| // 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 <stdint.h> |
| |
| #include <map> |
| #include <set> |
| |
| #include "base/callback.h" |
| #include "base/macros.h" |
| #include "base/memory/ref_counted.h" |
| #include "base/memory/scoped_ptr.h" |
| #include "base/synchronization/condition_variable.h" |
| #include "base/synchronization/lock.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" |
| #include "ppapi/shared_impl/ppb_message_loop_shared.h" |
| |
| namespace ppapi { |
| |
| class CallbackTracker; |
| class MessageLoopShared; |
| 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. |
| // The ability to post aborts is needed in many situations to ensure that the |
| // plugin is not re-entered into. (Note that posting a task to just run |
| // |Abort()| is different and not correct; calling |PostAbort()| additionally |
| // guarantees that all subsequent completions will be abortive.) |
| // |
| // This class is reference counted so that different things can hang on to it, |
| // and not worry too much about ensuring Pepper callback semantics. Note that |
| // the "owning" |CallbackTracker| will keep a reference until the callback is |
| // completed. |
| // |
| // A note on threading: |
| // TrackedCallback is usable on any thread. It is *mostly* only used when |
| // ppapi::ProxyLock is held. However, it's necessary that Run() can be called |
| // without the ProxyLock. This is used to allow running the callback from |
| // the IO thread. In particular, blocking callbacks may not have a message loop |
| // to which we could post, so Run() must be able to signal the condition |
| // variable to wake up the thread that's waiting on the blocking callback, and |
| // Run() must be able to do this while not holding the ProxyLock. |
| 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. 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|. |
| // |
| // Run() will invoke the call immediately, if invoked from the target thread |
| // (as determined by target_loop_). If invoked on a different thread, the |
| // callback will be scheduled to run later on target_loop_. |
| void Run(int32_t result); |
| void AcquireProxyLockAndRun(int32_t result); |
| // PostRun is like Run(), except it guarantees that the callback will be run |
| // later. In particular, if you invoke PostRun on the same thread on which the |
| // callback is targeted to run, it will *not* be run immediately. |
| void PostRun(int32_t result); |
| |
| // A task to perform cleanup or write output parameters before the callback |
| // returns a result to the plugin. The |result| parameter has the result so |
| // far, e.g. whether the callback has been aborted. If the callback hasn't |
| // been aborted the return value of the task will become the callback result. |
| // The task is always called on the same thread as the callback to the plugin. |
| typedef base::Callback<int32_t(int32_t /* result */)> CompletionTask; |
| |
| // Sets a task that is run just before calling back into the plugin. This |
| // should only be called once. Note that the CompletionTask always runs while |
| // holding the ppapi::ProxyLock. |
| void set_completion_task(const CompletionTask& completion_task); |
| |
| // 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 this is a blocking callback. |
| bool is_blocking() const { |
| // This is set on construction and never changes after that, so there is |
| // no need to lock. |
| return !callback_.func; |
| } |
| |
| MessageLoopShared* target_loop() const { |
| // This is set on construction and never changes after that, so there is |
| // no need to lock. |
| return target_loop_.get(); |
| } |
| |
| // Determines if the given callback is pending. A callback is pending if it |
| // has not completed and has not been aborted. When receiving a plugin call, |
| // use this to detect if |callback| represents an operation in progress. When |
| // finishing a plugin call, use this to determine whether to write 'out' |
| // params and Run |callback|. |
| // NOTE: an aborted callback has not necessarily completed, so a false result |
| // doesn't imply that the callback has completed. |
| // As a convenience, if |callback| is null, this returns false. |
| static bool IsPending(const scoped_refptr<TrackedCallback>& callback); |
| |
| // Helper to determine if the given callback is scheduled to run on another |
| // message loop. |
| static bool IsScheduledToRun(const scoped_refptr<TrackedCallback>& callback); |
| |
| private: |
| bool is_required() { |
| return (callback_.func && |
| !(callback_.flags & PP_COMPLETIONCALLBACK_FLAG_OPTIONAL)); |
| } |
| bool has_null_target_loop() const { return target_loop_.get() == NULL; } |
| |
| // Same as PostRun(), but lock_ must already be held. |
| void PostRunWithLock(int32_t result); |
| |
| void SignalBlockingCallback(int32_t result); |
| |
| // TrackedCallback and EnterBase work together to provide appropriate behavior |
| // for callbacks. Pepper interface implementations and proxies should |
| // usually not have to check whether callbacks are required, optional, or |
| // blocking. Nor should interface and proxy implementations have to worry |
| // about blocking on a callback or marking them complete explicitly. |
| // |
| // (There are exceptions; e.g. FileIO checks is_blocking() in order to do |
| // some operations directly on the calling thread if possible.) |
| 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(); |
| void MarkAsCompletedWithLock(); |
| |
| // This class is ref counted. |
| friend class base::RefCountedThreadSafe<TrackedCallback>; |
| ~TrackedCallback(); |
| |
| mutable base::Lock lock_; |
| |
| // Flag used by |PostAbort()| and |PostRun()| to check that we don't schedule |
| // the callback more than once. |
| bool is_scheduled_; |
| |
| scoped_refptr<CallbackTracker> tracker_; |
| PP_Resource resource_id_; |
| bool completed_; |
| bool aborted_; |
| PP_CompletionCallback callback_; |
| |
| // Task to run just before calling back into the plugin. |
| CompletionTask completion_task_; |
| |
| // The MessageLoopShared on which this callback should be run. This will be |
| // NULL if we're in-process. |
| scoped_refptr<MessageLoopShared> target_loop_; |
| |
| 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_ |