PPAPI: Make blocking completion callbacks work.

ppapi/shared_impl/tracked_callback.h

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 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_TRACKED_CALLBACK_H_
 #define PPAPI_SHARED_IMPL_TRACKED_CALLBACK_H_
 
 #include <map>
 #include <set>
 
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
+#include "base/synchronization/condition_variable.h"
 #include "ppapi/c/pp_completion_callback.h"
+#include "ppapi/c/pp_instance.h"
 #include "ppapi/c/pp_resource.h"
 #include "ppapi/shared_impl/ppapi_shared_export.h"
 
 namespace ppapi {
 
 class CallbackTracker;
 class Resource;
 
+namespace thunk {
+namespace subtle {
+// For a friend declaration below.
+class EnterBase;
+}
+}
+
 // |TrackedCallback| represents a tracked Pepper callback (from the browser to
 // the plugin), typically still pending. Such callbacks have the standard Pepper
 // callback semantics. Execution (i.e., completion) of callbacks happens through
 // objects of subclasses of |TrackedCallback|. Two things are ensured: (1) that
 // the callback is executed at most once, and (2) once a callback is marked to
 // be aborted, any subsequent completion is abortive (even if a non-abortive
 // completion had previously been scheduled).
 //
 // The details of non-abortive completion depend on the type of callback (e.g.,
 // different parameters may be required), but basic abort functionality is core.
@@ skipping 11 matching lines @@
 //  - They must ensure that the callback is executed at most once (by looking at
 //    |completed()| before running the callback).
 //  - They must ensure that the callback is run abortively if it is marked as to
 //    be aborted (by looking at |aborted()| before running the callback).
 //  - They must call |MarkAsCompleted()| immediately before actually running the
 //    callback; see the comment for |MarkAsCompleted()| for a caveat.
 class PPAPI_SHARED_EXPORT TrackedCallback
     : public base::RefCountedThreadSafe<TrackedCallback> {
  public:
   // Create a tracked completion callback and register it with the tracker. The
-  // resource pointer is not stored.
-  TrackedCallback(Resource* resource,
-                  const PP_CompletionCallback& callback);
+  // resource pointer is not stored. If |resource| is NULL, this callback will
+  // not be added to the callback tracker.
+  TrackedCallback(Resource* resource, const PP_CompletionCallback& callback);
 
   // These run the callback in an abortive manner, or post a task to do so (but
   // immediately marking the callback as to be aborted).
   void Abort();
   void PostAbort();
 
   // Run the callback with the given result. If the callback had previously been
   // marked as to be aborted (by |PostAbort()|), |result| will be ignored and
   // the callback will be run with result |PP_ERROR_ABORTED|.
   //
   // See also ClearAndRun().
   void Run(int32_t result);
+  void PostRun(int32_t result);
+
+  void BlockUntilRun();
 
   // Returns the ID of the resource which "owns" the callback, or 0 if the
   // callback is not associated with any resource.
   PP_Resource resource_id() const { return resource_id_; }
 
   // Returns true if the callback was completed (possibly aborted).
   bool completed() const { return completed_; }
 
   // Returns true if the callback was or should be aborted; this will be the
   // case whenever |Abort()| or |PostAbort()| is called before a non-abortive
   // completion.
   bool aborted() const { return aborted_; }
 
   // Helper to determine if the given callback is set and not yet completed.
   // The normal pattern is to use a scoped_refptr to hold a callback. This
   // function tells you if the operation is currently in progress by checking
   // both the null-ness of the scoped_refptr, as well as the completion state
   // of the callback (which may still be out-standing via a PostAbort).
   static bool IsPending(const scoped_refptr<TrackedCallback>& callback);
 
   // Runs the given callback, clearing the given scoped_refptr before execution.
   // This is useful for cases where there can be only one pending callback, and
-  // the presence of the callback indicates is one is pending. Such code would
+  // the presence of the callback indicates one is pending. Such code would
   // normally want to clear it before execution so the plugin can issue a new
   // request.
   static void ClearAndRun(scoped_refptr<TrackedCallback>* callback,
                           int32_t result);
 
   // Same as ClearAndRun except it calls Abort().
   static void ClearAndAbort(scoped_refptr<TrackedCallback>* callback);
 
+ protected:
+  bool is_blocking() {
+    return !callback_.func;
+  }
+  bool is_required() {
+    return (callback_.func &&
+            !(callback_.flags & PP_COMPLETIONCALLBACK_FLAG_OPTIONAL));
+  }
+  bool is_optional() {
+    return (callback_.func &&
+            (callback_.flags & PP_COMPLETIONCALLBACK_FLAG_OPTIONAL));
+  }
+
  private:
-  // This class is ref counted.
-  friend class base::RefCountedThreadSafe<TrackedCallback>;
-  virtual ~TrackedCallback();
+  // TrackedCallback and EnterBase manage dealing with how to invoke callbacks
+  // appropriately. Pepper interface implementations and proxies should not have
+  // to check the type of callback, block, or mark them complete explicitly.
+  friend class ppapi::thunk::subtle::EnterBase;
+
+  // Block until the associated operation has completed. Returns the result.
+  // This must only be called on a non-main thread on a blocking callback.
+  int32_t BlockUntilComplete();
 
   // Mark this object as complete and remove it from the tracker. This must only
   // be called once. Note that running this may result in this object being
   // deleted (so keep a reference if it'll still be needed).
   void MarkAsCompleted();
 
-  // Factory used by |PostAbort()|. Note that it's safe to cancel any pending
-  // posted aborts on destruction -- before it's destroyed, the "owning"
-  // |CallbackTracker| must have gone through and done (synchronous) |Abort()|s.
-  base::WeakPtrFactory<TrackedCallback> abort_impl_factory_;
+  // This class is ref counted.
+  friend class base::RefCountedThreadSafe<TrackedCallback>;
+  virtual ~TrackedCallback();
+
+  // Factory used by |PostAbort()| and |PostRun()|. Note that it's safe to
+  // cancel any pending posted tasks on destruction -- before it's destroyed,
+  // the "owning" |CallbackTracker| must have gone through and done
+  // (synchronous) |Abort()|s.
+  base::WeakPtrFactory<TrackedCallback> weak_ptr_factory_;
 
   scoped_refptr<CallbackTracker> tracker_;
   PP_Resource resource_id_;
   bool completed_;
   bool aborted_;
   PP_CompletionCallback callback_;
 
+  int32_t result_for_blocked_callback_;
+  // Used for pausing/waking the blocked thread if this is a blocking completion
+  // callback. Note that in-process, there is no lock, blocking callbacks are
+  // not allowed, and therefore this pointer will be NULL.
+  scoped_ptr<base::ConditionVariable> operation_completed_condvar_;
+
   DISALLOW_IMPLICIT_CONSTRUCTORS(TrackedCallback);
 };
 
 }  // namespace ppapi
 
 #endif  // PPAPI_SHARED_IMPL_TRACKED_CALLBACK_H_