PReadWriteMutex Class Reference

This class defines a thread synchronisation object. More...

#include <syncthrd.h>

Inheritance diagram for PReadWriteMutex:

Collaboration diagram for PReadWriteMutex:

Classes
struct	Nest

Public Member Functions
Construction
	PReadWriteMutex ()
	~PReadWriteMutex ()
Operations
void	StartRead ()
	This function attempts to acquire the mutex for reading. More...
void	EndRead ()
	This function attempts to release the mutex for reading. More...
void	StartWrite ()
	This function attempts to acquire the mutex for writing. More...
void	EndWrite ()
	This function attempts to release the mutex for writing. More...
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::map < PThreadIdentifier, Nest >	NestMap

Protected Member Functions
Nest *	GetNest ()
Nest &	StartNest ()
void	EndNest ()
void	InternalStartRead (Nest &nest)
void	InternalEndRead (Nest &nest)
void	InternalWait (Nest &nest, PSync &sync) const
Protected Member Functions inherited from PObject
	PObject ()
	Constructor for PObject, made protected so cannot ever create one on its own. More...

Protected Attributes
PSemaphore	m_readerSemaphore
PTimedMutex	m_readerMutex
unsigned	m_readerCount
PTimedMutex	m_starvationPreventer
PSemaphore	m_writerSemaphore
PTimedMutex	m_writerMutex
unsigned	m_writerCount
NestMap	m_nestedThreads
PMutex	m_nestingMutex
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

This class defines a thread synchronisation object.

This is a special type of mutual exclusion, where the excluded area may have multiple read threads but only one write thread and the read threads are blocked on write as well.

Member Typedef Documentation

typedef std::map<PThreadIdentifier, Nest> PReadWriteMutex::NestMap

protected

Constructor & Destructor Documentation

PReadWriteMutex::PReadWriteMutex

(

)

PReadWriteMutex::~PReadWriteMutex

(

)

Member Function Documentation

void PReadWriteMutex::EndNest ( )

protected

void PReadWriteMutex::EndRead

(

)

This function attempts to release the mutex for reading.

Referenced by PHTTPSpace::EndRead().

void PReadWriteMutex::EndWrite

(

)

This function attempts to release the mutex for writing.

Note, if the same thread had a read lock when the StartWrite() was called which has not yet been released by an EndRead() call then this will reacquire the read lock.

It should also be noted that a consequence of this is that another thread may acquire the write lock before the thread that regains the read lock. Thus it is impossibly to go straight from a write lock to read lock without the possiblility of the object being changed and application logic should take this into account.

Referenced by PHTTPSpace::EndWrite().

Nest* PReadWriteMutex::GetNest ( )

protected

void PReadWriteMutex::InternalEndRead ( Nest &  nest )

protected

void PReadWriteMutex::InternalStartRead ( Nest &  nest )

protected

void PReadWriteMutex::InternalWait ( Nest &  nest, PSync &  sync  ) const

protected

Nest& PReadWriteMutex::StartNest ( )

protected

void PReadWriteMutex::StartRead

(

)

This function attempts to acquire the mutex for reading.

This call may be nested and must have an equal number of EndRead() calls for the mutex to be released.

Referenced by PHTTPSpace::StartRead().

void PReadWriteMutex::StartWrite

(

)

This function attempts to acquire the mutex for writing.

This call may be nested and must have an equal number of EndWrite() calls for the mutex to be released.

Note, if the same thread had a read lock previous to this call then the read lock is automatically released and reacquired when EndWrite() is called, unless an EndRead() is called. The EndRead() and EndWrite() calls do not have to be strictly nested.

It should also be noted that a consequence of this is that another thread may acquire the write lock before the thread that previously had the read lock. Thus it is impossibly to go straight from a read lock to write lock without the possiblility of the object being changed and application logic should take this into account.

Referenced by PHTTPSpace::StartWrite().

Member Data Documentation

NestMap PReadWriteMutex::m_nestedThreads

protected

PMutex PReadWriteMutex::m_nestingMutex

protected

unsigned PReadWriteMutex::m_readerCount

protected

PTimedMutex PReadWriteMutex::m_readerMutex

protected

PSemaphore PReadWriteMutex::m_readerSemaphore

protected

PTimedMutex PReadWriteMutex::m_starvationPreventer

protected

unsigned PReadWriteMutex::m_writerCount

protected

PTimedMutex PReadWriteMutex::m_writerMutex

protected

PSemaphore PReadWriteMutex::m_writerSemaphore

protected

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The documentation for this class was generated from the following file:

• syncthrd.h