Abstract class defining I/O channel semantics. More...

#include <channel.h>

Inheritance diagram for PChannel:

Collaboration diagram for PChannel:

Classes
class	AsyncContext

class	AsyncContextBase
	Parameters for asynchronous I/O operation. More...

Public Types
enum	PXBlockType { PXReadBlock, PXWriteBlock, PXAcceptBlock, PXConnectBlock }

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

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

Overrides from class PObject
virtual Comparison	Compare (const PObject &obj) const
	Get the relative rank of the two strings. More...

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

Information functions
virtual PBoolean	IsOpen () const
	Determine if the channel is currently open. More...

virtual PString	GetName () const
	Get the platform and I/O channel type name of the channel. More...

virtual P_INT_PTR	GetHandle () const
	Get the integer operating system handle for the channel. More...

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

virtual PChannel *	GetBaseReadChannel () const
	Get the base channel of channel indirection using PIndirectChannel. More...

virtual PChannel *	GetBaseWriteChannel () const
	Get the base channel of channel indirection using PIndirectChannel. More...

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

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

virtual PBoolean	Read (void *buf, PINDEX len)
	Low level read from the channel. More...

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

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

Writing functions
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)
	Low level write to the channel. 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...

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
	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 ()

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

Protected Attributes
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
	PChannel ()
	Create the channel. More...

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

Error functions
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...

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

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

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

static PString	GetErrorText (Errors lastError, int osError=0)
	Get error message description. More...

Asynchronous I/O functions
typedef PNotifierTemplate < PChannel::AsyncContext & >	AsyncNotifier

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...

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

virtual PBoolean	Close ()
	Close the channel, shutting down the link to the data source. 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 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...

Additional Inherited Members
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

Abstract class defining I/O channel semantics.

An I/O channel can be a serial port, pipe, network socket or even just a simple file. Anything that requires opening and closing then reading and/or writing from.

A descendent would typically have constructors and an open function which enables access to the I/O channel it represents. The Read() and Write() functions would then be overridden to the platform and I/O specific mechanisms required.

The general model for a channel is that the channel accepts and/or supplies a stream of bytes. The access to the stream of bytes is via a set of functions that allow certain types of transfer. These include direct transfers, buffered transfers (via iostream) or asynchronous transfers.

The model also has the fundamental state of the channel being open or closed. A channel instance that is closed contains sufficient information to describe the channel but does not allocate or lock any system resources. An open channel allocates or locks the particular system resource. The act of opening a channel is a key event that may fail. In this case the channel remains closed and error values are set.

Member Typedef Documentation

typedef PNotifierTemplate<PChannel::AsyncContext &> PChannel::AsyncNotifier

Member Enumeration Documentation

enum PChannel::ErrorGroup

Error groups.

To aid in multithreaded applications where reading and writing may be happening simultaneously, read and write errors are separated from other errors.

Enumerator
LastReadError	Error during Read() operation.
LastWriteError	Error during Write() operation.
LastGeneralError	Error during other operation, eg Open()
NumErrorGroups

enum PChannel::Errors

Normalised error codes.

The error result of the last file I/O operation in this object.

Enumerator
NoError	No error.
NotFound	Open fail due to device or file not found.
FileExists	Open fail due to file already existing.
DiskFull	Write fail due to disk full.
AccessDenied	Operation fail due to insufficient privilege.
DeviceInUse	Open fail due to device already open for exclusive use.
BadParameter	Operation fail due to bad parameters.
NoMemory	Operation fail due to insufficient memory.
NotOpen	Operation fail due to channel not being open yet.
Timeout	Operation failed due to a timeout.
Interrupted	Operation was interrupted.
BufferTooSmall	Operations buffer was too small for data.
Miscellaneous	Miscellaneous error.
ProtocolFailure	High level protocol failure.
Unavailable	Cannot use channel at this time.
NumNormalisedErrors

enum PChannel::PXBlockType

Enumerator
PXReadBlock
PXWriteBlock
PXAcceptBlock
PXConnectBlock

enum PChannel::ShutdownValue

Enumerator
ShutdownRead
ShutdownWrite
ShutdownReadAndWrite

Constructor & Destructor Documentation

PChannel::PChannel ( )

protected

Create the channel.

