Mac: implement orientation/motion shared memory data fetcher.

content/browser/device_orientation/data_fetcher_shared_memory_base.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/device_orientation/data_fetcher_shared_memory_base.h"
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/stl_util.h"
 #include "base/threading/thread.h"
 #include "base/timer/timer.h"
 
 namespace content {
 
 namespace {
 const int kPeriodInMilliseconds = 100;
 }
 
 class DataFetcherSharedMemoryBase::PollingThread : public base::Thread {
  public:
   PollingThread(const char* name, DataFetcherSharedMemoryBase* fetcher);
   virtual ~PollingThread();
 
-  void SetConsumers(int consumers_bitmask);
+  void AddConsumer(ConsumerType consumer_type);
+  void RemoveConsumer(ConsumerType consumer_type);
+
   unsigned GetConsumersBitmask() const { return consumers_bitmask_; }
 
  private:
 
   void DoPoll();
 
   unsigned consumers_bitmask_;
   DataFetcherSharedMemoryBase* fetcher_;
   scoped_ptr<base::RepeatingTimer<PollingThread> > timer_;
 
   DISALLOW_COPY_AND_ASSIGN(PollingThread);
 };
 
 // --- PollingThread methods
 
 DataFetcherSharedMemoryBase::PollingThread::PollingThread(
     const char* name, DataFetcherSharedMemoryBase* fetcher)
     : base::Thread(name), consumers_bitmask_(0), fetcher_(fetcher) {
 }
 
 DataFetcherSharedMemoryBase::PollingThread::~PollingThread() {
 }
 
-void DataFetcherSharedMemoryBase::PollingThread::SetConsumers(
-    int consumers_bitmask) {
-  consumers_bitmask_ = consumers_bitmask;
-  if (!consumers_bitmask_) {
-    timer_.reset(); // will also stop the timer.
+void DataFetcherSharedMemoryBase::PollingThread::AddConsumer(
+    ConsumerType consumer_type) {
+  DCHECK(fetcher_);
+  if (!fetcher_->Start(consumer_type))
     return;
-  }
+
+  consumers_bitmask_ |= consumer_type;
 
   if (!timer_)
     timer_.reset(new base::RepeatingTimer<PollingThread>());
 
   timer_->Start(FROM_HERE,
                 base::TimeDelta::FromMilliseconds(kPeriodInMilliseconds),
                 this, &PollingThread::DoPoll);
 }
 
+void DataFetcherSharedMemoryBase::PollingThread::RemoveConsumer(
+    ConsumerType consumer_type) {
+  DCHECK(fetcher_);
+  if (!fetcher_->Stop(consumer_type))
+    return;
+
+  consumers_bitmask_ ^= consumer_type;
+
+  if (!consumers_bitmask_)
+    timer_.reset(); // will also stop the timer.
+}
+
 void DataFetcherSharedMemoryBase::PollingThread::DoPoll() {
   DCHECK(fetcher_);
   DCHECK(consumers_bitmask_);
   fetcher_->Fetch(consumers_bitmask_);
 }
 
 // --- end of PollingThread methods
 
 DataFetcherSharedMemoryBase::DataFetcherSharedMemoryBase()
     :  started_consumers_(0) {
 }
 
 DataFetcherSharedMemoryBase::~DataFetcherSharedMemoryBase() {
   StopFetchingDeviceData(CONSUMER_TYPE_MOTION);
   StopFetchingDeviceData(CONSUMER_TYPE_ORIENTATION);
 
   // make sure polling thread stops asap.
   if (polling_thread_)
     polling_thread_->Stop();
 
   STLDeleteContainerPairSecondPointers(shared_memory_map_.begin(),
       shared_memory_map_.end());
 }
 
 bool DataFetcherSharedMemoryBase::StartFetchingDeviceData(
     ConsumerType consumer_type) {
   if (started_consumers_ & consumer_type)
     return true;
 
-  if (!Start(consumer_type))
-    return false;
+  if (IsPolling()) {
+    if (!InitAndStartPollingThreadIfNecessary())
+      return false;
+    polling_thread_->message_loop()->PostTask(
+        FROM_HERE,
+        base::Bind(&PollingThread::AddConsumer,
+                   base::Unretained(polling_thread_.get()),
+                   consumer_type));
+  } else {
+    if (!Start(consumer_type))
+      return false;
+  }
 
   started_consumers_ |= consumer_type;
 
-  if (IsPolling()) {
-    if (!InitAndStartPollingThreadIfNecessary()) {
-      Stop(consumer_type);
-      started_consumers_ ^= consumer_type;
-      return false;
-    }
-    polling_thread_->message_loop()->PostTask(
-        FROM_HERE,
-        base::Bind(&PollingThread::SetConsumers,
-                   base::Unretained(polling_thread_.get()),
-                   started_consumers_));
-  }
   return true;
 }
 
 bool DataFetcherSharedMemoryBase::StopFetchingDeviceData(
     ConsumerType consumer_type) {
   if (!(started_consumers_ & consumer_type))
     return true;
 
-  if (!Stop(consumer_type))
-    return false;
-
-  started_consumers_ ^= consumer_type;
-
   if (IsPolling()) {
     polling_thread_->message_loop()->PostTask(
         FROM_HERE,
-        base::Bind(&PollingThread::SetConsumers,
+        base::Bind(&PollingThread::RemoveConsumer,
                    base::Unretained(polling_thread_.get()),
-                   started_consumers_));
+                   consumer_type));
+  } else {
+    if (!Stop(consumer_type))
+      return false;
   }
+
+  started_consumers_ ^= consumer_type;
+
   return true;
 }
 
 base::SharedMemoryHandle
 DataFetcherSharedMemoryBase::GetSharedMemoryHandleForProcess(
     ConsumerType consumer_type, base::ProcessHandle process) {
   SharedMemoryMap::const_iterator it = shared_memory_map_.find(consumer_type);
   if (it == shared_memory_map_.end())
     return base::SharedMemory::NULLHandle();
 
@@ skipping 48 matching lines @@
       buffer_size))
     return shared_memory->memory();
   return NULL;
 }
 
 base::MessageLoop* DataFetcherSharedMemoryBase::GetPollingMessageLoop() const {
   return polling_thread_ ? polling_thread_->message_loop() : NULL;
 }
 
 }  // namespace content