_type;
-        using result_type       = typename inner_future_type::result_type;
-
-        template<typename X_future>
-        static inline auto poll(X_future& self)
-        {
-            while (true)
-            {
-                if (self.ref.inner)
-                {
-                    return self.ref.inner->poll();
-                }
-                else
-                {
-                    auto r = self.ref.outer.poll();
-                    if (!r)
-                        return result_type::not_ready();
-
-                    self.ref.inner = std::make_unique<inner_future_type>(as_future(self.ref.lambda(*r)));
-                }
-            }
-        }
-    };
-
-}
-
 namespace asyncpp {
 namespace __future {
 
@@ -54,10 +15,42 @@ namespace __future {
         typename X_lambda>
     and_then_impl<T_future, T_lambda>
         ::and_then_impl(
-            X_future&& p_outer,
+            X_future&& p_first,
             X_lambda&& p_lambda)
-        : outer (std::forward<X_future>(p_outer))
+        : first (std::forward<X_future>(p_first))
         , lambda(std::forward<X_lambda>(p_lambda))
         { }
 
 } }
+
+namespace asyncpp
+{
+
+    /* future_trait for ant_then_impl */
+
+    template<
+        typename T_future,
+        typename T_lambda>
+    template<
+        typename X_future>
+    auto future_trait<__future::and_then_impl<T_future, T_lambda>, void>
+        ::poll(X_future& self)
+    {
+        while (true)
+        {
+            if (self->second)
+            {
+                return self->second->poll();
+            }
+            else
+            {
+                auto r = self->first.poll();
+                if (!r)
+                    return result_type::not_ready();
+
+                self->second = std::make_unique<second_future_type>(as_future(self->lambda(*r)));
+            }
+        }
+    }
+
+}
diff --git a/include/asyncpp/core/future/map.h b/include/asyncpp/core/future/map.h
index 030bf74..f3e026b 100644
--- a/include/asyncpp/core/future/map.h
+++ b/include/asyncpp/core/future/map.h
@@ -29,3 +29,26 @@ namespace __future {
     };
 
 } }
+
+namespace asyncpp
+{
+
+    /* future_trait for map_impl */
+
+    template<
+        typename T_future,
+        typename T_lambda>
+    struct future_trait<__future::map_impl<T_future, T_lambda>, void>
+        : public future_base<future<__future::map_impl<T_future, T_lambda>, void>>
+    {
+        using future_type       = T_future;
+        using inner_value_type  = typename future_type::value_type;
+        using lambda_type       = T_lambda;
+        using value_type        = decltype(std::declval<lambda_type>()(std::declval<inner_value_type>()));
+        using result_type       = future_result<value_type>;
+
+        template<typename X_future>
+        static inline auto poll(X_future& self);
+    };
+
+}
diff --git a/include/asyncpp/core/future/map.inl b/include/asyncpp/core/future/map.inl
index 9dd2558..8f32a52 100644
--- a/include/asyncpp/core/future/map.inl
+++ b/include/asyncpp/core/future/map.inl
@@ -2,35 +2,6 @@
 
 #include "map.h"
 
-namespace asyncpp
-{
-
-    /* future_trait for map_impl */
-
-    template<
-        typename T_future,
-        typename T_lambda>
-    struct future_trait<__future::map_impl<T_future, T_lambda>, void>
-        : public future_base<future<__future::map_impl<T_future, T_lambda>, void>>
-    {
-        using future_type       = T_future;
-        using inner_value_type  = typename future_type::value_type;
-        using lambda_type       = T_lambda;
-        using value_type        = decltype(std::declval<lambda_type>()(std::declval<inner_value_type>()));
-        using result_type       = future_result<value_type>;
-
-        template<typename X_future>
-        static inline auto poll(X_future& self)
-        {
-            auto r = self.ref.future.poll();
-            return r
-                ? result_type::ready(self.ref.lambda(*r))
-                : result_type::not_ready();
-        }
-    };
-
-}
-
 namespace asyncpp {
 namespace __future {
 
@@ -51,3 +22,24 @@ namespace __future {
         { }
 
 } }
+
+namespace asyncpp
+{
+
+    /* future_trait for map_impl */
+
+    template<
+        typename T_future,
+        typename T_lambda>
+    template<
+        typename X_future>
+    auto future_trait<__future::map_impl<T_future, T_lambda>, void>
+        ::poll(X_future& self)
+    {
+        auto r = self->future.poll();
+        return r
+            ? result_type::ready(self->lambda(*r))
+            : result_type::not_ready();
+    }
+
+}
diff --git a/include/asyncpp/core/misc.h b/include/asyncpp/core/misc.h
index 6f5acd3..4eede91 100644
--- a/include/asyncpp/core/misc.h
+++ b/include/asyncpp/core/misc.h
@@ -17,4 +17,12 @@ namespace asyncpp
      */
     inline time_point now();
 
+    /**
+     * @brief Returns the lowest of the two passed deadlines (if not null)
+     *        or nullptr if no deadline was passed.
+     */
+    inline const time_point * merge_deadlines(
+        const time_point * p_deadline_0,
+        const time_point * p_deadline_1);
+
 }
diff --git a/include/asyncpp/core/misc.inl b/include/asyncpp/core/misc.inl
index 2ead92a..f969fd7 100644
--- a/include/asyncpp/core/misc.inl
+++ b/include/asyncpp/core/misc.inl
@@ -10,4 +10,28 @@ namespace timer {
         { return clock::now(); }
     #endif
 
+    const time_point * merge_deadlines(
+        const time_point * p_deadline_0,
+        const time_point * p_deadline_1)
+    {
+        if (p_deadline_0 && p_deadline_1)
+        {
+            return *p_deadline_0 < *p_deadline_1
+                ? p_deadline_0
+                : p_deadline_1;
+        }
+        else if (p_deadline_0)
+        {
+            return p_deadline_0;
+        }
+        else if (p_deadline_1)
+        {
+            return p_deadline_1;
+        }
+        else
+        {
+            return nullptr;
+        }
+    }
+
 } }
diff --git a/include/asyncpp/core/stream.h b/include/asyncpp/core/stream.h
index 31ff054..a37d3b5 100644
--- a/include/asyncpp/core/stream.h
+++ b/include/asyncpp/core/stream.h
@@ -5,6 +5,8 @@
 #include "result.h"
 #include "stream.pre.h"
 
