tracked_callback.h revision 5821806d5e7f356e8fa4b058a389a808ea183019
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/memory/ref_counted.h" 13#include "base/memory/scoped_ptr.h" 14#include "base/synchronization/condition_variable.h" 15#include "ppapi/c/pp_completion_callback.h" 16#include "ppapi/c/pp_instance.h" 17#include "ppapi/c/pp_resource.h" 18#include "ppapi/shared_impl/ppapi_shared_export.h" 19#include "ppapi/shared_impl/ppb_message_loop_shared.h" 20 21namespace ppapi { 22 23class CallbackTracker; 24class MessageLoopShared; 25class Resource; 26 27namespace thunk { 28namespace subtle { 29// For a friend declaration below. 30class EnterBase; 31} 32} 33 34// |TrackedCallback| represents a tracked Pepper callback (from the browser to 35// the plugin), typically still pending. Such callbacks have the standard Pepper 36// callback semantics. Execution (i.e., completion) of callbacks happens through 37// objects of subclasses of |TrackedCallback|. Two things are ensured: (1) that 38// the callback is executed at most once, and (2) once a callback is marked to 39// be aborted, any subsequent completion is abortive (even if a non-abortive 40// completion had previously been scheduled). 41// 42// The details of non-abortive completion depend on the type of callback (e.g., 43// different parameters may be required), but basic abort functionality is core. 44// The ability to post aborts is needed in many situations to ensure that the 45// plugin is not re-entered into. (Note that posting a task to just run 46// |Abort()| is different and not correct; calling |PostAbort()| additionally 47// guarantees that all subsequent completions will be abortive.) 48// 49// This class is reference counted so that different things can hang on to it, 50// and not worry too much about ensuring Pepper callback semantics. Note that 51// the "owning" |CallbackTracker| will keep a reference until the callback is 52// completed. 53// 54// Subclasses must do several things: 55// - They must ensure that the callback is executed at most once (by looking at 56// |completed()| before running the callback). 57// - They must ensure that the callback is run abortively if it is marked as to 58// be aborted (by looking at |aborted()| before running the callback). 59// - They must call |MarkAsCompleted()| immediately before actually running the 60// callback; see the comment for |MarkAsCompleted()| for a caveat. 61class PPAPI_SHARED_EXPORT TrackedCallback 62 : public base::RefCountedThreadSafe<TrackedCallback> { 63 public: 64 // Create a tracked completion callback and register it with the tracker. The 65 // resource pointer is not stored. If |resource| is NULL, this callback will 66 // not be added to the callback tracker. 67 TrackedCallback(Resource* resource, const PP_CompletionCallback& callback); 68 69 // These run the callback in an abortive manner, or post a task to do so (but 70 // immediately marking the callback as to be aborted). 71 void Abort(); 72 void PostAbort(); 73 74 // Run the callback with the given result. If the callback had previously been 75 // marked as to be aborted (by |PostAbort()|), |result| will be ignored and 76 // the callback will be run with result |PP_ERROR_ABORTED|. 77 // 78 // Run() will invoke the call immediately, if invoked from the target thread 79 // (as determined by target_loop_). If invoked on a different thread, the 80 // callback will be scheduled to run later on target_loop_. 81 void Run(int32_t result); 82 // PostRun is like Run(), except it guarantees that the callback will be run 83 // later. In particular, if you invoke PostRun on the same thread on which the 84 // callback is targeted to run, it will *not* be run immediately. 85 void PostRun(int32_t result); 86 87 void BlockUntilRun(); 88 89 // Returns the ID of the resource which "owns" the callback, or 0 if the 90 // callback is not associated with any resource. 91 PP_Resource resource_id() const { return resource_id_; } 92 93 // Returns true if the callback was completed (possibly aborted). 94 bool completed() const { return completed_; } 95 96 // Returns true if the callback was or should be aborted; this will be the 97 // case whenever |Abort()| or |PostAbort()| is called before a non-abortive 98 // completion. 99 bool aborted() const { return aborted_; } 100 101 // Helper to determine if the given callback is set and not yet completed. 102 // The normal pattern is to use a scoped_refptr to hold a callback. This 103 // function tells you if the operation is currently in progress by checking 104 // both the null-ness of the scoped_refptr, as well as the completion state 105 // of the callback (which may still be out-standing via a PostAbort). 106 static bool IsPending(const scoped_refptr<TrackedCallback>& callback); 107 108 protected: 109 bool is_blocking() { 110 return !callback_.func; 111 } 112 bool is_required() { 113 return (callback_.func && 114 !(callback_.flags & PP_COMPLETIONCALLBACK_FLAG_OPTIONAL)); 115 } 116 bool is_optional() { 117 return (callback_.func && 118 (callback_.flags & PP_COMPLETIONCALLBACK_FLAG_OPTIONAL)); 119 } 120 bool has_null_target_loop() const { 121 return target_loop_ == NULL; 122 } 123 124 private: 125 // TrackedCallback and EnterBase manage dealing with how to invoke callbacks 126 // appropriately. Pepper interface implementations and proxies should not have 127 // to check the type of callback, block, or mark them complete explicitly. 128 friend class ppapi::thunk::subtle::EnterBase; 129 130 // Block until the associated operation has completed. Returns the result. 131 // This must only be called on a non-main thread on a blocking callback. 132 int32_t BlockUntilComplete(); 133 134 // Mark this object as complete and remove it from the tracker. This must only 135 // be called once. Note that running this may result in this object being 136 // deleted (so keep a reference if it'll still be needed). 137 void MarkAsCompleted(); 138 139 // This class is ref counted. 140 friend class base::RefCountedThreadSafe<TrackedCallback>; 141 virtual ~TrackedCallback(); 142 143 // Flag used by |PostAbort()| and |PostRun()| to check that we don't schedule 144 // the callback more than once. 145 bool is_scheduled_; 146 147 scoped_refptr<CallbackTracker> tracker_; 148 PP_Resource resource_id_; 149 bool completed_; 150 bool aborted_; 151 PP_CompletionCallback callback_; 152 153 // The MessageLoopShared on which this callback should be run. This will be 154 // NULL if we're in-process. 155 scoped_refptr<MessageLoopShared> target_loop_; 156 157 int32_t result_for_blocked_callback_; 158 // Used for pausing/waking the blocked thread if this is a blocking completion 159 // callback. Note that in-process, there is no lock, blocking callbacks are 160 // not allowed, and therefore this pointer will be NULL. 161 scoped_ptr<base::ConditionVariable> operation_completed_condvar_; 162 163 DISALLOW_IMPLICIT_CONSTRUCTORS(TrackedCallback); 164}; 165 166} // namespace ppapi 167 168#endif // PPAPI_SHARED_IMPL_TRACKED_CALLBACK_H_ 169