Async::FdWatch Class Reference

A class for watching file descriptors. More...

#include <AsyncFdWatch.h>

Inheritance diagram for Async::FdWatch:

Public Types
enum	FdWatchType { FD_WATCH_RD , FD_WATCH_WR }
	The type of the file descriptor watch. More...

Public Member Functions
	FdWatch (void)
	Default constructor.
	FdWatch (int fd, FdWatchType type)
	Constructor.
	~FdWatch (void)
	Destructor.
FdWatch &	operator= (FdWatch &&other)
	Assignment move operator.
int	fd (void) const
	Return the file descriptor being watched.
FdWatchType	type (void) const
	Return the type of this watch.
void	setEnabled (bool enabled)
	Enable or disable the watch.
bool	isEnabled (void) const
	Check if the watch is enabled or not.
void	setFd (int fd, FdWatchType type)
	Set the file descriptor to watch.

Public Attributes
sigc::signal< void, FdWatch * >	activity
	Signal to indicate that the descriptor is active.

Detailed Description

A class for watching file descriptors.

Author

Tobias Blomberg

Date

2003-03-19

Use this class to watch a file descriptor for activity. The example below creates a read watch on the standard input file descriptor. That is, every time a character is typed on the keyboard (or something is piped to the application) the onActivity method in instance this of class MyClass will be called. In the handler function, the data on the file descriptor should be read. Otherwise the handler function will be called over and over again.

Note

Since the stdin is line buffered, the ENTER key has to be pressed before anything will be shown.

#include <unistd.h>
#include <cstdio>
#include <iostream>
#include <AsyncCppApplication.h>
#include <AsyncFdWatch.h>
 
using namespace std;
using namespace Async;
 
class MyClass : public sigc::trackable
{
  public:
    MyClass(void)
    {
      stdin_watch = new FdWatch(STDIN_FILENO, FdWatch::FD_WATCH_RD);
      stdin_watch->activity.connect(mem_fun(*this, &MyClass::onActivity));
    }
    
    ~MyClass(void)
    {
      delete stdin_watch;
    }
 
  private:
    FdWatch *stdin_watch;
    
    void onActivity(FdWatch *watch)
    {
      char buf[1024];
      int cnt = read(watch->fd(), buf, sizeof(buf)-1);
      if (cnt == -1)
      {
        perror("read");
        Application::app().quit();
        return;
      }
      buf[cnt] = 0;
      cout << "Read from STDIN: " << buf << endl;
    }
};
 
int main(int argc, char **argv)
{
  CppApplication app;
  MyClass my_class;
  app.exec();
}

Examples

AsyncFdWatch_demo.cpp.

Definition at line 119 of file AsyncFdWatch.h.

Member Enumeration Documentation

FdWatchType

enum Async::FdWatch::FdWatchType

The type of the file descriptor watch.

Enumerator
FD_WATCH_RD	File descriptor watch for incoming data.
FD_WATCH_WR	File descriptor watch for outgoing data.

Definition at line 125 of file AsyncFdWatch.h.

Constructor & Destructor Documentation

FdWatch() [1/2]

Async::FdWatch::FdWatch

(

void

)

Default constructor.

Create a disabled FdWatch. Use the setFd function to set the filedescriptor to watch and the type of watch.

FdWatch() [2/2]

Async::FdWatch::FdWatch	(	int	fd,
		FdWatchType	type )

Constructor.

Add the given file descriptor to the watch list and watch it for incoming data (FD_WATCH_RD) or write buffer space available (FD_WATCH_WR).

Parameters

fd	The file descriptor to watch
type	The type of watch to create (see FdWatchType)

~FdWatch()

Async::FdWatch::~FdWatch

(

void

)

Destructor.

Member Function Documentation

fd()

int Async::FdWatch::fd ( void ) const

inline

Return the file descriptor being watched.

Returns

Returns the file descriptor

Examples

AsyncFdWatch_demo.cpp.

Definition at line 170 of file AsyncFdWatch.h.

isEnabled()

bool Async::FdWatch::isEnabled ( void ) const

inline

Check if the watch is enabled or not.

Returns

Returns true if the watch is enabled, or else false.

Definition at line 189 of file AsyncFdWatch.h.

operator=()

FdWatch & Async::FdWatch::operator=

(

FdWatch &&

other

)

Assignment move operator.

Parameters

other

The object to move data from

Returns

Returns a reference to this object

The move operator move the state of a specified FdWatch object into this object. After the move, the state of the other object will be the same as if it had just been default constructed.

setEnabled()

void Async::FdWatch::setEnabled

(

bool

enabled

)

Enable or disable the watch.

Parameters

enabled

Set to true to enable the watch or false to disable it.

setFd()

void Async::FdWatch::setFd	(	int	fd,
		FdWatchType	type )

Set the file descriptor to watch.

Parameters

fd	The file descriptor to watch
type	The type of watch to create (see FdWatchType)

This function can be used at any time to change the file descriptor or type of watch. If the watch was disabled it will stay disabled until explicitly being enabled. If fd < 0 the watch will be disabled if it was enabled.

type()

FdWatchType Async::FdWatch::type ( void ) const

inline

Return the type of this watch.

Returns

Returns the type (see FdWatchType)

Definition at line 176 of file AsyncFdWatch.h.

Member Data Documentation

activity

sigc::signal<void, FdWatch*> Async::FdWatch::activity

Signal to indicate that the descriptor is active.

Parameters

watch

Pointer to the watch object

Definition at line 207 of file AsyncFdWatch.h.

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

• AsyncFdWatch.h