+#include "stream/for_each.h"
+
 namespace asyncpp
 {
 
@@ -18,6 +20,10 @@ namespace asyncpp
         using trait_type        = stream_trait<clean_object_type>;
         using value_type        = typename trait_type::value_type;
         using result_type       = stream_result<value_type>;
+        using reference         = clean_object_type&;
+        using pointer           = clean_object_type*;
+        using const_reference   = const clean_object_type&;
+        using const_pointer     = const clean_object_type*;
 
         object_type ref;
 
@@ -31,6 +37,20 @@ namespace asyncpp
          * @brief Function that will be called repeatedly to check if the stream has values.
          */
         inline result_type poll();
+
+        /**
+         * @brief Execute the given lambda for each element in the stream.
+         *
+         * @return Returns a future that completes once the stream is finished.
+         */
+        template<typename X_lambda>
+        inline auto for_each(X_lambda&& p_lambda);
+
+    public:
+        inline pointer operator->();
+        inline reference operator*();
+        inline const_pointer operator->() const;
+        inline const_reference operator*() const;
     };
 
 }
diff --git a/include/asyncpp/core/stream.inl b/include/asyncpp/core/stream.inl
index 434286c..51550e7 100644
--- a/include/asyncpp/core/stream.inl
+++ b/include/asyncpp/core/stream.inl
@@ -2,9 +2,27 @@
 
 #include "stream.h"
 
+#include "stream/for_each.inl"
+
 namespace asyncpp
 {
 
+    /* stream_base */
+
+    template<typename T_impl>
+    template<typename X_stream, typename X_lambda>
+    auto stream_base<T_impl>
+        ::for_each(X_stream&& self, X_lambda&& p_lambda)
+    {
+        using stream_type   = X_stream;
+        using lambda_type   = X_lambda;
+        using for_each_type = __stream::for_each_impl<stream_type, lambda_type>;
+
+        return as_future(for_each_type(
+            std::forward<X_stream>(self),
+            std::forward<X_lambda>(p_lambda)));
+    }
+
     /* stream */
 
     template<
@@ -25,6 +43,43 @@ namespace asyncpp
         ::poll()
         { return trait_type::poll(*this); }
 
+    template<
+        typename T_value,
+        typename T_impl>
+    template<
+        typename X_lambda>
+    auto stream<T_value, T_impl>
+        ::for_each(X_lambda&& p_lambda)
+        { return trait_type::for_each(std::move(*this), std::forward<X_lambda>(p_lambda)); }
+
+    template<
+        typename T_value,
+        typename T_impl>
+    typename stream<T_value, T_impl>::pointer
+    stream<T_value, T_impl>::operator->()
+        { return &ref; }
+
+    template<
+        typename T_value,
+        typename T_impl>
+    typename stream<T_value, T_impl>::reference
+    stream<T_value, T_impl>::operator*()
+        { return ref; }
+
+    template<
+        typename T_value,
+        typename T_impl>
+    typename stream<T_value, T_impl>::const_pointer
+    stream<T_value, T_impl>::operator->() const
+        { return &ref; }
+
+    template<
+        typename T_value,
+        typename T_impl>
+    typename stream<T_value, T_impl>::const_reference
+    stream<T_value, T_impl>::operator*() const
+        { return ref; }
+
     /* misc */
 
     template<typename X_value>
diff --git a/include/asyncpp/core/stream.pre.h b/include/asyncpp/core/stream.pre.h
index 95ad1c9..40a8738 100644
--- a/include/asyncpp/core/stream.pre.h
+++ b/include/asyncpp/core/stream.pre.h
@@ -6,8 +6,15 @@ namespace asyncpp
     template<typename T_impl>
     struct stream_base
     {
-        template<typename T_stream>
-        static inline auto poll(T_stream& self) = delete;
+    public:
+        using impl_type = T_impl;
+
+    public:
+        template<typename X_stream>
+        static inline auto poll(X_stream& self) = delete;
+
+        template<typename X_stream, typename X_lambda>
+        static inline auto for_each(X_stream&& self, X_lambda&& p_lambda);
     };
 
     template<typename T, typename = void>
diff --git a/include/asyncpp/core/stream/for_each.h b/include/asyncpp/core/stream/for_each.h
new file mode 100644
index 0000000..81a490f
--- /dev/null
+++ b/include/asyncpp/core/stream/for_each.h
@@ -0,0 +1,56 @@
+#pragma once
+
+#include <asyncpp/core/future.pre.h>
+
+namespace asyncpp {
+namespace __stream {
+
+    template<
+        typename T_stream,
+        typename T_lambda>
+    struct for_each_impl
+    {
+    public:
+        using stream_type = T_stream;
+        using lambda_type = T_lambda;
+
+    public:
+        stream_type stream;
+        lambda_type lambda;
+
+    public:
+        /**
+         * @brief Constructor.
+         */
+        template<
+            typename X_stream,
+            typename X_lambda>
+        inline for_each_impl(
+            X_stream&& p_stream,
+            X_lambda&& p_lambda);
+    };
+
+} }
+
+namespace asyncpp
+{
+
+    /* future_trait for map_impl */
+
+    template<
+        typename T_stream,
+        typename T_lambda>
+    struct future_trait<__stream::for_each_impl<T_stream, T_lambda>, void>
+        : public future_base<future<__stream::for_each_impl<T_stream, T_lambda>, void>>
+    {
+        using stream_type       = T_stream;
+        using inner_value_type  = typename stream_type::value_type;
+        using lambda_type       = T_lambda;
+        using value_type        = decltype(std::declval<lambda_type>()(std::declval<inner_value_type>()));
+        using result_type       = future_result<value_type>;
+
+        template<typename X_future>
+        static inline auto poll(X_future& self);
+    };
+
+}
diff --git a/include/asyncpp/core/stream/for_each.inl b/include/asyncpp/core/stream/for_each.inl
new file mode 100644
index 0000000..004d72d
--- /dev/null
+++ b/include/asyncpp/core/stream/for_each.inl
@@ -0,0 +1,52 @@
+#pragma once
+
+#include "for_each.h"
+
+namespace asyncpp {
+namespace __stream {
+
+    /* for_each_impl */
+
+    template<
+        typename T_stream,
+        typename T_lambda>
+    template<
+        typename X_stream,
+        typename X_lambda>
+    for_each_impl<T_stream, T_lambda>
+        ::for_each_impl(
+            X_stream&& p_stream,
+            X_lambda&& p_lambda)
+        : stream(std::forward<X_stream>(p_stream))
+        , lambda(std::forward<X_lambda>(p_lambda))
+        { }
+
+} }
+
+namespace asyncpp
+{
+
+    /* future_trait for for_each_impl */
+
+    template<
+        typename T_stream,
+        typename T_lambda>
+    template<
+        typename X_stream>
+    auto future_trait<__stream::for_each_impl<T_stream, T_lambda>, void>
+        ::poll(X_stream& self)
+    {
+        while (true)
+        {
+            auto r = self->stream.poll();
+            if (r.is_done())
+                return result_type::ready();
+
+            if (r.is_not_ready())
+                return result_type::not_ready();
+
+            self->lambda(*r);
+        }
+    }
+
+}
diff --git a/include/asyncpp/core/task.h b/include/asyncpp/core/task.h
index 3aa4ba2..3aa2cc5 100644
--- a/include/asyncpp/core/task.h
+++ b/include/asyncpp/core/task.h
@@ -1,88 +1,9 @@
 #pragma once
 
