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BackgroundMusic/BGMDriver/PublicUtility/CADispatchQueue.h
2016-02-19 16:25:34 +11:00

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/*
File: CADispatchQueue.h
Abstract: Part of CoreAudio Utility Classes
Version: 1.0.1
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*/
/*==================================================================================================
CADispatchQueue.h
==================================================================================================*/
#if !defined(__CADispatchQueue_h__)
#define __CADispatchQueue_h__
//==================================================================================================
// Includes
//==================================================================================================
// System Includes
#include <CoreFoundation/CFString.h>
#include <dispatch/dispatch.h>
// Standard Library Includes
#include <functional>
#include <vector>
/*==================================================================================================
CADispatchQueue
This class provides a wrapper for a libdispatch dispatch queue and several kinds of event
sources such as MIG servers, port death notifications and other mach port related support. Being
a libdispatch client, the unit of work is represented as either a function pointer and context
pointer pair or as a Block.
One thing to keep in mind when using a Block-based construct is that you get a copy of the
pointer but you do not get a copy of the memory that the pointer is pointing at. The net effect
is that if you have a task that frees the memory that is referenced by a subsequent task,
this second task would crash when dereferencing the pointer. This means that every task
needs to include some code to validate any pointers it is using before dereferencing them.
A common example of this problem comes up with C++ objects. Suppose you have an instance method
that creates a Block that calls other instance methods or accesses the object's fields. Suppose
further that the Block is submitted to a dispatch queue for execution. If the object gets
deallocated before the Block can run, the Block will crash. Thus, the Block needs to validate
that the "this" pointer is still valid when it executes.
Another place where this comes up often is when attempting to implment a function by dispatching
the work asynchronously. Any arguments to the function that point to the stack will be invalid.
This is particularly troublesome inside of a MIG function.
Still another common issue with using Blocks and dispatch functions with C++ is that it is vital
that no exceptions ever leave a Block or a dispatch function. If an exception was thrown out of
a block, the result would be undefined and probably would result in the program calling
the terminate() function in the standard C++ library (whose default implementation is to call
abort(3)). Given that, all Blocks and dispatch functions that might end up throwing an exception
need to catch those exceptions.
==================================================================================================*/
class CADispatchQueue
{
#pragma mark Construction/Destruction
public:
CADispatchQueue(const char* inName);
CADispatchQueue(CFStringRef inName);
CADispatchQueue(CFStringRef inPattern, CFStringRef inName);
virtual ~CADispatchQueue();
private:
CADispatchQueue(const CADispatchQueue&);
CADispatchQueue& operator=(const CADispatchQueue&);
#pragma mark Execution Operations
public:
void Dispatch(bool inDoSync, dispatch_block_t inTask) const;
void Dispatch(UInt64 inNanoseconds, dispatch_block_t inTask) const;
void Dispatch(bool inDoSync, void* inTaskContext, dispatch_function_t inTask) const;
void Dispatch(UInt64 inNanoseconds, void* inTaskContext, dispatch_function_t inTask) const;
static void Dispatch_Global(dispatch_queue_priority_t inQueuePriority, bool inDoSync, dispatch_block_t inTask);
static void Dispatch_Global(dispatch_queue_priority_t inQueuePriority, UInt64 inNanoseconds, dispatch_block_t inTask);
static void Dispatch_Global(dispatch_queue_priority_t inQueuePriority, bool inDoSync, void* inTaskContext, dispatch_function_t inTask);
static void Dispatch_Global(dispatch_queue_priority_t inQueuePriority, UInt64 inNanoseconds, void* inTaskContext, dispatch_function_t inTask);
static void Dispatch_Main(bool inDoSync, dispatch_block_t inTask);
static void Dispatch_Main(UInt64 inNanoseconds, dispatch_block_t inTask);
static void Dispatch_Main(bool inDoSync, void* inTaskContext, dispatch_function_t inTask);
static void Dispatch_Main(UInt64 inNanoseconds, void* inTaskContext, dispatch_function_t inTask);
#pragma mark Event Sources
public:
void InstallMachPortDeathNotification(mach_port_t inMachPort, dispatch_block_t inNotificationTask);
void RemoveMachPortDeathNotification(mach_port_t inMachPort);
void InstallMachPortReceiver(mach_port_t inMachPort, dispatch_block_t inMessageTask);
void RemoveMachPortReceiver(mach_port_t inMachPort, dispatch_block_t inCompletionTask);
void RemoveMachPortReceiver(mach_port_t inMachPort, bool inDestroySendRight, bool inDestroyReceiveRight);
#pragma mark Implementation
public:
dispatch_queue_t GetDispatchQueue() const;
static CADispatchQueue& GetGlobalSerialQueue();
protected:
static void InitializeGlobalSerialQueue(void*);
struct EventSource
{
dispatch_source_t mDispatchSource;
mach_port_t mMachPort;
EventSource();
EventSource(dispatch_source_t inDispatchSource, mach_port_t inMachPort);
EventSource(const EventSource& inEventSource);
EventSource& operator=(const EventSource& inEventSource);
~EventSource();
void Retain();
void Release();
};
typedef std::vector<EventSource> EventSourceList;
dispatch_queue_t mDispatchQueue;
EventSourceList mPortDeathList;
EventSourceList mMachPortReceiverList;
static CADispatchQueue* sGlobalSerialQueue;
static dispatch_once_t sGlobalSerialQueueInitialized;
};
//==================================================================================================
#pragma mark CADispatchQueue Inline Method Implementations
//==================================================================================================
inline dispatch_queue_t CADispatchQueue::GetDispatchQueue() const
{
return mDispatchQueue;
}
inline CADispatchQueue::EventSource::EventSource()
:
mDispatchSource(NULL),
mMachPort(MACH_PORT_NULL)
{
}
inline CADispatchQueue::EventSource::EventSource(dispatch_source_t inDispatchSource, mach_port_t inMachPort)
:
mDispatchSource(inDispatchSource),
mMachPort(inMachPort)
{
}
inline CADispatchQueue::EventSource::EventSource(const EventSource& inEventSource)
:
mDispatchSource(inEventSource.mDispatchSource),
mMachPort(inEventSource.mMachPort)
{
Retain();
}
inline CADispatchQueue::EventSource& CADispatchQueue::EventSource::operator=(const EventSource& inEventSource)
{
Release();
mDispatchSource = inEventSource.mDispatchSource;
mMachPort = inEventSource.mMachPort;
Retain();
return *this;
}
inline CADispatchQueue::EventSource::~EventSource()
{
Release();
}
inline void CADispatchQueue::EventSource::Retain()
{
if(mDispatchSource != NULL)
{
dispatch_retain(mDispatchSource);
}
}
inline void CADispatchQueue::EventSource::Release()
{
if(mDispatchSource != NULL)
{
dispatch_release(mDispatchSource);
mDispatchSource = NULL;
}
}
#endif // __CADispatchQueue_h__