Pepper: Introduce ThreadAwareCallback.

ppapi/shared_impl/thread_aware_callback.h

+// Copyright (c) 2013 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.
+
+#ifndef PPAPI_SHARED_IMPL_THREAD_AWARE_CALLBACK_H_
+#define PPAPI_SHARED_IMPL_THREAD_AWARE_CALLBACK_H_
+
+#include "base/basictypes.h"
+#include "base/bind.h"
+#include "base/memory/ref_counted.h"
+#include "ppapi/shared_impl/ppapi_shared_export.h"
+#include "ppapi/shared_impl/proxy_lock.h"
+
+namespace ppapi {
+
+class MessageLoopShared;
+
+namespace internal {
+
+class PPAPI_SHARED_EXPORT ThreadAwareCallbackBase {
+ protected:
+  ThreadAwareCallbackBase();
+  ~ThreadAwareCallbackBase();
+
+  static bool HasTargetLoop();
+
+  void InternalRunOnTargetThread(const base::Closure& closure);
+
+ private:
+  class Core;
+
+  scoped_refptr<MessageLoopShared> target_loop_;
+  scoped_refptr<Core> core_;
+
+  DISALLOW_COPY_AND_ASSIGN(ThreadAwareCallbackBase);
+};
+
+}  // namespace internal
+
+// Some PPB interfaces have methods that set a custom callback. Usually, the
+// callback has to be called on the same thread as the one it was set on.
+// ThreadAwareCallback keeps track of the target thread, and posts a task to run
+// on it if requested from a different thread.
+//
+// Please note that:
+// - Unlike TrackedCallback, there is no restriction on how many times the
+//   callback will be called.
+// - When a ThreadAwareCallback object is destroyed, all pending tasks to run
+//   the callback will be ignored. It is designed this way so that when the
+//   resource is destroyed or the callback is cancelled by the plugin, we can
+//   simply delete the ThreadAwareCallback object to prevent touching the
+//   callback later.
+// - When RunOnTargetThread() is called on the target thread, the callback runs
+//   immediately.
+template <class FuncType>
+class ThreadAwareCallback : public internal::ThreadAwareCallbackBase {
+ public:
+  // The caller takes ownership of the returned object.
+  // NULL is returned if the current thread doesn't have an associated Pepper
+  // message loop, or |func| is NULL.
+  static ThreadAwareCallback* Create(FuncType func) {
+    if (!func || !HasTargetLoop())
+      return NULL;
+    return new ThreadAwareCallback(func);
+  }
+
+  ~ThreadAwareCallback() {
+  }
+
+  void RunOnTargetThread() {
+    InternalRunOnTargetThread(base::Bind(func_));
+  }
+
+  template <class P1>
+  void RunOnTargetThread(const P1& p1) {
+    InternalRunOnTargetThread(base::Bind(func_, p1));
+  }
+
+  template <class P1, class P2>
+  void RunOnTargetThread(const P1& p1, const P2& p2) {
+    InternalRunOnTargetThread(base::Bind(func_, p1, p2));
+  }
+
+  template <class P1, class P2, class P3>
+  void RunOnTargetThread(const P1& p1, const P2& p2, const P3& p3) {
+    InternalRunOnTargetThread(base::Bind(func_, p1, p2, p3));
+  }
+
+  template <class P1, class P2, class P3, class P4>
+  void RunOnTargetThread(const P1& p1,
+                         const P2& p2,
+                         const P3& p3,
+                         const P4& p4) {
+    InternalRunOnTargetThread(base::Bind(func_, p1, p2, p3, p4));
+  }
+
+  template <class P1, class P2, class P3, class P4, class P5>
+  void RunOnTargetThread(const P1& p1,
+                         const P2& p2,
+                         const P3& p3,
+                         const P4& p4,
+                         const P5& p5) {
+    InternalRunOnTargetThread(base::Bind(func_, p1, p2, p3, p4, p5));
+  }
+
+ private:
+  explicit ThreadAwareCallback(FuncType func) : func_(func) {
+  }
+
+  FuncType func_;
+};
+
+}  // namespace ppapi
+
+#endif  // PPAPI_SHARED_IMPL_THREAD_AWARE_CALLBACK_H_