-#include <vector>
-#include <memory>
-#include <functional>
+#include "task/task.h"
+#include "task/task_tpl.h"
+#include "task/current_task_lock.h"
 
-namespace asyncpp
-{
-
-    struct task
-    {
-    public:
-        using notify_handler        = std::function<void (task&)>;
-        using notify_handler_vector = std::vector<notify_handler>;
-
-    private:
-        bool                    _notified;
-        notify_handler_vector   _notify_handlers;
-
-    public:
-        /**
-         * @brief Destructor.
-         */
-        virtual ~task() = default;
-
-        /**
-         * @brief Check if the task is notified.
-         */
-        inline bool notified() const;
-
-        /**
-         * @brief Notify the task that a resource that the task is interested in, is ready to be polled.
-         */
-        inline void notify();
-
-        /**
-         * @brief Poll the future stored in the task.
-         *
-         * @return TRUE if the task is finished, FALSE otherwise.
-         */
-        inline bool poll();
-
-        /**
-         * @brief Add a callback to execute when the task is notified.
-         */
-        inline void add_notify_handler(notify_handler p_handler);
-
-    private:
-        /**
-         * @brief Actual implementation of the poll function.
-         */
-        virtual bool poll_impl() = 0;
-    };
-
-    template<typename T_future>
-    struct task_tpl
-        : public task
-    {
-    public:
-        using future_type = T_future;
-
-    private:
-        future_type _future;
-
-    public:
-        /**
-         * @brief Constructor.
-         */
-        template<typename X_future>
-        inline task_tpl(X_future&& p_future);
-
-    private:
-        /**
-         * @brief Actual implementation of the poll function.
-         */
-        inline bool poll_impl() override;
-    };
-
-    using task_ptr_w = std::weak_ptr<task>;
-    using task_ptr_s = std::shared_ptr<task>;
-
-    /**
-     * @brief Create a task from the passed future.
-     */
-    template<typename X_future>
-    inline task_ptr_s make_task(X_future&& p_future);
-
-}
+#include "task/task.inl"
+#include "task/task_tpl.inl"
+#include "task/current_task_lock.inl"
diff --git a/include/asyncpp/core/task/current_task_lock.h b/include/asyncpp/core/task/current_task_lock.h
new file mode 100644
index 0000000..481b9a5
--- /dev/null
+++ b/include/asyncpp/core/task/current_task_lock.h
@@ -0,0 +1,23 @@
+#pragma once
+
+#include "task.h"
+#include "current_task_lock.pre.h"
+
+namespace asyncpp
+{
+
+    struct current_task_lock
+    {
+    public:
+        /**
+         * @brief Constructor.
+         */
+        current_task_lock(const task_ptr_s& p_task);
+
+        /**
+         * @brief Destructor.
+         */
+        ~current_task_lock();
+    };
+
+}
diff --git a/include/asyncpp/core/task/current_task_lock.inl b/include/asyncpp/core/task/current_task_lock.inl
new file mode 100644
index 0000000..4367570
--- /dev/null
+++ b/include/asyncpp/core/task/current_task_lock.inl
@@ -0,0 +1,16 @@
+#pragma once
+
+#include "current_task_lock.h"
+
+namespace asyncpp
+{
+
+    /* current_task_lock */
+
+    current_task_lock::current_task_lock(const task_ptr_s& p_task)
+        { task::local_storage().current = p_task; }
+
+    current_task_lock::~current_task_lock()
+        { task::local_storage().current.reset(); }
+
+}
diff --git a/include/asyncpp/core/task/current_task_lock.pre.h b/include/asyncpp/core/task/current_task_lock.pre.h
new file mode 100644
index 0000000..3ebedf2
--- /dev/null
+++ b/include/asyncpp/core/task/current_task_lock.pre.h
@@ -0,0 +1,8 @@
+#pragma once
+
+namespace asyncpp
+{
+
+    struct current_task_lock;
+
+}
diff --git a/include/asyncpp/core/task/task.h b/include/asyncpp/core/task/task.h
new file mode 100644
index 0000000..438ec3d
--- /dev/null
+++ b/include/asyncpp/core/task/task.h
@@ -0,0 +1,76 @@
+#pragma once
+
+#include <vector>
+#include <functional>
+
+#include "task.pre.h"
+#include "current_task_lock.pre.h"
+
+namespace asyncpp
+{
+
+    struct task
+    {
+    public:
+        friend current_task_lock;
+
+        using notify_handler        = std::function<void (task&)>;
+        using notify_handler_vector = std::vector<notify_handler>;
+
+    private:
+        bool                    _notified;
+        notify_handler_vector   _notify_handlers;
+
+    public:
+        /**
+         * @brief Destructor.
+         */
+        virtual ~task() = default;
+
+        /**
+         * @brief Check if the task is notified.
+         */
+        inline bool notified() const;
+
+        /**
+         * @brief Notify the task that a resource that the task is interested in, is ready to be polled.
+         */
+        inline void notify();
+
+        /**
+         * @brief Poll the future stored in the task.
+         *
+         * @return TRUE if the task is finished, FALSE otherwise.
+         */
+        inline bool poll();
+
+        /**
+         * @brief Add a callback to execute when the task is notified.
+         */
+        inline void add_notify_handler(notify_handler p_handler);
+
+    public:
+        /**
+         * @brief Get reference of the current task.
+         */
+        static inline const task_ptr_w& current();
+
+    private:
+        /**
+         * @brief Actual implementation of the poll function.
+         */
+        virtual bool poll_impl() = 0;
+
+    private:
+        struct storage
+        {
+            task_ptr_w current;
+        };
+
+        /**
+         * @brief Get the thread local storage.
+         */
+        static storage& local_storage();
+    };
+
+}
diff --git a/include/asyncpp/core/task/task.inl b/include/asyncpp/core/task/task.inl
new file mode 100644
index 0000000..0ce239a
--- /dev/null
+++ b/include/asyncpp/core/task/task.inl
@@ -0,0 +1,37 @@
+#pragma once
+
+namespace asyncpp
+{
+
+    /* task */
+
+    bool task::poll()
+    {
+        _notified = false;
+        return poll_impl();
+    }
+
+    bool task::notified() const
+        { return _notified; }
+
+    void task::notify()
+    {
+        _notified = true;
+
+        for (auto& h : _notify_handlers)
+            h(*this);
+    }
+
+    void task::add_notify_handler(notify_handler p_handler)
+        { _notify_handlers.emplace_back(p_handler); }
+
+    const task_ptr_w& task::current()
+        { return local_storage().current; }
+
+    task::storage& task::local_storage()
+    {
+        thread_local storage value { };
+        return value;
+    }
+
+}
diff --git a/include/asyncpp/core/task/task.pre.h b/include/asyncpp/core/task/task.pre.h
new file mode 100644
index 0000000..6780a6b
--- /dev/null
+++ b/include/asyncpp/core/task/task.pre.h
@@ -0,0 +1,13 @@
+#pragma once
+
+#include <memory>
+
+namespace asyncpp
+{
+
+    struct task;
+
+    using task_ptr_w = std::weak_ptr<task>;
+    using task_ptr_s = std::shared_ptr<task>;
+
+}
diff --git a/include/asyncpp/core/task/task_tpl.h b/include/asyncpp/core/task/task_tpl.h
new file mode 100644
index 0000000..f6663b7
--- /dev/null
+++ b/include/asyncpp/core/task/task_tpl.h
@@ -0,0 +1,32 @@
+#pragma once
+
+#include "task.h"
+
+namespace asyncpp
+{
+
+    template<typename T_future>
+    struct task_tpl
+        : public task
+    {
+    public:
+        using future_type = T_future;
+
+    private:
+        future_type _future;
+
+    public:
+        /**
+         * @brief Constructor.
+         */
+        template<typename X_future>
+        inline task_tpl(X_future&& p_future);
+
+    private:
+        /**
+         * @brief Actual implementation of the poll function.
+         */
+        inline bool poll_impl() override;
+    };
+
+}
diff --git a/include/asyncpp/core/task.inl b/include/asyncpp/core/task/task_tpl.inl
similarity index 59%
rename from include/asyncpp/core/task.inl
rename to include/asyncpp/core/task/task_tpl.inl
index 97c7ab4..908c63e 100644
--- a/include/asyncpp/core/task.inl
+++ b/include/asyncpp/core/task/task_tpl.inl
@@ -1,30 +1,10 @@
 #pragma once
 
