# FBB::MultiBuf(3bobcat)

## Writing multiple streams
(libbobcat-dev_6.11.00)

## 2005-2025

## NAME

FBB::MultiBuf - Selectively writes multiple streams

## SYNOPSIS

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

## DESCRIPTION

The FBB::MultiBuf class is a specialization of std::streambuf. It can be used to write selectively to multiple std::ostreams. Each std::ostream that is associated with a MultiBuf is given a mode-tag indicating whether the stream should always be used when information is inserted into the MultiBuf, just once, or not at all. Each of the stream's mode-tags may be set to any of the defined tag-values.

When the address of a MultiBuf is used to initialize a std::ostream the constructed std::ostream becomes an output-multiplexer: by inserting information into the std::ostream object, all std::ostream objects added to its MultiBuf buffer which have an active mode receive that information.

An MultiBuf object should be outlived by all active streams that are associated with it.

MultiBuf objects refer to std::ostreams which are passed to it, and not to their std::streambufs. So it is possible to change these std::ostream's std::streambufs without reinstalling the std::ostreams themselves.

No assumptions should be made about the order in which the std::ostream objects that are associated with the MultiBuf objects are visited when information is inserted.

## NAMESPACE

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

## INHERITS FROM

std::streambuf

## ENUMERATION

In the Mode enumeration the following values are defined:

- OFF:
  A std::ostream having this mode will not be used when information is inserted into a MultiBuf
- ON:
  A std::ostream having this mode will be used when information is inserted into a MultiBuf
- ONCE:
  A std::ostream having this mode will be used once, until the next flushing operation, when information is inserted into an MultiBuf
- RESET:
  A std::ostream having this mode will not be used when information is inserted into a MultiBuf. At a flush operation all ONCE modes will be set to RESET
- ALL:
  This mode is used in combination with the member remove to remove all std::ostream elements matching a specified std::ostream argument.

## TYPES

The following subtypes are defined in the class FBB:MultiBuf:

- iterator:
  This is a synonym of std::vector<stream>::iterator
- const_iterator:
  This is a synonym of std::vector<stream>::const_iterator

## NESTED CLASS

The class MultiBuf::stream is defined as a nested class of MultiBuf. It offers the following constructor and public members:

- stream(std::ostream &os, Mode mode = ON):
  The constructor stores a std::ostream object, and associates a Mode value with it.
- void setMode(Mode mode):
  This member is used to redefine the stream's Mode value.
- void mode() const:
  This member returns the stream's Mode value.
- operator std::ostream &():
  This member returns the stream's std::ostream.

## CONSTRUCTORS

- MultiBuf():
  The default constructor creates a MultiBuf object which contains no associated std::ostream objects.
- MultiBuf(std::ostream &os, Mode mode = ON):
  This constructor creates a MultiBuf object which is immediately associated with the std::ostream specified as its first argument.
- MultiBuf(std::vector<MultiBuf::stream> const &osvector):
  This constructor creates a MultiBuf object which is immediately associated with all std::ostream objects that are stored in the MultiBuf::stream elements of the specified vector.

Copy and move constructors (and assignment operators) are not available.

## MEMBER FUNCTIONS

All members of std::ostringstream and std::exception are available, as MultiBuf inherits from these classes.

- iterator begin():
  This member returns an iterator to the first stream element that is stored in a MultiBuf object.
- const_iterator begin():
  This member returns an iterator to the first (unmodifiable) stream element that is stored in a MultiBuf object.
- iterator end():
  This member returns an iterator pointing beyond the last stream element that is stored in a MultiBuf object.
- const_iterator end():
  This member returns an iterator pointing beyond the last (unmodifiable) stream element that is stored in a MultiBuf object.
- void insert(std::ostream &os, Mode mode = ON):
  This member adds the specified std::ostream using the specified Mode to the current set of stream objects. Note that if called multiple times for identical std::ostreams these objects are inserted multiple times as well.
- void insert(std::vector<stream> const &os):
  This member adds all stream objects stored in the os vector to the current set of stream objects.
- bool remove(std::ostream &os, Mode mode = ONCE):
  If os is stored in the MultiBuf it is removed, and true is returned. If mode ALL is specified all os objects that were stored in the MultiBuf object are removed (and true is returned). If the os object was not stored false is returned. To determine whether os has been stored in the MultiBuf object its address is compared to the addresses of the std::ostream objects that are stored inside the MultiBuf object: the object(s) having addresses &os is (are) removed.
- void void setOnce():
  This member will reset all the RESET Mode values of the stored stream objects to ONCE.
- size_t size() const:
  The number of streams currently serviced by the MultiBuf object is returned.

## EXAMPLE

    #include <iostream>
    #include <fstream>
    #include <bobcat/multibuf>

    using namespace std;
    using namespace FBB;

    int main()
    {
        MultiBuf  msb(cout);
        ostream         os(&msb);
        ofstream        out("out");

        msb.insert(out, MultiBuf::ONCE);

        os << "This is on cout and out\n"
              "This is on cout only\n";

        msb.setOnce();
        os << "This is on cout and out\n"
              "This is on cout only\n";
    }

## FILES

bobcat/multibuf - defines the class interface

## SEE ALSO

bobcat(7)

## BUGS

None Reported.

## BOBCAT PROJECT FILES

- https://fbb-git.gitlab.io/bobcat/: gitlab project page;

Debian Bobcat project files:

- libbobcat6: debian package containing the shared library, changelog and copyright note;
- libbobcat-dev: debian package containing the static library, headers, manual pages, and developer info;

## BOBCAT

Bobcat is an acronym of `Brokken's Own Base Classes And Templates'.

## COPYRIGHT

This is free software, distributed under the terms of the GNU General Public License (GPL).

## AUTHOR

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