job/monitor: add simple monitor adapter

CMakeLists.txt

@@ -270,6 +270,8 @@ list (
     iterator.hpp
     job/event.hpp
     job/flag.hpp
+    job/monitor.cpp
+    job/monitor.hpp
     job/queue.cpp
     job/queue.hpp
     job/semaphore.hpp
@@ -486,6 +488,7 @@ if (TESTS)
         iterator
         job/event
         job/flag
+        job/monitor
         job/queue
         job/semaphore
         job/spinlock

job/monitor.cpp

@@ -0,0 +1,19 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * Copyright 2018 Danny Robson <danny@nerdcruft.net>
+ */
+
+#include "monitor.hpp"
+
+using util::job::monitor;

job/monitor.hpp

@@ -0,0 +1,60 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * Copyright 2018 Danny Robson <danny@nerdcruft.net>
+ */
+
+#ifndef CRUFT_UTIL_JOB_MONITOR_HPP
+#define CRUFT_UTIL_JOB_MONITOR_HPP
+
+#include <mutex>
+#include <utility>
+#include <functional>
+
+
+namespace util::job {
+    template <typename ValueT, typename MutexT = std::mutex>
+    class monitor {
+    public:
+        template <typename ...Args>
+        monitor (Args &&...args):
+            m_value (std::forward<Args> (args)...)
+        { ; }
+
+        class proxy {
+        public:
+            proxy (MutexT &_mutex, ValueT &_value):
+                m_guard (_mutex),
+                m_value (_value)
+            { ; }
+
+            ValueT* operator-> ()
+            {
+                return &m_value;
+            }
+
+        private:
+            std::lock_guard<MutexT> m_guard;
+            ValueT &m_value;
+        };
+
+        auto acquire (void) { return proxy (m_mutex, m_value); }
+        auto operator-> () { return acquire (); }
+
+    private:
+        MutexT m_mutex;
+        ValueT m_value;
+    };
+};
+
+#endif

test/job/monitor.cpp

@@ -0,0 +1,76 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * Copyright 2018 Danny Robson <danny@nerdcruft.net>
+ */
+
+#include "tap.hpp"
+#include "job/monitor.hpp"
+#include "job/event.hpp"
+#include "job/semaphore.hpp"
+
+#include <atomic>
+#include <thread>
+
+
+///////////////////////////////////////////////////////////////////////////////
+// a single atomic integer wrapper that allows precise ordering of thread
+// entrance and exit for exact testing of thread interleavings.
+struct foo {
+    foo ():
+        enter (0),
+        leave (0)
+    { ; }
+
+    void
+    inc (void) {
+        enter.acquire ();
+        ++value;
+        leave.release ();
+    }
+
+    std::atomic<int> value = 0;
+    util::job::semaphore enter;
+    util::job::semaphore leave;
+};
+
+
+///////////////////////////////////////////////////////////////////////////////
+int
+main ()
+{
+    util::TAP::logger tap;
+
+    util::job::monitor<foo> obj;
+    const auto &value = obj->value;
+    auto &enter = obj->enter;
+    auto &leave = obj->leave;
+
+    std::thread t1 ([&] () { obj->inc (); });
+    std::thread t2 ([&] () { obj->inc (); });
+
+    tap.expect_eq (value, 0, "wrapped class was left initialised");
+
+    enter.release ();
+    leave.acquire ();
+    tap.expect_eq (value, 1, "only one thread had access");
+
+    enter.release ();
+    leave.acquire ();
+    tap.expect_eq (value, 2, "second thread got access");
+
+    t1.join ();
+    t2.join ();
+
+    return tap.status ();
+}