+#include "task_tpl.h"
+
 namespace asyncpp
 {
 
-    /* task */
-
-    bool task::poll()
-    {
-        _notified = false;
-        return poll_impl();
-    }
-
-    bool task::notified() const
-        { return _notified; }
-
-    void task::notify()
-    {
-        _notified = true;
-
-        for (auto& h : _notify_handlers)
-            h(*this);
-    }
-
-    void task::add_notify_handler(notify_handler p_handler)
-        { _notify_handlers.emplace_back(p_handler); }
-
     /* task_tpl */
 
     template<typename T_future>
diff --git a/include/asyncpp/executor/current_thread.inl b/include/asyncpp/executor/current_thread.inl
index 8a57dfb..73a2c37 100644
--- a/include/asyncpp/executor/current_thread.inl
+++ b/include/asyncpp/executor/current_thread.inl
@@ -8,24 +8,6 @@ namespace executor {
     namespace __impl
     {
 
-        struct current_task_lock
-        {
-        private:
-            executor::storage& _storage;
-
-        public:
-            current_task_lock(
-                executor::storage&  p_storage,
-                const task_ptr_s&   p_task)
-                : _storage  (p_storage)
-            {
-                _storage.current_task = p_task;
-            }
-
-            ~current_task_lock()
-                { _storage.current_task.reset(); }
-        };
-
         struct current_executor_lock
         {
         private:
@@ -37,11 +19,11 @@ namespace executor {
                 executor&           p_executor)
                 : _storage  (p_storage)
             {
-                _storage.current_executor = &p_executor;
+                _storage.current = &p_executor;
             }
 
             ~current_executor_lock()
-                { _storage.current_executor = nullptr; }
+                { _storage.current = nullptr; }
         };
 
     }
@@ -100,7 +82,7 @@ namespace executor {
     void current_thread<T_runtime>
         ::poll_task(task_ptr_s p_task)
     {
-        __impl::current_task_lock l(executor::local_storage(), p_task);
+        current_task_lock l(p_task);
 
         // TODO execption handling
 
diff --git a/include/asyncpp/executor/executor.h b/include/asyncpp/executor/executor.h
index 33789fd..50a6f9d 100644
--- a/include/asyncpp/executor/executor.h
+++ b/include/asyncpp/executor/executor.h
@@ -10,16 +10,10 @@ namespace executor {
     public:
         struct storage
         {
-            task_ptr_w  current_task;
-            executor *  current_executor;
+            executor *  current;
         };
 
     public:
-        /**
-         * @brief Get reference of the current task.
-         */
-        static inline const task_ptr_w& current_task();
-
         /**
          * @brief Spawn a new task.
          */
diff --git a/include/asyncpp/executor/executor.inl b/include/asyncpp/executor/executor.inl
index ed6c7b8..385342b 100644
--- a/include/asyncpp/executor/executor.inl
+++ b/include/asyncpp/executor/executor.inl
@@ -7,13 +7,10 @@ namespace executor {
 
     /* executor */
 
-    const task_ptr_w& executor::current_task()
-        { return local_storage().current_task; }
-
     template<typename X_future>
     void executor::spawn(X_future&& p_future)
     {
-        auto exec = local_storage().current_executor;
+        auto exec = local_storage().current;
         if (!exec)
             throw std::runtime_error("Thread local executor instance is not assigned!");
         exec->spawn_impl(make_task(std::forward<X_future>(p_future)));
diff --git a/include/asyncpp/timer.h b/include/asyncpp/timer.h
index e90e6c3..f8898b7 100644
--- a/include/asyncpp/timer.h
+++ b/include/asyncpp/timer.h
@@ -1,7 +1,9 @@
 #pragma once
 
 #include "timer/delay.h"
+#include "timer/interval.h"
 #include "timer/timer.h"
 
