Class for implementing a "delay line" channel. More...

#include <delaychan.h>

Inheritance diagram for PDelayChannel:

Collaboration diagram for PDelayChannel:

Public Member Functions
Overrides from class PChannel
virtual PBoolean	Read (void *buf, PINDEX len)
	Low level read from the file channel. More...

virtual PBoolean	Write (const void *buf, PINDEX len)
	Low level write to the file channel. More...

Public Member Functions inherited from PIndirectChannel
	PIndirectChannel ()
	Create a new indirect channel without any channels to redirect to. More...

	~PIndirectChannel ()
	Close the indirect channel, deleting read/write channels if desired. More...

Comparison	Compare (const PObject &obj) const
	Determine if the two objects refer to the same indirect channel. More...

virtual PString	GetName () const
	Get the name of the channel. More...

virtual P_INT_PTR	GetHandle () const
	Get the OS specific handle for the PSoundChannel. More...

virtual PBoolean	Close ()
	Close the channel. More...

virtual PBoolean	IsOpen () const
	Determine if the channel is currently open and read and write operations can be executed on it. More...

virtual int	ReadChar ()
	Read a single character from the channel. More...

virtual PBoolean	Shutdown (ShutdownValue option)
	Close one or both of the data streams associated with a channel. More...

virtual bool	SetLocalEcho (bool localEcho)
	Set local echo mode. More...

virtual PChannel *	GetBaseReadChannel () const
	This function returns the eventual base channel for reading of a series of indirect channels provided by descendents of `PIndirectChannel`. More...

virtual PChannel *	GetBaseWriteChannel () const
	This function returns the eventual base channel for writing of a series of indirect channels provided by descendents of `PIndirectChannel`. More...

virtual PString	GetErrorText (ErrorGroup group=NumErrorGroups) const
	Get error message description. More...

PBoolean	Open (PChannel &channel)
	Set the channel for both read and write operations. More...

PBoolean	Open (PChannel *channel, PBoolean autoDelete=true)
	Set the channel for both read and write operations. More...

PBoolean	Open (PChannel readChannel, PChannel writeChannel, PBoolean autoDeleteRead=true, PBoolean autoDeleteWrite=true)
	Set the channel for both read and write operations. More...

PChannel *	Detach (ShutdownValue option=ShutdownReadAndWrite)
	Detach without closing the read/write channel. More...

PChannel *	GetReadChannel () const
	Get the channel used for read operations. More...

bool	SetReadChannel (PChannel *channel, bool autoDelete=true, bool closeExisting=false)
	Set the channel for read operations. More...

PChannel *	GetWriteChannel () const
	Get the channel used for write operations. More...

PBoolean	SetWriteChannel (PChannel *channel, bool autoDelete=true, bool closeExisting=false)
	Set the channel for read operations. More...

Public Member Functions inherited from PChannel
PBoolean	SetErrorValues (Errors errorCode, int osError, ErrorGroup group=LastGeneralError)
	Set error values to those specified. More...

virtual PINDEX	HashFunction () const
	Calculate a hash value for use in sets and dictionaries. More...

FILE *	FDOpen (const char *mode)
	Re-open the device using the stdio library. More...

void	SetReadTimeout (const PTimeInterval &time)
	Set the timeout for read operations. More...

PTimeInterval	GetReadTimeout () const
	Get the timeout for read operations. More...

PINDEX	GetLastReadCount () const
	Get the number of bytes read by the last Read() call. More...

PBoolean	ReadBlock (void *buf, PINDEX len)
	Read len bytes into the buffer from the channel. More...

PString	ReadString (PINDEX len)
	Read `len` character into a string from the channel. More...

void	SetWriteTimeout (const PTimeInterval &time)
	Set the timeout for write operations to complete. More...

PTimeInterval	GetWriteTimeout () const
	Get the timeout for write operations to complete. More...

virtual PBoolean	Write (const void buf, PINDEX len, const void )
	Low level write to the channel with marker. More...

virtual PINDEX	GetLastWriteCount () const
	Get the number of bytes written by the last Write() call. More...

PBoolean	WriteChar (int c)
	Write a single character to the channel. More...

PBoolean	WriteString (const PString &str)
	Write a string to the channel. More...

	~PChannel ()
	Close down the channel. More...

Errors	GetErrorCode (ErrorGroup group=NumErrorGroups) const
	Get normalised error code. More...

int	GetErrorNumber (ErrorGroup group=NumErrorGroups) const
	Get OS errro code. More...

virtual bool	ReadAsync (AsyncContext &context)
	Begin an asynchronous read from channel. More...

virtual void	OnReadComplete (AsyncContext &context)
	User callback function for when a `ReadAsync()` call has completed or timed out. More...

virtual bool	WriteAsync (AsyncContext &context)
	Begin an asynchronous write from channel. More...

virtual void	OnWriteComplete (AsyncContext &context)
	User callback function for when a WriteAsync() call has completed or timed out. More...

virtual bool	FlowControl (const void *flowData)
	Flow Control information Pass data to the channel for flowControl determination. More...

