1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef PPAPI_SHARED_IMPL_TRACKED_CALLBACK_H_ 6 #define PPAPI_SHARED_IMPL_TRACKED_CALLBACK_H_ 7 8 #include <map> 9 #include <set> 10 11 #include "base/basictypes.h" 12 #include "base/callback.h" 13 #include "base/memory/ref_counted.h" 14 #include "base/memory/scoped_ptr.h" 15 #include "base/synchronization/condition_variable.h" 16 #include "ppapi/c/pp_completion_callback.h" 17 #include "ppapi/c/pp_instance.h" 18 #include "ppapi/c/pp_resource.h" 19 #include "ppapi/shared_impl/ppapi_shared_export.h" 20 #include "ppapi/shared_impl/ppb_message_loop_shared.h" 21 22 namespace ppapi { 23 24 class CallbackTracker; 25 class MessageLoopShared; 26 class Resource; 27 28 namespace thunk { 29 namespace subtle { 30 // For a friend declaration below. 31 class EnterBase; 32 } 33 } 34 35 // |TrackedCallback| represents a tracked Pepper callback (from the browser to 36 // the plugin), typically still pending. Such callbacks have the standard Pepper 37 // callback semantics. Execution (i.e., completion) of callbacks happens through 38 // objects of subclasses of |TrackedCallback|. Two things are ensured: (1) that 39 // the callback is executed at most once, and (2) once a callback is marked to 40 // be aborted, any subsequent completion is abortive (even if a non-abortive 41 // completion had previously been scheduled). 42 // 43 // The details of non-abortive completion depend on the type of callback (e.g., 44 // different parameters may be required), but basic abort functionality is core. 45 // The ability to post aborts is needed in many situations to ensure that the 46 // plugin is not re-entered into. (Note that posting a task to just run 47 // |Abort()| is different and not correct; calling |PostAbort()| additionally 48 // guarantees that all subsequent completions will be abortive.) 49 // 50 // This class is reference counted so that different things can hang on to it, 51 // and not worry too much about ensuring Pepper callback semantics. Note that 52 // the "owning" |CallbackTracker| will keep a reference until the callback is 53 // completed. 54 // 55 // Subclasses must do several things: 56 // - They must ensure that the callback is executed at most once (by looking at 57 // |completed()| before running the callback). 58 // - They must ensure that the callback is run abortively if it is marked as to 59 // be aborted (by looking at |aborted()| before running the callback). 60 // - They must call |MarkAsCompleted()| immediately before actually running the 61 // callback; see the comment for |MarkAsCompleted()| for a caveat. 62 class PPAPI_SHARED_EXPORT TrackedCallback 63 : public base::RefCountedThreadSafe<TrackedCallback> { 64 public: 65 // Create a tracked completion callback and register it with the tracker. The 66 // resource pointer is not stored. If |resource| is NULL, this callback will 67 // not be added to the callback tracker. 68 TrackedCallback(Resource* resource, const PP_CompletionCallback& callback); 69 70 // These run the callback in an abortive manner, or post a task to do so (but 71 // immediately marking the callback as to be aborted). 72 void Abort(); 73 void PostAbort(); 74 75 // Run the callback with the given result. If the callback had previously been 76 // marked as to be aborted (by |PostAbort()|), |result| will be ignored and 77 // the callback will be run with result |PP_ERROR_ABORTED|. 78 // 79 // Run() will invoke the call immediately, if invoked from the target thread 80 // (as determined by target_loop_). If invoked on a different thread, the 81 // callback will be scheduled to run later on target_loop_. 82 void Run(int32_t result); 83 // PostRun is like Run(), except it guarantees that the callback will be run 84 // later. In particular, if you invoke PostRun on the same thread on which the 85 // callback is targeted to run, it will *not* be run immediately. 86 void PostRun(int32_t result); 87 88 // A task to perform cleanup or write output parameters before the callback 89 // returns a result to the plugin. The |result| parameter has the result so 90 // far, e.g. whether the callback has been aborted. If the callback hasn't 91 // been aborted the return value of the task will become the callback result. 