 #include "timer/delay.inl"
+#include "timer/interval.inl"
 #include "timer/timer.inl"
diff --git a/include/asyncpp/timer/delay.h b/include/asyncpp/timer/delay.h
index c90b7f4..5b04065 100644
--- a/include/asyncpp/timer/delay.h
+++ b/include/asyncpp/timer/delay.h
@@ -14,14 +14,14 @@ namespace timer {
         friend struct future_trait<delay, void>;
 
     private:
-        time_point              _timeout;
-        __impl::registration    _registration;
+        time_point                  _deadline;
+        __impl::registration_ptr_w  _registration;
 
     public:
         /**
-         * @brief Constructor. Create a delay at the given timeout.
+         * @brief Constructor. Create a delay at the given deadline.
          */
-        inline delay(const time_point& p_timeout);
+        inline delay(const time_point& p_deadline);
 
         /**
          * @brief Constructor. Create a delay with the given duration.
@@ -35,14 +35,14 @@ namespace timer {
         inline ~delay();
 
         /**
-         * @brief Get the current timeout of the delay.
+         * @brief Get the current deadline of the delay.
          */
-        inline time_point timeout() const;
+        inline time_point deadline() const;
 
         /**
          * @brief Reset the delay to a new time point.
          */
-        inline void reset(const time_point& p_timeout);
+        inline void reset(const time_point& p_deadline);
 
         /**
          * @brief Reset the delay to the given duration.
@@ -52,3 +52,21 @@ namespace timer {
     };
 
 } }
+
+namespace asyncpp
+{
+
+    /* future_impl for timer::delay */
+
+    template<>
+    struct future_trait<timer::delay, void>
+        : public future_base<future<timer::delay, void>>
+    {
+        using value_type    = void;
+        using result_type   = future_result<value_type>;
+
+        template<typename X_future>
+        static inline auto poll(X_future& self);
+    };
+
+}
diff --git a/include/asyncpp/timer/delay.inl b/include/asyncpp/timer/delay.inl
index e127a9e..b731218 100644
--- a/include/asyncpp/timer/delay.inl
+++ b/include/asyncpp/timer/delay.inl
@@ -12,34 +12,34 @@ namespace timer {
 
     /* delay */
 
-    delay::delay(const time_point& p_timeout)
-        : _timeout      (p_timeout)
-        , _registration (*this)
+    delay::delay(const time_point& p_deadline)
+        : _deadline     (p_deadline)
+        , _registration ()
         { }
 
     template<typename T_base, typename T_ratio>
     delay::delay(const duration<T_base, T_ratio>& p_duration)
-        : _timeout      (clock::now() + p_duration)
-        , _registration (*this)
+        : _deadline     (clock::now() + p_duration)
+        , _registration ()
         { }
 
     inline delay::~delay()
         { __impl::timer_base::unregister_resource(_registration); }
 
-    time_point delay::timeout() const
-        { return _timeout; }
+    time_point delay::deadline() const
+        { return _deadline; }
 
-    void delay::reset(const time_point& p_timeout)
+    void delay::reset(const time_point& p_deadline)
     {
         __impl::timer_base::unregister_resource(_registration);
-        _timeout = p_timeout;
+        _deadline = p_deadline;
     }
 
     template<typename T_base, typename T_ratio>
     void delay::reset(const duration<T_base, T_ratio>& p_duration)
     {
         __impl::timer_base::unregister_resource(_registration);
-        _timeout = now() + p_duration;
+        _deadline = now() + p_duration;
     }
 
 } }
@@ -49,25 +49,19 @@ namespace asyncpp
 
     /* future_impl for timer::delay */
 
-    template<>
-    struct future_trait<timer::delay, void>
-        : public future_base<future<timer::delay, void>>
+    template<typename X_future>
+    auto future_trait<timer::delay, void>
+        ::poll(X_future& self)
     {
-        using value_type    = void;
-        using result_type   = future_result<value_type>;
+        auto now = timer::now();
 
-        template<typename X_future>
-        static inline auto poll(X_future& self)
-        {
-            auto now = timer::now();
+        if (self->_deadline <= now)
+            return result_type::ready();
 
-            if (self.ref._timeout <= now)
-                return result_type::ready();
+        if (self->_registration.expired())
+            self->_registration = timer::__impl::timer_base::register_resource(self->_deadline);
 
-            timer::__impl::timer_base::register_resource(self.ref._registration);
-
-            return result_type::not_ready();
-        }
-    };
+        return result_type::not_ready();
+    }
 
 }
diff --git a/include/asyncpp/timer/impl/registration.h b/include/asyncpp/timer/impl/registration.h
index 87fa320..add261f 100644
--- a/include/asyncpp/timer/impl/registration.h
+++ b/include/asyncpp/timer/impl/registration.h
@@ -3,9 +3,9 @@
 #include <memory>
 
 #include <asyncpp/core/misc.h>
+#include <asyncpp/core/task.h>
 
 #include "timer_base.pre.h"
-#include "../delay.pre.h"
 
 namespace asyncpp {
 namespace timer {
@@ -14,27 +14,20 @@ namespace __impl {
     struct registration
     {
     public:
-        struct inner
-        {
-            timer_base&     owner;
-            time_point      timeout;
-
-            /**
-             * @brief Constructor.
-             */
-            inline inner(timer_base& p_owner, time_point p_timeout);
-        };
-
-        using inner_ptr_w = std::weak_ptr<inner>;
-
-    public:
-        delay&      owner;
-        inner_ptr_w ptr;
+        timer_base&         owner;
+        const time_point    deadline;
+        const task_ptr_w    task;
 
         /**
          * @brief Constructor.
          */
-        inline registration(delay& p_owner);
+        inline registration(
+            timer_base&         p_owner,
+            const time_point&   p_deadline,
+            const task_ptr_w&   p_task);
     };
 
+    using registration_ptr_w = std::weak_ptr<registration>;
+    using registration_ptr_s = std::shared_ptr<registration>;
+
 } } }
diff --git a/include/asyncpp/timer/impl/registration.inl b/include/asyncpp/timer/impl/registration.inl
index b0516d1..477bdc9 100644
--- a/include/asyncpp/timer/impl/registration.inl
+++ b/include/asyncpp/timer/impl/registration.inl
@@ -6,18 +6,15 @@ namespace asyncpp {
 namespace timer {
 namespace __impl {
 
-    /* registration::inner */
-
-    registration::inner::inner(timer_base& p_owner, time_point p_timeout)
-        : owner     (p_owner)
-        , timeout   (p_timeout)
-        { }
-
     /* registration */
 
-    registration::registration(delay& p_owner)
-        : owner(p_owner)
-        , ptr  ()
+    registration::registration(
+        timer_base&         p_owner,
+        const time_point&   p_deadline,
+        const task_ptr_w&   p_task)
+        : owner     (p_owner)
+        , deadline  (p_deadline)
+        , task      (p_task)
         { }
 
