Fixing CancelableCallback to use variadic templates. Previously, 2-argument callbacks wouldn't compile.

Review URL: https://codereview.chromium.org/694193003

Cr-Commit-Position: refs/heads/master@{#304360}

1 files changed, 13 insertions, 150 deletions

diff --git a/base/cancelable_callback.h b/base/cancelable_callback.h
index 159100f..91eb046 100644
--- a/base/cancelable_callback.h
+++ b/base/cancelable_callback.h
@@ -55,13 +55,13 @@ namespace base {
 template <typename Sig>
 class CancelableCallback;
 
-template <>
-class CancelableCallback<void(void)> {
+template <typename... A>
+class CancelableCallback<void(A...)> {
  public:
   CancelableCallback() : weak_factory_(this) {}
 
   // |callback| must not be null.
-  explicit CancelableCallback(const base::Callback<void(void)>& callback)
+  explicit CancelableCallback(const base::Callback<void(A...)>& callback)
       : weak_factory_(this),
         callback_(callback) {
     DCHECK(!callback.is_null());
@@ -84,7 +84,7 @@ class CancelableCallback<void(void)> {
 
   // Sets |callback| as the closure that may be cancelled. |callback| may not
   // be null. Outstanding and any previously wrapped callbacks are cancelled.
-  void Reset(const base::Callback<void(void)>& callback) {
+  void Reset(const base::Callback<void(A...)>& callback) {
     DCHECK(!callback.is_null());
 
     // Outstanding tasks (e.g., posted to a message loop) must not be called.
@@ -97,173 +97,36 @@ class CancelableCallback<void(void)> {
   }
 
   // Returns a callback that can be disabled by calling Cancel().
-  const base::Callback<void(void)>& callback() const {
+  const base::Callback<void(A...)>& callback() const {
     return forwarder_;
   }
 
  private:
-  void Forward() {
-    callback_.Run();
+  void Forward(A... args) const {
+    callback_.Run(args...);
   }
 
   // Helper method to bind |forwarder_| using a weak pointer from
   // |weak_factory_|.
   void InitializeForwarder() {
-    forwarder_ = base::Bind(&CancelableCallback<void(void)>::Forward,
+    forwarder_ = base::Bind(&CancelableCallback<void(A...)>::Forward,
                             weak_factory_.GetWeakPtr());
   }
 
   // Used to ensure Forward() is not run when this object is destroyed.
-  base::WeakPtrFactory<CancelableCallback<void(void)> > weak_factory_;
+  // TODO(ckehoe): This should be the last class member.
+  // Move it there when crbug.com/433583 is fixed.
+  base::WeakPtrFactory<CancelableCallback<void(A...)> > weak_factory_;
 
   // The wrapper closure.
-  base::Callback<void(void)> forwarder_;
+  base::Callback<void(A...)> forwarder_;
 
   // The stored closure that may be cancelled.
-  base::Callback<void(void)> callback_;
+  base::Callback<void(A...)> callback_;
 
   DISALLOW_COPY_AND_ASSIGN(CancelableCallback);
 };
 