PBoolean	SetBufferSize (PINDEX newSize)
	Set the iostream buffer size for reads and writes. More...

PBoolean	SendCommandString (const PString &command)
	Send a command meta-string. More...

void	AbortCommandString ()
	Abort a command string that is in progress. 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 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 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 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 Member Functions
virtual void	Wait (PINDEX count, PTimeInterval &nextTick)

Protected Member Functions inherited from PIndirectChannel
virtual PBoolean	OnOpen ()
	This callback is executed when the Open() function is called with open channels. More...

Protected Member Functions inherited from PChannel
	PChannel (const PChannel &)

PChannel &	operator= (const PChannel &)

virtual PBoolean	ConvertOSError (P_INT_PTR libcReturnValue, ErrorGroup group=LastGeneralError)
	Convert an operating system error into platform independent error. More...

int	ReadCharWithTimeout (PTimeInterval &timeout)
	Read a character with specified timeout. More...

PBoolean	ReceiveCommandString (int nextChar, const PString &reply, PINDEX &pos, PINDEX start)

virtual int	os_errno () const

PBoolean	PXSetIOBlock (PXBlockType type, const PTimeInterval &timeout)

P_INT_PTR	GetOSHandleAsInt () const

int	PXClose ()

	PChannel ()
	Create the channel. More...

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

Protected Attributes
Mode	mode

unsigned	frameDelay

PINDEX	frameSize

PTimeInterval	maximumSlip

PTimeInterval	minimumDelay

PTimeInterval	nextReadTick

PTimeInterval	nextWriteTick

Protected Attributes inherited from PIndirectChannel
PChannel *	readChannel
	Channel for read operations. More...

PBoolean	readAutoDelete
	Automatically delete read channel on destruction. More...

PChannel *	writeChannel
	Channel for write operations. More...

PBoolean	writeAutoDelete
	Automatically delete write channel on destruction. More...

PReadWriteMutex	channelPointerMutex
	Race condition prevention on closing channel. More...

Protected Attributes inherited from PChannel
P_INT_PTR	os_handle
	The operating system file handle return by standard open() function. More...

Errors	lastErrorCode [NumErrorGroups+1]
	The platform independant error code. More...

int	lastErrorNumber [NumErrorGroups+1]
	The operating system error number (eg as returned by errno). More...

PINDEX	lastReadCount
	Number of byte last read by the Read() function. More...

PINDEX	lastWriteCount
	Number of byte last written by the Write() function. More...

PTimeInterval	readTimeout
	Timeout for read operations. More...

PTimeInterval	writeTimeout
	Timeout for write operations. More...

PString	channelName
	Name of channel. More...

PMutex	px_threadMutex

PXBlockType	px_lastBlockType

PThread *	px_readThread

PThread *	px_writeThread

PMutex	px_writeMutex

PThread *	px_selectThread [3]

PMutex	px_selectMutex [3]

Protected Attributes inherited from PObject
unsigned	m_traceContextIdentifier

Construction
enum	Mode { DelayReadsOnly, DelayWritesOnly, DelayReadsAndWrites }

	PDelayChannel (Mode mode, unsigned frameDelay, PINDEX frameSize=0, unsigned maximumSlip=250, unsigned minimumDelay=10)
	Create a new delay channel with the specified delays. More...

	PDelayChannel (PChannel &channel, Mode mode, unsigned frameDelay, PINDEX frameSize=0, unsigned maximumSlip=250, unsigned minimumDelay=10)
	Create a new delay channel with the specified delays and channel. More...

Additional Inherited Members
Public Types inherited from PChannel
enum	PXBlockType { PXReadBlock, PXWriteBlock, PXAcceptBlock, PXConnectBlock }

enum	Errors { NoError, NotFound, FileExists, DiskFull, AccessDenied, DeviceInUse, BadParameter, NoMemory, NotOpen, Timeout, Interrupted, BufferTooSmall, Miscellaneous, ProtocolFailure, Unavailable, NumNormalisedErrors }
	Normalised error codes. More...

enum	ErrorGroup { LastReadError, LastWriteError, LastGeneralError, NumErrorGroups }
	Error groups. More...

typedef PNotifierTemplate < PChannel::AsyncContext & >	AsyncNotifier

enum	ShutdownValue { ShutdownRead = 0, ShutdownWrite = 1, ShutdownReadAndWrite = 2 }

Static Public Member Functions inherited from PChannel
static PString	GetErrorText (Errors lastError, int osError=0)
	Get error message description. More...