 } } }
diff --git a/include/asyncpp/timer/impl/registration.pre.h b/include/asyncpp/timer/impl/registration.pre.h
deleted file mode 100644
index f4274b3..0000000
--- a/include/asyncpp/timer/impl/registration.pre.h
+++ /dev/null
@@ -1,9 +0,0 @@
-#pragma once
-
-namespace asyncpp {
-namespace timer {
-namespace __impl {
-
-    struct registration;
-
-} } }
diff --git a/include/asyncpp/timer/impl/timer_base.h b/include/asyncpp/timer/impl/timer_base.h
index 00921c2..dc364ed 100644
--- a/include/asyncpp/timer/impl/timer_base.h
+++ b/include/asyncpp/timer/impl/timer_base.h
@@ -17,15 +17,17 @@ namespace __impl {
     struct timer_base
     {
     private:
-        using inner_ptr_s = std::shared_ptr<registration::inner>;
-
-        struct inner_less_compare
-            { constexpr bool operator()(const inner_ptr_s& lhs, const inner_ptr_s& rhs) const; };
+        struct registration_less_compare
+        {
+            constexpr bool operator()(
+                const registration_ptr_s& lhs,
+                const registration_ptr_s& rhs) const;
+        };
 
-        using inner_set = std::set<inner_ptr_s, inner_less_compare>;
+        using registration_set = std::set<registration_ptr_s, registration_less_compare>;
 
     protected:
-        cppcore::locked<inner_set> _registrations;
+        cppcore::locked<registration_set> _registrations;
 
     public:
         /**
@@ -58,18 +60,18 @@ namespace __impl {
         /**
          * @brief Register a new resource within this timer_base.
          */
-        static inline void register_resource(registration& p_value);
+        static inline registration_ptr_w register_resource(const time_point& p_deadline);
 
         /**
          * @brief Register a new resource within this timer_base.
          */
-        static inline void unregister_resource(registration& p_value);
+        static inline void unregister_resource(registration_ptr_w& p_value);
 
     private:
         /**
-         * @brief Add a new resource to the timer_base.
+         * @brief Create registration for a new resource.
          */
-        inline inner_ptr_s make_inner(registration& p_value);
+        registration_ptr_w create_registration(const time_point& p_deadline);
 
     private:
         struct storage
diff --git a/include/asyncpp/timer/impl/timer_base.inl b/include/asyncpp/timer/impl/timer_base.inl
index bb80eac..af31e96 100644
--- a/include/asyncpp/timer/impl/timer_base.inl
+++ b/include/asyncpp/timer/impl/timer_base.inl
@@ -8,13 +8,15 @@ namespace __impl {
 
     /* timer_base::inner_less_compare */
 
-    constexpr bool timer_base::inner_less_compare::operator()(const inner_ptr_s& lhs, const inner_ptr_s& rhs) const
+    constexpr bool timer_base::registration_less_compare::operator()(
+        const registration_ptr_s& lhs,
+        const registration_ptr_s& rhs) const
     {
-        return  (lhs->timeout <  rhs->timeout)
+        return  (lhs->deadline <  rhs->deadline)
                     ?  true
                     :
-                (lhs->timeout == rhs->timeout)
-            &&  (lhs.get()    <  rhs.get())
+                (lhs->deadline == rhs->deadline)
+            &&  (lhs.get()     <  rhs.get())
                     ?   true
                     :   false;
     }
@@ -50,42 +52,36 @@ namespace __impl {
     timer_base* timer_base::current()
         { return local_storage().current; }
 
-    void timer_base::register_resource(registration& p_value)
+    registration_ptr_w timer_base::register_resource(const time_point& p_deadline)
     {
-        auto s = p_value.ptr.lock();
+        auto t = current();
 
-        if (s && s->timeout != p_value.owner.timeout())
-        {
-            unregister_resource(p_value);
-            s.reset();
-        }
+        if (!t)
+            throw std::runtime_error("Thread local timer_base instance is not assigned!");
 
-        if (!s)
-        {
-            auto t = current();
+        return t->create_registration(p_deadline);
+    }
+
+    registration_ptr_w timer_base::create_registration(const time_point& p_deadline)
+    {
+        auto r = std::make_shared<registration>(
+            *this,
+            p_deadline,
+            task::current());
 
-            if (!t)
-                throw std::runtime_error("Thread local timer_base instance is not assigned!");
+        _registrations.lock()->insert(r);
 
-            p_value.ptr = t->make_inner(p_value);
-        }
+        return r;
     }
 
-    void timer_base::unregister_resource(registration& p_value)
+    void timer_base::unregister_resource(registration_ptr_w& p_value)
     {
-        auto s = p_value.ptr.lock();
-        p_value.ptr.reset();
+        auto s = p_value.lock();
+        p_value.reset();
         if (s)
             s->owner._registrations.lock()->erase(s);
     }
 
