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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/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
     97