Move PostTaskAndReplyWithStatus into task_runner_helpers.h

base/task_runner.h

Index: base/task_runner.h
diff --git a/base/task_runner.h b/base/task_runner.h
index 894eb878f603d5fa5fe7030704374b5899533221..61b7aaee491fb90dfcfc07b52d7dea83e09f78de 100644
--- a/base/task_runner.h
+++ b/base/task_runner.h
@@ -8,7 +8,10 @@
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
-#include "base/callback_forward.h"
+#include "base/bind.h"

[willchan no longer on Chromium, 2012/04/04 17:35:49]

I have a problem with all these new headers. I see why you added them, but
TaskRunner is used very very widely in chrome code, due to MessageLoop
inheriting from it. That means we should be careful about what we include. I'm
torn, but sorta leaning towards moving this into a utility header and making it
a non-member function that takes a TaskRunner as a parameter, rather than being
a member function of TaskRunner.

I'd love to hear thoughts on this.

[battre, 2012/04/04 19:47:41]

Either way is fine with me. I'll follow your decision.

[willchan no longer on Chromium, 2012/04/05 16:53:03]

darin/akalin, feel free to chime in, but otherwise I'm going to ask for a
task_runner_util.h. I figure that in the future, we may have more of these
helpers anyway, so I'd like to defer to a helper file and reduce #includes for
the common case.

battre: please give them another day, and if there's no NACK, proceed.

[battre, 2012/04/12 06:46:33]

Done.

+#include "base/bind_helpers.h"
+#include "base/callback.h"
+#include "base/logging.h"
 #include "base/memory/ref_counted.h"
 #include "base/time.h"
 
@@ -18,6 +21,41 @@ class Location;
 
 namespace base {
 
+namespace internal {
+
+// Helper class for TaskRunner::PostTaskAndReplyWithResult.
+template <typename ReturnType>
+void ReturnAsParamAdapter(const Callback<ReturnType(void)>& func,
+                          ReturnType* result) {
+  if (!func.is_null())
+    *result = func.Run();
+}
+
+// Helper class for TaskRunner::PostTaskAndReplyWithResult.
+template <typename ReturnType>
+Closure ReturnAsParam(const Callback<ReturnType(void)>& func,
+                      ReturnType* result) {
+  DCHECK(result);
+  return Bind(&ReturnAsParamAdapter<ReturnType>, func, result);
+}
+
+// Helper class for TaskRunner::PostTaskAndReplyWithResult.
+template <typename ReturnType>
+void ReplyAdapter(const Callback<void(ReturnType)>& callback,
+                  ReturnType* result) {
+  DCHECK(result);
+  if(!callback.is_null())
+    callback.Run(*result);
+}
+
+// Helper class for TaskRunner::PostTaskAndReplyWithResult.
+template <typename ReturnType, typename OWNED>

[willchan no longer on Chromium, 2012/04/04 17:35:49]

s/OWNED/OwnedType/

[battre, 2012/04/12 06:46:33]

Done.

+Closure ReplyHelper(const Callback<void(ReturnType)>& callback, OWNED result) {
+  return Bind(&ReplyAdapter<ReturnType>, callback, result);
+}
+
+}  // namespace internal
+
 struct TaskRunnerTraits;
 
 // A TaskRunner is an object that runs posted tasks (in the form of
@@ -134,6 +172,31 @@ class BASE_EXPORT TaskRunner
                         const Closure& task,
                         const Closure& reply);
 
+  // When you have these methods
+  //
+  //   R DoWorkAndReturn();
+  //   void Callback(const R& result);
+  //
+  // and want to call them in a PostTaskAndReply kind of fashion where the
+  // result of DoWorkAndReturn is passed to the Callback, you can use
+  // PostTaskAndReplyWithResult as in this example:
+  //
+  // target_thread_.message_loop_proxy()->PostTaskAndReplyWithResult(
+  //     FROM_HERE,
+  //     Bind(&DoWorkAndReturn),
+  //     Bind(&Callback));
+  template <typename ReturnType>
+  bool PostTaskAndReplyWithResult(
+      const tracked_objects::Location& from_here,
+      const Callback<ReturnType(void)>& task,
+      const Callback<void(ReturnType)>& reply) {
+    ReturnType* result = new ReturnType;
+    return PostTaskAndReply(
+        from_here,
+        internal::ReturnAsParam<ReturnType>(task, result),
+        internal::ReplyHelper(reply, Owned(result)));
+  }
+
  protected:
   friend struct TaskRunnerTraits;