-    inline timer_base::inner_ptr_s timer_base::make_inner(registration& p_value)
-    {
-        auto s = std::make_shared<registration::inner>(*this, p_value.owner.timeout());
-        _registrations.lock()->insert(s);
-        return s;
-    }
-
     timer_base::storage& timer_base::local_storage()
     {
         thread_local storage value;
diff --git a/include/asyncpp/timer/interval.h b/include/asyncpp/timer/interval.h
new file mode 100644
index 0000000..10fa2b2
--- /dev/null
+++ b/include/asyncpp/timer/interval.h
@@ -0,0 +1,67 @@
+#pragma once
+
+#include <asyncpp/core/misc.h>
+#include <asyncpp/core/future.h>
+#include <asyncpp/core/stream.h>
+
+#include "delay.h"
+
+namespace asyncpp {
+namespace timer {
+
+    struct interval
+    {
+    public:
+        using delay_future_type = future<delay>;
+
+    public:
+        friend struct stream_trait<interval, void>;
+
+    private:
+        delay_future_type   _delay;     //!< Delay future
+        clock::duration     _duration;  //!< Interval duration.
+        time_point          _deadline;  //!< Deadline after the interval should end.
+
+    public:
+        /**
+         * @brief Constructor.
+         */
+        template<typename T_base, typename T_ratio>
+        inline interval(
+            const duration<T_base, T_ratio>&    p_duration,
+            time_point                          p_deadline = time_point());
+
+        /**
+         * @brief Constructor.
+         */
+        template<typename T_base, typename T_ratio>
+        inline interval(
+            const time_point&                   p_at,
+            const duration<T_base, T_ratio>&    p_duration,
+            time_point                          p_deadline = time_point());
+
+        /**
+         * @brief Get the duration of the interval.
+         */
+        inline const clock::duration& duration() const;
+    };
+
+} }
+
+namespace asyncpp
+{
+
+    /* stream_trait for timer::interval */
+
+    template<>
+    struct stream_trait<timer::interval, void>
+        : public stream_base<stream<timer::interval, void>>
+    {
+        using value_type    = void;
+        using result_type   = stream_result<value_type>;
+
+        template<typename X_stream>
+        static inline result_type poll(X_stream& self);
+    };
+
+}
diff --git a/include/asyncpp/timer/interval.inl b/include/asyncpp/timer/interval.inl
new file mode 100644
index 0000000..3ea1ee4
--- /dev/null
+++ b/include/asyncpp/timer/interval.inl
@@ -0,0 +1,60 @@
+#pragma once
+
+#include <asyncpp/core/future.inl>
+
+#include "delay.inl"
+#include "interval.h"
+
+namespace asyncpp {
+namespace timer {
+
+    /* interval */
+
+    template<typename T_base, typename T_ratio>
+    interval::interval(
+        const asyncpp::duration<T_base, T_ratio>&   p_duration,
+        time_point                                  p_deadline)
+            : interval(clock::now() + p_duration, p_duration, p_deadline)
+            { }
+
+    template<typename T_base, typename T_ratio>
+    interval::interval(
+        const time_point&                           p_at,
+        const asyncpp::duration<T_base, T_ratio>&   p_duration,
+        time_point                                  p_deadline)
+            : _delay   (as_future(delay(p_at)))
+            , _duration(p_duration)
+            , _deadline(p_deadline)
+            { }
+
+    const clock::duration& interval::duration() const
+        { return _duration; }
+
+} }
+
+namespace asyncpp
+{
+
+    /* stream_trait for timer::interval */
+
+    template<typename X_stream>
+    typename stream_trait<timer::interval, void>::result_type
+    stream_trait<timer::interval, void>
+        ::poll(X_stream& self)
+    {
+        auto ret = self->_delay.poll();
+        if (ret.is_not_ready())
+            return result_type::not_ready();
+
+        auto now = self->_delay->deadline();
+        auto new_deadline = now + self->_duration;
+        if (    self->_deadline.time_since_epoch().count()
+            &&  new_deadline >= self->_deadline)
+            return result_type::done();
+
+        self->_delay->reset(new_deadline);
+
+        return result_type::ready();
+    }
+
+}
diff --git a/include/asyncpp/timer/timer.h b/include/asyncpp/timer/timer.h
index 490b305..1aba160 100644
--- a/include/asyncpp/timer/timer.h
+++ b/include/asyncpp/timer/timer.h
@@ -49,23 +49,23 @@ namespace timer {
          * @brief Handle idle of the runtime.
          *
          * This method is called as soon as the runtime has nothing to do.
-         * The passed timeout is the timepoint the method should return (or null if not set).
+         * The passed deadline is the timepoint the method should return (or null if not set).
          */
-        inline void idle(asyncpp::time_point* p_timeout);
+        inline void idle(const asyncpp::time_point * p_deadline);
 
     private:
         /**
          * @brief Call the idle method of the inner runtime.
          */
         template<typename X = inner_type>
-        inline auto inner_idle(asyncpp::time_point* p_timeout)
+        inline auto inner_idle(const asyncpp::time_point * p_deadline)
             -> std::enable_if_t<std::is_same_v<X, void>>;
 
         /**
          * @brief Call the idle method of the inner runtime.
          */
         template<typename X = inner_type>
-        inline auto inner_idle(asyncpp::time_point* p_timeout)
+        inline auto inner_idle(const asyncpp::time_point * p_deadline)
             -> std::enable_if_t<!std::is_same_v<X, void>>;
     };
 
diff --git a/include/asyncpp/timer/timer.inl b/include/asyncpp/timer/timer.inl
index a5f424b..8f65b37 100644
--- a/include/asyncpp/timer/timer.inl
+++ b/include/asyncpp/timer/timer.inl
@@ -1,5 +1,7 @@
 #pragma once
 
+#include <asyncpp/core/misc.inl>
+
 #include "timer.h"
 #include "delay.inl"
 
@@ -37,40 +39,29 @@ namespace timer {
         { }
 
     template<typename T_inner>
-    void timer<T_inner>::idle(asyncpp::time_point* p_timeout)
+    void timer<T_inner>::idle(const asyncpp::time_point * p_deadline)
     {
-        bool has_timeout = false;
-        asyncpp::time_point timeout;
-
-        if (p_timeout)
-        {
-            timeout = *p_timeout;
-            has_timeout = true;
-        }
+        auto now = clock::now();
 
         {
         auto r = _registrations.lock();
-        if (!r->empty())
+        auto it = r->begin();
+        while (it != r->end() && now >= (**it).deadline)
         {
-            auto t = (*r->begin())->timeout;
-
-            if (!has_timeout)
-                timeout = t;
-            else if (t < timeout)
-                timeout = t;
+            auto t = (**it).task.lock();
+            if (t)
+                t->notify();
 
-            has_timeout = true;
+            ++it;
         }
         }
 
-        inner_idle(has_timeout
-            ? &timeout
-            : nullptr);
+        inner_idle(p_deadline);
     }
 
     template<typename T_inner>
     template<typename X>
-    auto timer<T_inner>::inner_idle(asyncpp::time_point* p_timeout)
+    auto timer<T_inner>::inner_idle(const asyncpp::time_point * p_deadline)
         -> std::enable_if_t<std::is_same_v<X, void>>
     {
         /* no-op */
@@ -78,10 +69,18 @@ namespace timer {
 
     template<typename T_inner>
     template<typename X>
-    auto timer<T_inner>::inner_idle(asyncpp::time_point* p_timeout)
+    auto timer<T_inner>::inner_idle(const asyncpp::time_point * p_deadline)
         -> std::enable_if_t<!std::is_same_v<X, void>>
     {
-        _storage.inner.idle(p_timeout);
+        {
+        auto r = _registrations.lock();
+        if (!r->empty())
+        {
+            p_deadline = merge_deadlines(p_deadline, &(*r->begin())->deadline);
+        }
+        }
+
+        _storage.inner.idle(p_deadline);
     }
 