-template <typename A1>
-class CancelableCallback<void(A1)> {
- public:
-  CancelableCallback() : weak_factory_(this) {}
-
-  // |callback| must not be null.
-  explicit CancelableCallback(const base::Callback<void(A1)>& callback)
-      : weak_factory_(this),
-        callback_(callback) {
-    DCHECK(!callback.is_null());
-    InitializeForwarder();
-  }
-
-  ~CancelableCallback() {}
-
-  // Cancels and drops the reference to the wrapped callback.
-  void Cancel() {
-    weak_factory_.InvalidateWeakPtrs();
-    forwarder_.Reset();
-    callback_.Reset();
-  }
-
-  // Returns true if the wrapped callback has been cancelled.
-  bool IsCancelled() const {
-    return callback_.is_null();
-  }
-
-  // Sets |callback| as the closure that may be cancelled. |callback| may not
-  // be null. Outstanding and any previously wrapped callbacks are cancelled.
-  void Reset(const base::Callback<void(A1)>& callback) {
-    DCHECK(!callback.is_null());
-
-    // Outstanding tasks (e.g., posted to a message loop) must not be called.
-    Cancel();
-
-    // |forwarder_| is no longer valid after Cancel(), so re-bind.
-    InitializeForwarder();
-
-    callback_ = callback;
-  }
-
-  // Returns a callback that can be disabled by calling Cancel().
-  const base::Callback<void(A1)>& callback() const {
-    return forwarder_;
-  }
-
- private:
-  void Forward(A1 a1) const {
-    callback_.Run(a1);
-  }
-
-  // Helper method to bind |forwarder_| using a weak pointer from
-  // |weak_factory_|.
-  void InitializeForwarder() {
-    forwarder_ = base::Bind(&CancelableCallback<void(A1)>::Forward,
-                            weak_factory_.GetWeakPtr());
-  }
-
-  // Used to ensure Forward() is not run when this object is destroyed.
-  base::WeakPtrFactory<CancelableCallback<void(A1)> > weak_factory_;
-
-  // The wrapper closure.
-  base::Callback<void(A1)> forwarder_;
-
-  // The stored closure that may be cancelled.
-  base::Callback<void(A1)> callback_;
-
-  DISALLOW_COPY_AND_ASSIGN(CancelableCallback);
-};
-
-template <typename A1, typename A2>
-class CancelableCallback<void(A1, A2)> {
- public:
-  CancelableCallback() : weak_factory_(this) {}
-
-  // |callback| must not be null.
-  explicit CancelableCallback(const base::Callback<void(A1, A2)>& callback)
-      : weak_factory_(this),
-        callback_(callback) {
-    DCHECK(!callback.is_null());
-    InitializeForwarder();
-  }
-
-  ~CancelableCallback() {}
-
-  // Cancels and drops the reference to the wrapped callback.
-  void Cancel() {
-    weak_factory_.InvalidateWeakPtrs();
-    forwarder_.Reset();
-    callback_.Reset();
-  }
-
-  // Returns true if the wrapped callback has been cancelled.
-  bool IsCancelled() const {
-    return callback_.is_null();
-  }
-
-  // Sets |callback| as the closure that may be cancelled. |callback| may not
-  // be null. Outstanding and any previously wrapped callbacks are cancelled.
-  void Reset(const base::Callback<void(A1, A2)>& callback) {
-    DCHECK(!callback.is_null());
-
-    // Outstanding tasks (e.g., posted to a message loop) must not be called.
-    Cancel();
-
-    // |forwarder_| is no longer valid after Cancel(), so re-bind.
-    InitializeForwarder();
-
-    callback_ = callback;
-  }
-
-  // Returns a callback that can be disabled by calling Cancel().
-  const base::Callback<void(A1, A2)>& callback() const {
-    return forwarder_;
-  }
-
- private:
-  void Forward(A1 a1, A2 a2) const {
-    callback_.Run(a1, a2);
-  }
-
-  // Helper method to bind |forwarder_| using a weak pointer from
-  // |weak_factory_|.
-  void InitializeForwarder() {
-    forwarder_ = base::Bind(&CancelableCallback<void(A1, A2)>::Forward,
-                            weak_factory_.GetWeakPtr());
-  }
-
-  // The wrapper closure.
-  base::Callback<void(A1, A2)> forwarder_;
-
-  // The stored closure that may be cancelled.
-  base::Callback<void(A1, A2)> callback_;
-
-  // Used to ensure Forward() is not run when this object is destroyed.
-  base::WeakPtrFactory<CancelableCallback<void(A1, A2)> > weak_factory_;
-  DISALLOW_COPY_AND_ASSIGN(CancelableCallback);
-};
-
 typedef CancelableCallback<void(void)> CancelableClosure;
 
 }  // namespace base