ppapi/shared_impl/tracked_callback.h

   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
  21 namespace ppapi {
  22
  23 class CallbackTracker;
  24 class MessageLoopShared;
  25 class Resource;
  26
  27 namespace thunk {
  28 namespace subtle {
  29 // For a friend declaration below.
  30 class 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.
  61 class 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_