 } }
diff --git a/test/asyncpp/core/future_tests.cpp b/test/asyncpp/core/future_tests.cpp
index 7affd4b..78c8b7f 100644
--- a/test/asyncpp/core/future_tests.cpp
+++ b/test/asyncpp/core/future_tests.cpp
@@ -25,10 +25,10 @@ namespace asyncpp
         {
             using result_type = future_result<value_type>;
 
-            if (self.ref.count >= self.ref.delay)
-                return result_type::ready(self.ref.count);
+            if (self->count >= self->delay)
+                return result_type::ready(self->count);
 
-            ++self.ref.count;
+            ++self->count;
             return result_type::not_ready();
         }
     };
diff --git a/test/asyncpp/core/stream_tests.cpp b/test/asyncpp/core/stream_tests.cpp
index 271266e..1e64fc6 100644
--- a/test/asyncpp/core/stream_tests.cpp
+++ b/test/asyncpp/core/stream_tests.cpp
@@ -17,23 +17,23 @@ namespace asyncpp
 
     template<>
     struct stream_trait<delay, void>
-        : public future_base<future<delay, void>>
+        : public stream_base<stream<delay, void>>
     {
         using value_type = int;
 
-        template<typename T_future>
-        static inline auto poll(T_future& self)
+        template<typename X_stream>
+        static inline auto poll(X_stream& self)
         {
             using result_type = stream_result<value_type>;
 
-            if (self.ref.count >= self.ref.delay)
+            if (self->count >= self->delay)
                 return result_type::done();
 
-            ++self.ref.count;
+            ++self->count;
 
-            return self.ref.count <= self.ref.threshold
+            return self->count <= self->threshold
                 ? result_type::not_ready()
-                : result_type::ready(self.ref.count);
+                : result_type::ready(self->count);
         }
     };
 
@@ -66,3 +66,17 @@ TEST(stream_tests, poll)
     ASSERT_FALSE(r);
     ASSERT_TRUE (r.is_done());
 }
+
+TEST(stream_tests, for_each)
+{
+    int i = 0;
+    delay d { 5, 0, 0 };
+    auto f = as_stream(d)
+        .for_each([&i](int x) {
+            ++i;
+            EXPECT_EQ(i, x);
+        });
+
+    auto r = f.poll();
+    ASSERT_TRUE(r);
+}
diff --git a/test/asyncpp/core/task_tests.cpp b/test/asyncpp/core/task_tests.cpp
index cd36d87..e1ead2e 100644
--- a/test/asyncpp/core/task_tests.cpp
+++ b/test/asyncpp/core/task_tests.cpp
@@ -25,10 +25,10 @@ namespace asyncpp
         {
             using result_type = future_result<value_type>;
 
-            if (self.ref.count >= self.ref.delay)
-                return result_type::ready(self.ref.count);
+            if (self->count >= self->delay)
+                return result_type::ready(self->count);
 
-            ++self.ref.count;
+            ++self->count;
             return result_type::not_ready();
         }
     };
diff --git a/test/asyncpp/executor/current_thread_tests.cpp b/test/asyncpp/executor/current_thread_tests.cpp
index 4e567c3..5972bdf 100644
--- a/test/asyncpp/executor/current_thread_tests.cpp
+++ b/test/asyncpp/executor/current_thread_tests.cpp
@@ -27,8 +27,8 @@ namespace asyncpp
         template<typename X_future>
         static inline auto poll(X_future& self)
         {
-            self.ref.task = executor::executor::current_task();
-            return self.ref.done
+            self->task = task::current();
+            return self->done
                 ? result_type::ready()
                 : result_type::not_ready();
         }
diff --git a/test/asyncpp/timer/interval_tests.cpp b/test/asyncpp/timer/interval_tests.cpp
new file mode 100644
index 0000000..59de013
--- /dev/null
+++ b/test/asyncpp/timer/interval_tests.cpp
@@ -0,0 +1,72 @@
+#include <gtest/gtest.h>
+
+#include "../../helper/now_mock.h"
+
+#include <asyncpp.h>
+#include <asyncpp/timer.h>
+
+using namespace ::testing;
+using namespace ::asyncpp;
+using namespace ::asyncpp::timer;
+
+TEST(interval_tests, poll)
+{
+    InSequence seq;
+    StrictMock<now_mock> m;
+    asyncpp::timer::timer t;
+    interval i(
+        time_point(std::chrono::seconds(10)),
+        std::chrono::seconds(5),
+        time_point(std::chrono::seconds(30)));
+
+    // 30 - 10 = 20
+    // 20 / 5  = 4
+    // 4  - 1  = 3
+    // 3 x Ready
+
+    t.make_current();
+
+    auto s = as_stream(i);
+
+    EXPECT_CALL(m, now)
+        .WillOnce(Return(time_point(std::chrono::seconds(0))));
+
+    auto r0 = s.poll();
+    ASSERT_EQ(result_status::not_ready, r0.status());
+
+    EXPECT_CALL(m, now)
+        .WillOnce(Return(time_point(std::chrono::seconds(9))));
+
+    auto r1 = s.poll();
+    ASSERT_EQ(result_status::not_ready, r1.status());
+
+    EXPECT_CALL(m, now)
+        .WillOnce(Return(time_point(std::chrono::seconds(10))));
+
+    auto r2 = s.poll();
+    ASSERT_EQ(result_status::ready, r2.status());
+
+    EXPECT_CALL(m, now)
+        .WillOnce(Return(time_point(std::chrono::seconds(11))));
+
+    auto r3 = s.poll();
+    ASSERT_EQ(result_status::not_ready, r3.status());
+
+    EXPECT_CALL(m, now)
+        .WillOnce(Return(time_point(std::chrono::seconds(30))));
+
+    auto r4 = s.poll();
+    ASSERT_EQ(result_status::ready, r4.status());
+
+    EXPECT_CALL(m, now)
+        .WillOnce(Return(time_point(std::chrono::seconds(30))));
+
+    auto r5 = s.poll();
+    ASSERT_EQ(result_status::ready, r5.status());
+
+    EXPECT_CALL(m, now)
+        .WillOnce(Return(time_point(std::chrono::seconds(30))));
+
+    auto r6 = s.poll();
+    ASSERT_EQ(result_status::done, r6.status());
+}
diff --git a/test/helper/runtime_mock.h b/test/helper/runtime_mock.h
index 0851f20..935731f 100644
--- a/test/helper/runtime_mock.h
+++ b/test/helper/runtime_mock.h
@@ -8,5 +8,5 @@
 struct runtime_mock
 {
 public:
-    MOCK_METHOD1(idle, void (asyncpp::time_point* p_timeout));
+    MOCK_METHOD1(idle, void (const asyncpp::time_point * p_deadline));
 };