PChannel::~PChannel ( )

Close down the channel.

PChannel::PChannel ( const PChannel & )

protected

Member Function Documentation

void PChannel::AbortCommandString ( )

Abort a command string that is in progress.

Note that as the SendCommandString() function blocks the calling thread when it runs, this can only be called from within another thread.

virtual PBoolean PChannel::Close ( )

virtual

Close the channel, shutting down the link to the data source.

Returns: true if the channel successfully closed.

Reimplemented in PRFC822Channel, PSSLChannel, PVXMLChannel, PPOP3Client, PMonitoredSocketChannel, PVXMLSession, PFile, XMPP::Stream, XMPP::Transport, PSMTPClient, PConsoleChannel, PFTPClient, PMemoryFile, PEthSocket, PQueueChannel, PIndirectChannel, PSSDP, XMPP::C2S::TCPTransport, PSoundChannelPortAudio, PVideoChannel, and PSerialChannel.

virtual Comparison PChannel::Compare ( const PObject & obj ) const

virtual

Get the relative rank of the two strings.

The system standard function, eg strcmp(), is used.

Returns: comparison of the two objects, EqualTo for same, LessThan for obj logically less than the object and GreaterThan for obj logically greater than the object.

Parameters

obj	Other PString to compare against.

Reimplemented from PObject.

Reimplemented in PFile, PIndirectChannel, and PMemoryFile.

virtual PBoolean PChannel::ConvertOSError	(	P_INT_PTR	libcReturnValue,
		ErrorGroup	group = `LastGeneralError`
	)

protectedvirtual

Convert an operating system error into platform independent error.

The internal error codes are set by this function. They may be obtained via the GetErrorCode() and GetErrorNumber() functions.

Returns: true if there was no error.

Parameters

libcReturnValue	Return value from standard library
group	Error group to set

Reimplemented in PSSLChannel, and PSocket.

FILE* PChannel::FDOpen ( const char * mode )

Re-open the device using the stdio library.

This closes the PChannel

Returns: stdio FILE * handle for the opened device.

virtual bool PChannel::FlowControl ( const void * flowData )

virtual

Flow Control information Pass data to the channel for flowControl determination.

Reimplemented in PVideoChannel.

virtual PChannel* PChannel::GetBaseReadChannel ( ) const

virtual

Get the base channel of channel indirection using PIndirectChannel.

This function returns the eventual base channel for reading of a series of indirect channels provided by descendents of PIndirectChannel.

The behaviour for this function is to return "this".

Returns: Pointer to base I/O channel for the indirect channel.

Reimplemented in PIndirectChannel.

virtual PChannel* PChannel::GetBaseWriteChannel ( ) const

virtual

Get the base channel of channel indirection using PIndirectChannel.

This function returns the eventual base channel for writing of a series of indirect channels provided by descendents of PIndirectChannel.

The behaviour for this function is to return "this".

Returns: Pointer to base I/O channel for the indirect channel.

Reimplemented in PIndirectChannel.

Errors PChannel::GetErrorCode ( ErrorGroup group = NumErrorGroups ) const

Get normalised error code.

Return the error result of the last file I/O operation in this object.

Returns: Normalised error code.

Parameters

group Error group to get

int PChannel::GetErrorNumber ( ErrorGroup group = NumErrorGroups ) const

Get OS errro code.

Return the operating system error number of the last file I/O operation in this object.

Returns: Operating System error code.

Parameters

group Error group to get

virtual PString PChannel::GetErrorText ( ErrorGroup group = NumErrorGroups ) const

virtual

Get error message description.

Return a string indicating the error message that may be displayed to the user. The error for the last I/O operation in this object is used.

Returns: Operating System error description string.

Parameters

group Error group to get

Reimplemented in PSSLChannel, PIndirectChannel, and PSoundChannelPortAudio.

static PString PChannel::GetErrorText	(	Errors	lastError,
		int	osError = `0`
	)

static

Get error message description.