92 // The task is always called on the same thread as the callback to the plugin. 93 typedef base::Callback<int32_t(int32_t /* result */)> CompletionTask; 94 95 // Sets a task that is run just before calling back into the plugin. This 96 // should only be called once. 97 void set_completion_task(const CompletionTask& completion_task); 98 99 // Returns the ID of the resource which "owns" the callback, or 0 if the 100 // callback is not associated with any resource. resource_id()101 PP_Resource resource_id() const { return resource_id_; } 102 103 // Returns true if the callback was completed (possibly aborted). completed()104 bool completed() const { return completed_; } 105 106 // Returns true if the callback was or should be aborted; this will be the 107 // case whenever |Abort()| or |PostAbort()| is called before a non-abortive 108 // completion. aborted()109 bool aborted() const { return aborted_; } 110 111 // Returns true if this is a blocking callback. is_blocking()112 bool is_blocking() { return !callback_.func; } 113 target_loop()114 MessageLoopShared* target_loop() const { return target_loop_.get(); } 115 116 // Determines if the given callback is pending. A callback is pending if it 117 // has not completed and has not been aborted. When receiving a plugin call, 118 // use this to detect if |callback| represents an operation in progress. When 119 // finishing a plugin call, use this to determine whether to write 'out' 120 // params and Run |callback|. 121 // NOTE: an aborted callback has not necessarily completed, so a false result 122 // doesn't imply that the callback has completed. 123 // As a convenience, if |callback| is null, this returns false. 124 static bool IsPending(const scoped_refptr<TrackedCallback>& callback); 125 126 // Helper to determine if the given callback is scheduled to run on another 127 // message loop. 128 static bool IsScheduledToRun(const scoped_refptr<TrackedCallback>& callback); 129 130 protected: is_required()131 bool is_required() { 132 return (callback_.func && 133 !(callback_.flags & PP_COMPLETIONCALLBACK_FLAG_OPTIONAL)); 134 } is_optional()135 bool is_optional() { 136 return (callback_.func && 137 (callback_.flags & PP_COMPLETIONCALLBACK_FLAG_OPTIONAL)); 138 } has_null_target_loop()139 bool has_null_target_loop() const { return target_loop_.get() == NULL; } 140 141 private: 142 // TrackedCallback and EnterBase manage dealing with how to invoke callbacks 143 // appropriately. Pepper interface implementations and proxies should not have 144 // to check the type of callback, block, or mark them complete explicitly. 145 friend class ppapi::thunk::subtle::EnterBase; 146 147 // Block until the associated operation has completed. Returns the result. 148 // This must only be called on a non-main thread on a blocking callback. 149 int32_t BlockUntilComplete(); 150 151 // Mark this object as complete and remove it from the tracker. This must only 152 // be called once. Note that running this may result in this object being 153 // deleted (so keep a reference if it'll still be needed). 154 void MarkAsCompleted(); 155 156 // This class is ref counted. 157 friend class base::RefCountedThreadSafe<TrackedCallback>; 158 virtual ~TrackedCallback(); 159 160 // Flag used by |PostAbort()| and |PostRun()| to check that we don't schedule 161 // the callback more than once. 162 bool is_scheduled_; 163 164 scoped_refptr<CallbackTracker> tracker_; 165 PP_Resource resource_id_; 166 bool completed_; 167 bool aborted_; 168 PP_CompletionCallback callback_; 169 170 // Task to run just before calling back into the plugin. 171 CompletionTask completion_task_; 172 173 // The MessageLoopShared on which this callback should be run. This will be 174 // NULL if we're in-process. 175 scoped_refptr<MessageLoopShared> target_loop_; 176 177 int32_t result_for_blocked_callback_; 178 // Used for pausing/waking the blocked thread if this is a blocking completion 179 // callback. Note that in-process, there is no lock, blocking callbacks are 180 // not allowed, and therefore this pointer will be NULL. 181 scoped_ptr<base::ConditionVariable> operation_completed_condvar_; 182 183 DISALLOW_IMPLICIT_CONSTRUCTORS(TrackedCallback); 184 }; 185 186 } // namespace ppapi 187 188 #endif // PPAPI_SHARED_IMPL_TRACKED_CALLBACK_H_ 189