Added Observers interface to Index.

4 files changed, 117 insertions, 0 deletions

diff --git a/base/base.pro b/base/base.pro
index c8c2287523..317ea6467d 100644
--- a/base/base.pro
+++ b/base/base.pro
@@ -59,6 +59,7 @@ HEADERS += \
     mru_cache.hpp \
     mutex.hpp \
     object_tracker.hpp \
+    observer_list.hpp \
     pseudo_random.hpp \
     regexp.hpp \
     resource_pool.hpp \
diff --git a/base/base_tests/base_tests.pro b/base/base_tests/base_tests.pro
index b1e8ae8a89..6b2bcb923a 100644
--- a/base/base_tests/base_tests.pro
+++ b/base/base_tests/base_tests.pro
@@ -28,6 +28,7 @@ SOURCES += \
   matrix_test.cpp \
   mem_trie_test.cpp \
   mru_cache_test.cpp \
+  observer_list_test.cpp \
   regexp_test.cpp \
   rolling_hash_test.cpp \
   scheduled_task_test.cpp \
diff --git a/base/base_tests/observer_list_test.cpp b/base/base_tests/observer_list_test.cpp
new file mode 100644
index 0000000000..6e3a4ba48f
--- /dev/null
+++ b/base/base_tests/observer_list_test.cpp
@@ -0,0 +1,68 @@
+#include "../../testing/testing.hpp"
+
+#include "../observer_list.hpp"
+
+#include "../../std/string.hpp"
+
+namespace
+{
+struct Observer
+{
+  Observer() : status(0) {}
+
+  void OnOperationCompleted(string const & message, int status)
+  {
+    this->message = message;
+    this->status = status;
+  }
+
+  string message;
+  int status;
+};
+}  // namespace
+
+UNIT_TEST(ObserverList_Basic)
+{
+  Observer observer0;
+  Observer observer1;
+  Observer observer2;
+
+  my::ObserverList<Observer> observers;
+
+  // Register all observers in a list. Also check that it's not
+  // possible to add the same observer twice.
+  TEST(observers.Add(observer0), ());
+  TEST(!observers.Add(observer0), ());
+
+  TEST(observers.Add(observer1), ());
+  TEST(!observers.Add(observer1), ());
+
+  TEST(observers.Add(observer2), ());
+  TEST(!observers.Add(observer2), ());
+
+  TEST(!observers.Add(observer1), ());
+  TEST(!observers.Add(observer2), ());
+
+  string const message = "HTTP OK";
+  observers.ForEach(&Observer::OnOperationCompleted, message, 204);
+
+  // Check observers internal state.
+  TEST_EQUAL(message, observer0.message, ());
+  TEST_EQUAL(204, observer0.status, ());
+
+  TEST_EQUAL(message, observer1.message, ());
+  TEST_EQUAL(204, observer1.status, ());
+
+  TEST_EQUAL(message, observer2.message, ());
+  TEST_EQUAL(204, observer2.status, ());
+
+  // Remove all observers from a list.
+  TEST(observers.Remove(observer0), ());
+  TEST(!observers.Remove(observer0), ());
+
+  TEST(observers.Remove(observer1), ());
+  TEST(!observers.Remove(observer1), ());
+
+  TEST(observers.Remove(observer2), ());
+  TEST(!observers.Remove(observer2), ());
+}
diff --git a/base/observer_list.hpp b/base/observer_list.hpp
new file mode 100644
index 0000000000..915c78f1d8
--- /dev/null
+++ b/base/observer_list.hpp
@@ -0,0 +1,47 @@
+#pragma once
+
+#include "../std/algorithm.hpp"
+#include "../std/mutex.hpp"
+#include "../std/vector.hpp"
+
+namespace my
+{
+/// This class represents a thread-safe observers list.  It allows to
+/// add/remove observers as well as trigger them all.
+template <typename TObserver>
+class ObserverList
+{
+public:
+  bool Add(TObserver & observer)
+  {
+    lock_guard<mutex> lock(m_observersLock);
+    auto it = find(m_observers.begin(), m_observers.end(), &observer);
+    if (it != m_observers.end())
+      return false;
+    m_observers.push_back(&observer);
+    return true;
+  }
+
+  bool Remove(TObserver & observer)
+  {
+    lock_guard<mutex> lock(m_observersLock);
+    auto it = find(m_observers.begin(), m_observers.end(), &observer);
+    if (it == m_observers.end())
+      return false;
+    m_observers.erase(it);
+    return true;
+  }
+
+  template <typename F, typename... Args>
+  void ForEach(F fn, Args const &... args)
+  {
+    lock_guard<mutex> lock(m_observersLock);
+    for (TObserver * observer : m_observers)
+      (observer->*fn)(args...);
+  }
+
+private:
+  vector<TObserver *> m_observers;
+  mutex m_observersLock;
+};
+}  // namespace my