Return a string indicating the error message that may be displayed to the user. The osError parameter is used unless zero, in which case the lastError parameter is used.

Returns: Operating System error description string.

Parameters

lastError	Error code to translate.
osError	OS error number to translate.

virtual P_INT_PTR PChannel::GetHandle ( ) const

virtual

Get the integer operating system handle for the channel.

Returns: standard OS descriptor integer.

Reimplemented in PIndirectChannel.

PINDEX PChannel::GetLastReadCount ( ) const

Get the number of bytes read by the last Read() call.

This will be from 0 to the maximum number of bytes as passed to the Read() call.

Note that the number of bytes read may often be less than that asked for. Aside from the most common case of being at end of file, which the applications semantics may regard as an exception, there are some cases where this is normal. For example, if a PTextFile channel on the MSDOS platform is read from, then the translation of CR/LF pairs to
characters will result in the number of bytes returned being less than the size of the buffer supplied.

Returns: the number of bytes read.

virtual PINDEX PChannel::GetLastWriteCount ( ) const

virtual

Get the number of bytes written by the last Write() call.

Note that the number of bytes written may often be less, or even more, than that asked for. A common case of it being less is where the disk is full. An example of where the bytes written is more is as follows. On a PTextFile channel on the MSDOS platform, there is translation of
to CR/LF pairs. This will result in the number of bytes returned being more than that requested.

Returns: the number of bytes written.

virtual PString PChannel::GetName ( ) const

inlinevirtual

Get the platform and I/O channel type name of the channel.

For example, it would return the filename in PFile type channels.

Returns: the name of the channel.

Reimplemented in PIPSocket, PFile, PConsoleChannel, PSoundChannelPortAudio, PIndirectChannel, and PVideoChannel.

References channelName.

P_INT_PTR PChannel::GetOSHandleAsInt ( ) const

inlineprotected

PTimeInterval PChannel::GetReadTimeout ( ) const

Get the timeout for read operations.

Note that this function may not be available, or meaningfull, for all channels. In that case it returns the previously set value.

Returns: time interval for read operations.

PTimeInterval PChannel::GetWriteTimeout ( ) const

Get the timeout for write operations to complete.

Note that this function may not be available, or meaningfull, for all channels. In that case it returns the previously set value.

Returns: time interval for writing.

virtual PINDEX PChannel::HashFunction ( ) const

virtual

Calculate a hash value for use in sets and dictionaries.

The hash function for strings will produce a value based on the sum of the first three characters of the string. This is a fairly basic function and make no assumptions about the string contents. A user may descend from PString and override the hash function if they can take advantage of the types of strings being used, eg if all strings start with the letter 'A' followed by 'B or 'C' then the current hash function will not perform very well.

Returns: hash value for string.

Reimplemented from PObject.

virtual PBoolean PChannel::IsOpen ( ) const

virtual

Determine if the channel is currently open.

This indicates that read and write operations can be executed on the channel. For example, in the PFile class it returns if the file is currently open.

Returns: true if the channel is open.

Reimplemented in PVXMLChannel, PMonitoredSocketChannel, PIndirectChannel, PVideoChannel, and PSoundChannelPortAudio.

virtual void PChannel::OnReadComplete ( AsyncContext & context )

virtual

User callback function for when a ReadAsync() call has completed or timed out.

The default behaviour calls the m_callback field of context.

Parameters

context Context for asynchronous operation

virtual void PChannel::OnWriteComplete ( AsyncContext & context )

virtual

User callback function for when a WriteAsync() call has completed or timed out.

The default behaviour calls the m_callback field of context.

Parameters

context Context for asynchronous operation

PChannel& PChannel::operator= ( const PChannel & )

protected

Referenced by P_timeval::P_timeval().

virtual int PChannel::os_errno ( ) const

protectedvirtual

Reimplemented in PSocket.

int PChannel::PXClose ( )

protected

PBoolean PChannel::PXSetIOBlock	(	PXBlockType	type,
		const PTimeInterval &	timeout
	)

protected

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

virtual

Low level read from the channel.