Static Public Member Functions inherited from PObject
static Comparison	InternalCompareObjectMemoryDirect (const PObject obj1, const PObject obj2, PINDEX size)
	Internal function caled from CompareObjectMemoryDirect() More...

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)

Friends inherited from PObject

Detailed Description

Class for implementing a "delay line" channel.

This indirect channel can be placed in a channel I/O chain to limit the speed of I/O. This can be useful if blocking is not available and buffers could be overwritten if the I/O occurs at full speed.

There are two modes of operation. In stream more, data can be read/written no faster than a fixed time for a fixed number of bytes. So, for example, you can say than 320 bytes must take 20 milliseconds, and thus if the application writes 640 byets it will delay 40 milliseconds before the next write.

In frame mode, the rate limiting applies to individual read or write operations. So you can say that each read takes 30 milliseconds even if on 4 bytes is read, and the same time if 24 bytes are read.

Member Enumeration Documentation

enum PDelayChannel::Mode

Enumerator
DelayReadsOnly
DelayWritesOnly
DelayReadsAndWrites

Constructor & Destructor Documentation

PDelayChannel::PDelayChannel	(	Mode	mode,
		unsigned	frameDelay,
		PINDEX	frameSize = `0`,
		unsigned	maximumSlip = `250`,
		unsigned	minimumDelay = `10`
	)

Create a new delay channel with the specified delays.

A value of zero for the numBytes parameter indicates that the delay is in frame mode.

The maximum skip time is the number of milliseconds that the delay may "catch up" by using zero delays. This is caused by the Read() or Write() not being called for a time by external factors.

Parameters

mode	Mode for delay channel
frameDelay	Delay time in milliseconds
frameSize	Bytes to apply to the delay time.
maximumSlip	Maximum slip time in milliseconds
minimumDelay	Minimim delay (usually OS time slice)

PDelayChannel::PDelayChannel	(	PChannel &	channel,
		Mode	mode,
		unsigned	frameDelay,
		PINDEX	frameSize = `0`,
		unsigned	maximumSlip = `250`,
		unsigned	minimumDelay = `10`
	)

Create a new delay channel with the specified delays and channel.

A value of zero for the numBytes parameter indicates that the delay is in frame mode.

The maximum skip time is the number of milliseconds that the delay may "catch up" by using zero delays. This is caused by the Read() or Write() not being called for a time by external factors.

Parameters

channel	channel to use
mode	Mode for delay channel
frameDelay	Delay time in milliseconds
frameSize	Bytes to apply to the delay time.
maximumSlip	Maximum slip time in milliseconds
minimumDelay	Minimim delay (usually OS time slice)

Member Function Documentation

virtual PBoolean PDelayChannel::Read	(	void *	buf,
		PINDEX	len
	)

virtual

Low level read from the file channel.

The read timeout is ignored for file I/O. The GetLastReadCount() function returns the actual number of bytes read.

The GetErrorCode() function should be consulted after Read() returns false to determine what caused the failure.

Returns: true indicates that at least one character was read from the channel. false means no bytes were read due to timeout or some other I/O error.

Parameters

buf	Pointer to a block of memory to receive the read bytes.
len	Maximum number of bytes to read into the buffer.

Reimplemented from PIndirectChannel.

Reimplemented in PVXMLChannel.

virtual void PDelayChannel::Wait	(	PINDEX	count,
		PTimeInterval &	nextTick
	)

protectedvirtual

virtual PBoolean PDelayChannel::Write	(	const void *	buf,
		PINDEX	len
	)

virtual

Low level write to the file channel.

The write timeout is ignored for file I/O. The GetLastWriteCount() function returns the actual number of bytes written.

The GetErrorCode() function should be consulted after Write() returns false to determine what caused the failure.

Returns: true if at least len bytes were written to the channel.

Parameters

buf	Pointer to a block of memory to write.
len	Number of bytes to write.

Reimplemented from PIndirectChannel.

Reimplemented in PVXMLChannel.

Member Data Documentation

unsigned PDelayChannel::frameDelay

protected

PINDEX PDelayChannel::frameSize

protected

PTimeInterval PDelayChannel::maximumSlip

protected

PTimeInterval PDelayChannel::minimumDelay

protected

Mode PDelayChannel::mode

protected

PTimeInterval PDelayChannel::nextReadTick

protected

PTimeInterval PDelayChannel::nextWriteTick

protected

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

delaychan.h

Public Member Functions

Protected Member Functions

Protected Attributes

Construction

Additional Inherited Members

Detailed Description

Member Enumeration Documentation

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation