IODevice Class Reference

#include <Pt/System/IODevice.h>

Endpoint for I/O operations. More...

Inherits Selectable.

Inherited by TcpSocket, UdpSocket, FileDevice, and SerialDevice.

Public Member Functions
virtual	~IODevice ()
	Destructor.
void	close ()
	Closes the device.
void	setTimeout (std::size_t timeout)
	Sets the timeout for blocking I/O in milliseconds.
void	beginRead (char *buffer, std::size_t n)
	Begins to read data.
std::size_t	endRead ()
	Ends reading data.
std::size_t	read (char *buffer, std::size_t n)
	Read data from I/O device.
void	beginWrite (const char *buffer, std::size_t n)
	Begins to write data.
std::size_t	endWrite ()
	Ends writing data.
std::size_t	write (const char *buffer, std::size_t n)
	Write data to I/O device.
bool	seekable () const
	Returns true if device is seekable.
pos_type	seek (off_type offset, seekdir sd)
	Moves the read position to the given offset.
std::size_t	peek (char *buffer, std::size_t n)
	Peek data from I/O device without consuming them.
void	sync ()
	Synchronize device.
pos_type	position ()
	Returns the current I/O position.
bool	isEof () const
	Returns if the device has reached EOF.
Signal< IODevice & > &	inputReady ()
	Notifies about available data.
Signal< IODevice & > &	outputReady ()
	Notifies when data can be written.
bool	isReading () const
	Returns true if the device is reading.
bool	isWriting () const
	Returns true if the device is writing.
EventLoop *	loop () const
	Returns the used event loop.
void	setActive (EventLoop &parent)
	Sets the parent loop, so that operations can be run.
void	detach ()
	Remove from event loop and cancels outstanding operations.
void	cancel ()
	Cancels all operations.
bool	run ()
	Run operation if it is ready.
EventLoop *	parent () const
	Returns the used event loop.

Protected Member Functions
	IODevice ()
	Default Constructor.
virtual void	onCancel ()
	Blocks until operation has cancelled.
void	post ()
	Posts this selectable to its event loop from any thread.
virtual void	onAttach (EventLoop &)
	Attached to loop.
virtual void	onDetach (EventLoop &)
	Detached from loop.
virtual bool	onRun ()=0
	Check if ready and run.

Detailed Description

IODevice is the endpoint for I/O. It is a Selectable. A file, a pipe end, and a serial port are IODevice types. I/O buffers and I/O streams use this endpoint, so a standard C++ stream can be built at runtime.

read() and write() transfer bytes and may return fewer than requested. They throw IOError on failure. When the device reaches the end of the stream, isEof() is true. setTimeout() limits how long a blocking transfer waits. close() releases the endpoint.

beginRead() and beginWrite() start an asynchronous transfer. The device must be attached to an EventLoop with setActive(). When the transfer finishes, inputReady or outputReady is emitted. endRead() and endWrite() complete the operation and return the number of bytes. One read and one write may run concurrently and complete independently; starting a second read or a second write before the first of that same direction ends is rejected.

Some devices can seek. seekable() reports that. seek() and position() throw IOError when the device cannot seek. peek() copies bytes without consuming them. sync() commits written data to the device.

class Reader
{
    public:
        explicit Reader(Pt::System::IODevice& device)
        : _device(&device)
        {
            _device->inputReady() += Pt::slot(*this, &Reader::onInput);
        }
 
        void begin()
        {
            _device->beginRead(_buffer, sizeof(_buffer));
        }
 
        void onInput(Pt::System::IODevice& device)
        {
            device.endRead();
            device.beginRead(_buffer, sizeof(_buffer));
        }
 
    private:
        Pt::System::IODevice* _device;
        char _buffer[256];
};

Member Function Documentation

read()

std::size_t read	(	char *	buffer,
		std::size_t	n )

Reads up to n bytes and stores them in buffer. Returns the number of bytes read, which may be less than requested and even 0 if the device operates in asynchronous (non-blocking) mode. In case of EOF the IODevice is set to eof.

Parameters

buffer	buffer where to place the data to be read.
n	number of bytes to read

Returns

number of bytes read, which may be less than requested.

Exceptions

IOError

write()

std::size_t write	(	const char *	buffer,
		std::size_t	n )

Writes n bytes from buffer to this I/O device. Returns the number of bytes written, which may be less than requested. In case of EOF the IODevice is set to eof.

Exceptions

IOError

seek()

pos_type seek	(	off_type	offset,
		seekdir	sd )

Exceptions

IOError

peek()

std::size_t peek	(	char *	buffer,
		std::size_t	n )

Exceptions

IOError

sync()

void sync

(

)

Commits written data to physical device.

Exceptions

IOError

position()

pos_type position

(

)

The current I/O position is returned or an IOError is thrown if the device is not seekable. Seekability can be tested with seekable().

Exceptions

IOError

inputReady()

Signal< IODevice & > & inputReady

(

)

This signal is send when the IODevice is monitored in an EventLoop and data becomes available.

outputReady()

Signal< IODevice & > & outputReady

(

)

This signal is send when the IODevice is monitored in an EventLoop and the device is ready to write data.