This function may block until the requested number of characters were read or the read timeout was reached. 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 in PSSLChannel, PNullChannel, PVXMLChannel, PMonitoredSocketChannel, PDelayChannel, PFile, PIndirectChannel, PVideoChannel, PMemoryFile, PEthSocket, PInternetProtocol, PQueueChannel, PUDPSocket, PTelnetSocket, PSoundChannelPortAudio, PSocket, and PTCPSocket.

virtual bool PChannel::ReadAsync ( AsyncContext & context )

virtual

Begin an asynchronous read from channel.

The read timeout is used as in other read operations, in this case calling the OnReadComplete() function.

If the channel is not capable of asynchronous read then returns false.

Note: the life time of the context and the m_buffer within that context must exceed the duration of the asynchronous operation. After OnReadComplete has been called, these objects may be destroyed.

Returns: true if the read was sucessfully queued.

Parameters

context Context for asynchronous operation

PBoolean PChannel::ReadBlock	(	void *	buf,
		PINDEX	len
	)

Read len bytes into the buffer from the channel.

This function uses Read(), so most remarks pertaining to that function also apply to this one. The only difference being that this function will not return until all of the bytes have been read, or an error occurs.

Returns: true if the read of len bytes was sucessfull.

Parameters

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

virtual int PChannel::ReadChar ( )

virtual

Read a single character from the channel.

If one was not available within the read timeout period, or an I/O error occurred, then the function gives with a -1 return value.

Note, normally the character read will be an 8 bit value, but for some derived classes, e.g. PConsoleChannel, this may be a code for special input.

Returns: byte read or -1 if no character could be read.

Reimplemented in PIndirectChannel, PConsoleChannel, and PInternetProtocol.

int PChannel::ReadCharWithTimeout ( PTimeInterval & timeout )

protected

Read a character with specified timeout.

This reads a single character from the channel waiting at most the amount of time specified for it to arrive. The timeout parameter is adjusted for amount of time it actually took, so it can be used for a multiple character timeout.

Returns: true if there was no error.

PString PChannel::ReadString ( PINDEX len )

Read len character into a string from the channel.

This function simply uses ReadBlock(), so all remarks pertaining to that function also apply to this one.

Returns: String that was read.

Parameters

len	Length of string data to read.

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

protected

PBoolean PChannel::SendCommandString ( const PString & command )

Send a command meta-string.

A meta-string is a string of characters that may contain escaped commands. The escape command is the \ as in the C language.

The escape commands are:

\a	alert (ascii value 7)
\b	backspace (ascii value 8)
\f	formfeed (ascii value 12)
\n	newline (ascii value 10)
\r	return (ascii value 13)
\t	horizontal tab (ascii value 9)
\v	vertical tab (ascii value 11)
\\	backslash
\ooo	where ooo is octal number, ascii value ooo
\xhh	where hh is hex number (ascii value 0xhh)
\0	null character (ascii zero)
\dns	delay for n seconds
\dnm	delay for n milliseconds
\s	characters following this, up to a \w command or the end of string, are to be sent to modem
\wns	characters following this, up to a \s, \d or another \w or the end of the string are expected back from the modem. If the string is not received within n seconds, a failed command is registered. The exception to this is if the command is at the end of the string or the next character in the string is the \s, \d or \w in which case all characters are ignored from the modem until n seconds of no data.
\wnm	as for above but timeout is in milliseconds.

Returns: true if the command string was completely processed.

Parameters

command Command to send to the channel

PBoolean PChannel::SetBufferSize ( PINDEX newSize )

Set the iostream buffer size for reads and writes.

Returns: true if the new buffer size was set.

Parameters

newSize New buffer size

PBoolean PChannel::SetErrorValues	(	Errors	errorCode,
		int	osError,
		ErrorGroup	group = `LastGeneralError`
	)

Set error values to those specified.

Return true if errorCode is NoError, false otherwise

Parameters

errorCode	Error code to translate.
osError	OS error number to translate.
group	Error group to set

virtual bool PChannel::SetLocalEcho ( bool localEcho )

virtual

Set local echo mode.

