media/base/serial_runner.cc

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