These classes and templates implement a generic thread pooling mechanism. More...

#include <threadpool.h>

Inheritance diagram for PThreadPoolBase:

Collaboration diagram for PThreadPoolBase:

Classes
class	InternalWorkBase

class	WorkerThreadBase

Public Member Functions
	~PThreadPoolBase ()

virtual WorkerThreadBase *	CreateWorkerThread ()=0

virtual WorkerThreadBase *	AllocateWorker ()

virtual WorkerThreadBase *	NewWorker ()

unsigned	GetMaxWorkers () const

void	SetMaxWorkers (unsigned count)

unsigned	GetMaxUnits () const

void	SetMaxUnits (unsigned count)

Public Member Functions inherited from PObject
unsigned	GetTraceContextIdentifier () const
	Get PTRACE context identifier. More...

void	SetTraceContextIdentifier (unsigned id)

void	GetTraceContextIdentifier (PObject &obj)

void	GetTraceContextIdentifier (PObject *obj)

void	SetTraceContextIdentifier (const PObject &obj)

void	SetTraceContextIdentifier (const PObject *obj)

virtual	~PObject ()

virtual PObject *	Clone () const
	Create a copy of the class on the heap. More...

template<class CLS >
CLS *	CloneAs () const
	As for Clone() but converts to specified type. More...

virtual PINDEX	HashFunction () const
	This function yields a hash value required by the `PDictionary` class. More...

virtual const char *	GetClass (unsigned ancestor=0) const
	Get the current dynamic type of the object instance. More...

PBoolean	IsClass (const char *cls) const

virtual PBoolean	InternalIsDescendant (const char *clsName) const
	Determine if the dynamic type of the current instance is a descendent of the specified class. More...

__inline const PObject *	PTraceObjectInstance () const

virtual Comparison	Compare (const PObject &obj) const
	Compare the two objects and return their relative rank. More...

virtual Comparison	CompareObjectMemoryDirect (const PObject &obj) const
	Determine the byte wise comparison of two objects. More...

bool	operator== (const PObject &obj) const
	Compare the two objects. More...

bool	operator!= (const PObject &obj) const
	Compare the two objects. More...

bool	operator< (const PObject &obj) const
	Compare the two objects. More...

bool	operator> (const PObject &obj) const
	Compare the two objects. More...

bool	operator<= (const PObject &obj) const
	Compare the two objects. More...

bool	operator>= (const PObject &obj) const
	Compare the two objects. More...

virtual void	PrintOn (ostream &strm) const
	Output the contents of the object to the stream. More...

virtual void	ReadFrom (istream &strm)
	Input the contents of the object from the stream. More...

Protected Types
typedef std::vector < WorkerThreadBase * >	WorkerList_t

Protected Member Functions
	PThreadPoolBase (unsigned maxWorkerCount, unsigned maxWorkUnitCount, const char *threadName, PThread::Priority priority)

virtual bool	CheckWorker (WorkerThreadBase *worker)

void	StopWorker (WorkerThreadBase *worker)

Protected Member Functions inherited from PObject
	PObject ()
	Constructor for PObject, made protected so cannot ever create one on its own. More...

Protected Attributes
PMutex	m_listMutex

WorkerList_t	m_workers

unsigned	m_maxWorkerCount

unsigned	m_maxWorkUnitCount

unsigned	m_highWaterMark

PString	m_threadName

PThread::Priority	m_priority

Protected Attributes inherited from PObject
unsigned	m_traceContextIdentifier

Additional Inherited Members
Public Types inherited from PObject
enum	Comparison { LessThan = -1, EqualTo = 0, GreaterThan = 1 }
	Result of the comparison operation performed by the `Compare()` function. More...

Static Public Member Functions inherited from PObject
static const char *	Class ()
	Get the name of the class as a C string. More...

static __inline const PObject *	PTraceObjectInstance (const char *)

static __inline const PObject *	PTraceObjectInstance (const PObject *obj)

static Comparison	InternalCompareObjectMemoryDirect (const PObject obj1, const PObject obj2, PINDEX size)
	Internal function caled from CompareObjectMemoryDirect() More...

Friends inherited from PObject

Detailed Description

These classes and templates implement a generic thread pooling mechanism.

There are two forms, low level and high level. For high level, it is assumed that there is a pool of threads each with a queue of work items to be processed. TO use simply decare a class containing the void Work() function and create the poolwith PQueuedThreadPool. e.g.

class MyWork { void Work() { doIt(); } }

PQueuedThreadPool<MyWork> m_pool;

m_pool.AddWork(new MyWork());

To use low level, declare the following:

A class that describes a "unit" of work to be performed.

A class that described a worker thread within the pool. This class must be a descendant of PThreadPoolWorkerBase and must define the following member functions:

Constructor with one parameter declared as "PThreadPoolBase & threadPool"
unsigned GetWorkSize() const;
void OnAddWork(work_unit *);
void OnRemoveWork(work_unit *);

void Shutdown();
void Main();

A class that describes the thread pool itself. This is defined using PThreadPool template

Example declarations:

struct MyWorkUnit { PString work; };

class MyWorkerThread : public PThreadPoolWorkerBase { public: MyWorkerThread(PThreadPoolBase & threadPool) : PThreadPoolWorkerBase(threadPool) { }

void Main(); void Shutdown(); unsigned GetWorkSize() const; void OnAddWork(MyWorkUnit * work); void OnRemoveWork(MyWorkUnit * work); };

class SIPMainThreadPool : public PThreadPool<MyWorkUnit, MyWorkerThread> { public: virtual PThreadPoolWorkerBase * CreateWorkerThread() { return new MyWorkerThread(*this); } };

The worker thread member functions operate as follows:

Constructor Called whenever a new worker thread is required

void Main() Called when the worker thread starts up

unsigned GetWorkSize() Called whenever the thread pool wants to know how "busy" the thread is. This is used when deciding how to allocate new work units

void OnAddWork(work_unit *) Called to add a new work unit to the thread

void OnRemoveWork(work_unit *); Called to remove a work unit from the thread

void Shutdown(); Called to close down the worker thread

The thread pool is used simply by instantiation as shown below.

MyThreadPool myThreadPool(10, 30);

If the second parameter is zero, the first paramater sets the maximum number of worker threads that will be created. If the second parameter is not zero, this is the maximum number of work units each thread can handle. The first parameter is then the "quanta" in which worker threads will be allocated

Once instantiated, the AddWork and RemoveWork member functions can be used to add and remove work units as required. The thread pool code will take care of starting, stopping and load balancing worker threads as required.Base class for thread pools.