For some classes of channel, e.g. PConsoleChannel, data read by this channel is automatically echoed. This disables the function so things like password entry can work.

Default behaviour does nothing and return true if the channel is open.

Reimplemented in PIndirectChannel, PConsoleChannel, and PTelnetSocket.

void PChannel::SetReadTimeout ( const PTimeInterval & time )

Set the timeout for read operations.

This may be zero for immediate return of data through to PMaxTimeInterval which will wait forever for the read request to be filled.

Note that this function may not be available, or meaningfull, for all channels. In that case it is set but ignored.

Parameters

time	The new time interval for read operations.

void PChannel::SetWriteTimeout ( const PTimeInterval & time )

Set the timeout for write operations to complete.

This may be zero for immediate return through to PMaxTimeInterval which will wait forever for the write request to be completed.

Note that this function may not be available, or meaningfull, for all channels. In this case the parameter is et but ignored.

Parameters

time	The new time interval for write operations.

virtual PBoolean PChannel::Shutdown ( ShutdownValue option )

virtual

Close one or both of the data streams associated with a channel.

The default behavour is to do nothing and return false.

Returns: true if the shutdown was successfully performed.

Reimplemented in PSSLChannel, PIndirectChannel, and PSocket.

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

virtual

Low level write to the channel.

This function will block until the requested number of characters are written or the write timeout is reached. 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 in PRFC822Channel, PSSLChannel, PNullChannel, PVXMLChannel, PMonitoredSocketChannel, PDelayChannel, PFile, PIndirectChannel, XMPP::Stream, PMemoryFile, PEthSocket, PVideoChannel, PInternetProtocol, PTCPSocket, PQueueChannel, PTelnetSocket, PUDPSocket, PSoundChannelPortAudio, and PSocket.

Referenced by PTones::Write().

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

inlinevirtual

Low level write to the channel with marker.

    (H323plus Implementation)

This function will block until the requested number of characters are written or the write timeout is reached. The GetLastWriteCount() function returns the actual number of bytes written. By default it calls the Write(void *,len) function

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.

References Write().

Referenced by Write().

virtual bool PChannel::WriteAsync ( AsyncContext & context )

virtual

Begin an asynchronous write from channel.

The write timeout is used as in other write operations, in this case calling the OnWriteComplete() function.

If the channel is not capable of asynchronous write then returns false.

Note: the life time of the context and the m_buffer within that context must exceed the duration of the asynchronous operation. After OnWriteComplete has been called, these objects may be destroyed.

Returns: true of the write operation was succesfully queued.

Parameters

context Context for asynchronous operation

PBoolean PChannel::WriteChar ( int c )

Write a single character to the channel.

This function simply uses the Write() function so all comments on that function also apply.

Note that this asserts if the value is not in the range 0..255.

Returns: true if the byte was successfully written.

PBoolean PChannel::WriteString ( const PString & str )

Write a string to the channel.

This function simply uses the Write() function so all comments on that function also apply.

Returns: true if the character written.

Parameters

str	String to write

Member Data Documentation

PString PChannel::channelName

protected

Name of channel.

Referenced by GetName().

Errors PChannel::lastErrorCode[NumErrorGroups+1]

protected

The platform independant error code.

int PChannel::lastErrorNumber[NumErrorGroups+1]

protected

The operating system error number (eg as returned by errno).

PINDEX PChannel::lastReadCount

protected

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

PINDEX PChannel::lastWriteCount

protected

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

P_INT_PTR PChannel::os_handle

protected

The operating system file handle return by standard open() function.

PXBlockType PChannel::px_lastBlockType

protected

PThread* PChannel::px_readThread

protected

PMutex PChannel::px_selectMutex[3]

protected

PThread* PChannel::px_selectThread[3]

protected

PMutex PChannel::px_threadMutex

protected

PMutex PChannel::px_writeMutex

protected

PThread* PChannel::px_writeThread

protected

PTimeInterval PChannel::readTimeout

protected

Timeout for read operations.

PTimeInterval PChannel::writeTimeout

protected

Timeout for write operations.

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

channel.h

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