Refactor FFmpegVideoDecoder to try and generalize code common to all video decoders.

media/base/mock_task.h

+// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// This file provides some utility classes that help with testing APIs which use
+// callbacks.
+//
+// -- InvokeRunnable --
+// The InvokeRunnable is an action that can be used a gMock mock object to
+// invoke the Run() method on mock argument.  Example:
+//
+//   class MockFoo : public Foo {
+//    public:
+//     MOCK_METHOD0(DoSomething, void(Task* done_cb));
+//   };
+//
+//   EXPECT_CALL(foo, DoSomething(_)).WillOnce(WithArg<0>(InvokeRunnable()));
+//
+// Then you pass "foo" to something that will eventually call DoSomething().
+// The mock action will ensure that passed in done_cb is invoked.
+//
+//
+// -- TaskMocker --
+// The TaskMocker class lets you create mock callbacks.  Callbacks are
+// difficult to mock because ownership of the callback object is often passed
+// to the funciton being invoked.  TaskMocker solves this by providing a
+// GetTask() function that creates a new, single-use task that delegates to
+// the originating TaskMocker object.  Expectations are placed on the
+// originating TaskMocker object.  Each callback retrieved by GetTask() is
+// tracked to ensure that it is properly deleted.  The TaskMocker expects to
+// outlive all the callbacks retrieved by GetTask().
+//
+// Example:
+//
+//   TaskMocker done_cb;
+//   EXPECT_CALL(done_cb, Run()).Times(3);
+//
+//   func1(done_cb.GetTask());
+//   func2(done_cb.GetTask());
+//   func3(done_cb.GetTask());
+//
+//   // All 3 callbacks from GetTask() should be deleted before done_cb goes out
+//   // of scope.
+//
+// This class is not threadsafe.
+//
+// TODO(ajwong): Is it even worth bothering with gmock here?
+// TODO(ajwong): Move MockFilterCallback here and merge the implementation
+// differences.
+
+#ifndef MEDIA_BASE_MOCK_TASK_H_
+#define MEDIA_BASE_MOCK_TASK_H_
+
+#include "base/task.h"
+#include "testing/gmock/include/gmock/gmock.h"
+
+namespace media {
+
+ACTION(InvokeRunnable) {
+  arg0->Run();
+  delete arg0;
+}
+
+class TaskMocker {
+ public:
+  TaskMocker()
+      : outstanding_tasks_(0) {
+  }
+  ~TaskMocker() {
+    CHECK(outstanding_tasks_ == 0)
+        << "If outstanding_tasks_ is not zero, tasks have been leaked.";
+  }
+
+  Task* CreateTask() {
+    return new CountingTask(this);
+  }
+
+  MOCK_METHOD0(Run, void());
+
+ private:
+  friend class CountingTask;
+  class CountingTask : public Task {
+   public:
+    CountingTask(TaskMocker* origin)
+        : origin_(origin) {
+      origin_->outstanding_tasks_++;
+    }
+
+    virtual void Run() {
+      origin_->Run();
+    }
+
+    virtual ~CountingTask() {
+      origin_->outstanding_tasks_--;
+    }
+
+   private:
+    TaskMocker* origin_;
+
+    DISALLOW_COPY_AND_ASSIGN(CountingTask);
+  };
+
+  int outstanding_tasks_;
+
+  DISALLOW_COPY_AND_ASSIGN(TaskMocker);
+};
+
+}  // namespace media
+
+#endif  //MEDIA_BASE_MOCK_TASK_H_