selector.3bobcat

Langue: en

Autres versions - même langue

Version: 348155 (ubuntu - 24/10/10)

Section: 3 (Bibliothèques de fonctions)

Sommaire

NAME

FBB::Selector - Timed delays, Alarms and Multiple File I/O.

SYNOPSIS

#include <bobcat/selector>
Linking option: -lbobcat

DESCRIPTION

FBB::Selector objects are wrappers around the select()(2) system calls and allow timed delays, alarm functionality and/or multiple file I/O. It requires the use of file descriptors, which are not an official part of C++. However, most operating systems offer file descriptors. Sockets are well-known file descriptors.

NAMESPACE

FBB
All constructors, members, operators and manipulators, mentioned in this man-page, are defined in the namespace FBB.

INHERITS FROM

-

CONSTRUCTORS

o
Selector():
This constructor initializes the object. The copy constructor is available.

MEMBER FUNCTIONS

o
void addExceptFd(int fd):
Adds a filedescriptor to the set of file descriptors that are monitored for exceptions (note these are not C++ exceptions. See man 2 select for details).
o
void addReadFd(int fd):
Adds a filedescriptor to the set of file descriptors that are monitored for reading.
o
void addWriteFd(int fd):
Adds a filedescriptor to the set of file descriptors that are monitored for writing.
o
int exceptFd():
Returns -1 of no more file descriptors are available in the exception category. Otherwise the next available file descriptor in the exception category is returned. Returning from wait(), this function can be called repeatedly until -1 is returned, servicing each available filedescriptor in turn.
o
void noAlarm():
This member prevents any timeout-alarm from occurring.
o
int nReady():
Returns the number of available file descriptors. 0 is returned at a timeout, -1: is returned when select(2) itself failed.
o
int readFd():
Returns -1 of no more file descriptors are available for reading. Otherwise the next available file descriptor for reading is returned. Returning from wait(), this function can be called repeatedly until -1 is returned, servicing each available filedescriptor in turn.
o
void rmExceptFd(int fd):
Removes a filedescriptor from the set of file descriptors that are monitored for exceptions (note these are not C++ exceptions. See man 2 select for details).
o
void rmReadFd(int fd):
Removes a filedescriptor from the set of file descriptors that are monitored for reading.
o
void rmWriteFd(int fd):
Removes a filedescriptor from the set of file descriptors that are monitored for writing.
o
void setAlarm(int sec, int usec = 0):
This member sets the alarm at the indicated seconds and micro-seconds. If no action occurred on one of the monitored file descriptions following the indicated amount of time, wait() will return with nReady() returning 0. The requested alarm time (sec + usec / 1e+6) may not be negative and may not exceed INT_MAX or an FBB::Errno exception (Selector::setAlarm()) will be thrown. A 0 alarm time specification results in wait() returning immediately. To switch off the alarm time use noAlarm().
o
int wait():
This member should be called to wait for activities on the installed file descriptors or timeout-period. The members exceptFd(), nReady(), readFd() and writeFd() show their defined behaviors only after wait() has returned. It throws an FBB::Errno exception when select() fails, which may very well indicate the end of any available input. Otherwise it returns the number of available file descriptors.
o
int writeFd():
Returns -1 of no more file descriptors are available for writing. Otherwise the next available file descriptor for writing is returned. Returning from wait(), this function can be called repeatedly until -1 is returned, servicing each available filedescriptor in turn.

EXAMPLE

 
 #include <string>
 #include <iostream>
 
 #include <bobcat/selector>
 #include <bobcat/errno>
 
 using namespace std;
 using namespace FBB;
 
 int main(int argc, char **argv, char **envp)
 {
     Selector selector;
 
     selector.setAlarm(5);               // every 5 secs: alarm fires
     selector.addReadFd(STDIN_FILENO);   // look also at cin
 
     try
     {
         while (true)
         {
             if (!selector.wait())           // 0: alarm fires
                 cout << "Are you still there?" << endl;                
             else
             {
                 string s;
                 if (!getline(cin, s) || !s.length())
                     return 0;
                 cout << "Thank you for: " << s << endl;
             }
         }
     }
     catch (Errno const &e)
     {
         cout << e.what() << endl;
     }
     return 0;
 }

FILES

bobcat/selector - defines the class interface

SEE ALSO

bobcat(7), select(2)

BUGS

None Reported.

DISTRIBUTION FILES

o
bobcat_2.08.01-x.dsc: detached signature;
o
bobcat_2.08.01-x.tar.gz: source archive;
o
bobcat_2.08.01-x_i386.changes: change log;
o
libbobcat1_2.08.01-x_*.deb: debian package holding the libraries;
o
libbobcat1-dev_2.08.01-x_*.deb: debian package holding the libraries, headers and manual pages;
o
http://sourceforge.net/projects/bobcat: public archive location;

BOBCAT

Bobcat is an acronym of `Brokken's Own Base Classes And Templates'. This is free software, distributed under the terms of the GNU General Public License (GPL).

AUTHOR

Frank B. Brokken (f.b.brokken@rug.nl).