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