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      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 #include "media/base/serial_runner.h"
      6 
      7 #include "base/bind.h"
      8 #include "base/callback_helpers.h"
      9 #include "base/location.h"
     10 #include "base/message_loop/message_loop_proxy.h"
     11 #include "base/single_thread_task_runner.h"
     12 
     13 namespace media {
     14 
     15 // Converts a Closure into a bound function accepting a PipelineStatusCB.
     16 static void RunClosure(
     17     const base::Closure& closure,
     18     const PipelineStatusCB& status_cb) {
     19   closure.Run();
     20   status_cb.Run(PIPELINE_OK);
     21 }
     22 
     23 // Converts a bound function accepting a Closure into a bound function
     24 // accepting a PipelineStatusCB. Since closures have no way of reporting a
     25 // status |status_cb| is executed with PIPELINE_OK.
     26 static void RunBoundClosure(
     27     const SerialRunner::BoundClosure& bound_closure,
     28     const PipelineStatusCB& status_cb) {
     29   bound_closure.Run(base::Bind(status_cb, PIPELINE_OK));
     30 }
     31 
     32 // Runs |status_cb| with |last_status| on |task_runner|.
     33 static void RunOnTaskRunner(
     34     const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
     35     const PipelineStatusCB& status_cb,
     36     PipelineStatus last_status) {
     37   // Force post to permit cancellation of a series in the scenario where all
     38   // bound functions run on the same thread.
     39   task_runner->PostTask(FROM_HERE, base::Bind(status_cb, last_status));
     40 }
     41 
     42 SerialRunner::Queue::Queue() {}
     43 SerialRunner::Queue::~Queue() {}
     44 
     45 void SerialRunner::Queue::Push(const base::Closure& closure) {
     46   bound_fns_.push(base::Bind(&RunClosure, closure));
     47 }
     48 
     49 void SerialRunner::Queue::Push(
     50     const BoundClosure& bound_closure) {
     51   bound_fns_.push(base::Bind(&RunBoundClosure, bound_closure));
     52 }
     53 
     54 void SerialRunner::Queue::Push(
     55     const BoundPipelineStatusCB& bound_status_cb) {
     56   bound_fns_.push(bound_status_cb);
     57 }
     58 
     59 SerialRunner::BoundPipelineStatusCB SerialRunner::Queue::Pop() {
     60   BoundPipelineStatusCB bound_fn = bound_fns_.front();
     61   bound_fns_.pop();
     62   return bound_fn;
     63 }
     64 
     65 bool SerialRunner::Queue::empty() {
     66   return bound_fns_.empty();
     67 }
     68 
     69 SerialRunner::SerialRunner(const Queue& bound_fns,
     70                            const PipelineStatusCB& done_cb)
     71     : task_runner_(base::MessageLoopProxy::current()),
     72       bound_fns_(bound_fns),
     73       done_cb_(done_cb),
     74       weak_factory_(this) {
     75   // Respect both cancellation and calling stack guarantees for |done_cb|
     76   // when empty.
     77   if (bound_fns_.empty()) {
     78     task_runner_->PostTask(FROM_HERE,
     79                            base::Bind(&SerialRunner::RunNextInSeries,
     80                                       weak_factory_.GetWeakPtr(),
     81                                       PIPELINE_OK));
     82     return;
     83   }
     84 
     85   RunNextInSeries(PIPELINE_OK);
     86 }
     87 
     88 SerialRunner::~SerialRunner() {}
     89 
     90 scoped_ptr<SerialRunner> SerialRunner::Run(
     91     const Queue& bound_fns, const PipelineStatusCB& done_cb) {
     92   scoped_ptr<SerialRunner> callback_series(
     93       new SerialRunner(bound_fns, done_cb));
     94   return callback_series.Pass();
     95 }
     96 
     97 void SerialRunner::RunNextInSeries(PipelineStatus last_status) {
     98   DCHECK(task_runner_->BelongsToCurrentThread());
     99   DCHECK(!done_cb_.is_null());
    100 
    101   if (bound_fns_.empty() || last_status != PIPELINE_OK) {
    102     base::ResetAndReturn(&done_cb_).Run(last_status);
    103     return;
    104   }
    105 
    106   BoundPipelineStatusCB bound_fn = bound_fns_.Pop();
    107   bound_fn.Run(base::Bind(
    108       &RunOnTaskRunner,
    109       task_runner_,
    110       base::Bind(&SerialRunner::RunNextInSeries, weak_factory_.GetWeakPtr())));
    111 }
    112 
    113 }  // namespace media
    114