--- name: "multistreambuf" section: "3bobcat" platform: "linux" package: "libbobcat-dev" version: "4.08.06-1" release: "Debian 10 (Buster)" platforms: ["linux"] url: "https://new.carta.tech/multistreambuf" --- # multistreambuf(3bobcat) Selectively writes multiple streams ## NAME FBB::MultiStreambuf - Selectively writes multiple streams ## SYNOPSIS **#include \**\ Linking option: *-lbobcat* ## DESCRIPTION The **FBB::MultiStreambuf** 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 **MultiStreambuf** is given a mode-tag indicating whether the stream should always be used when information is inserted into the **MultiStreambuf**, 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 **MultiStreambuf** 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 **MultiStreambuf** buffer which have an active mode receive that information. An **MultiStreambuf** object should be outlived by all active streams that are associated with it. **MultiStreambuf** 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 **MultiStreambuf** 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: - o **OFF**:\ A *std::ostream* having this mode will not be used when information is inserted into a **MultiStreambuf** - o **ON**:\ A *std::ostream* having this mode will be used when information is inserted into a **MultiStreambuf** - o **ONCE**:\ A *std::ostream* having this mode will be used once, until the next flushing operation, when information is inserted into an **MultiStreambuf** - o **RESET**:\ A *std::ostream* having this mode will not be used when information is inserted into a **MultiStreambuf**. At a flush operation all **ONCE** modes will be set to **RESET** - o **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:MultiStreambuf**: - o **iterator**:\ This is a synonym of *std::vector\::iterator* - o **const\_iterator**:\ This is a synonym of *std::vector\::const\_iterator* ## NESTED CLASS The class **MultiStreambuf::stream** is defined as a nested class of **MultiStreambuf**. It offers the following constructor and public members: - o **stream(std::ostream &os, Mode mode = ON)**:\ The constructor stores a *std::ostream* object, and associates a **Mode** value with it. - o **void setMode(Mode mode)**:\ This member is used to redefine the **stream**’s **Mode** value. - o **void mode() const**:\ This member returns the **stream**’s **Mode** value. - o **operator std::ostream &()**:\ This member returns the **stream**’s *std::ostream*. ## CONSTRUCTORS - o **MultiStreambuf()**:\ The default constructor creates a **MultiStreambuf** object which contains no associated *std::ostream* objects. - o **MultiStreambuf(std::ostream &os, Mode mode = ON)**:\ This constructor creates a **MultiStreambuf** object which is immediately associated with the *std::ostream* specified as its first argument. - o **MultiStreambuf(std::vector\ const &osvector)**:\ This constructor creates a **MultiStreambuf** object which is immediately associated with all *std::ostream* objects that are stored in the **MultiStreambuf::stream** elements of the specified vector. The copy constructor is available. ## MEMBER FUNCTIONS All members of *std::ostringstream* and *std::exception* are available, as **MultiStreambuf** inherits from these classes. - o **iterator begin()**:\ This member returns an iterator to the first **stream** element that is stored in a **MultiStreambuf** object. - o **const\_iterator begin()**:\ This member returns an iterator to the first (unmodifiable) **stream** element that is stored in a **MultiStreambuf** object. - o **iterator end()**:\ This member returns an iterator pointing beyond the last **stream** element that is stored in a **MultiStreambuf** object. - o **const\_iterator end()**:\ This member returns an iterator pointing beyond the last (unmodifiable) **stream** element that is stored in a **MultiStreambuf** object. - o **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. - o **void insert(std::vector\ const &os)**:\ This member adds all **stream** objects stored in the **os** vector to the current set of **stream** objects. - o **bool remove(std::ostream &os, Mode mode = ONCE)**:\ If *os* is stored in the **MultiStreambuf** it is removed, and *true* is returned. If mode *ALL* is specified all *os* objects that were stored in the **MultiStreambuf** 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 **MultiStreambuf** object its address is compared to the addresses of the *std::ostream* objects that are stored inside the **MultiStreambuf** object: the object(s) having addresses *&os* is (are) removed. - o **void void setOnce()**:\ This member will reset all the *RESET* **Mode** values of the stored **stream** objects to *ONCE*. - o **size\_t size() const**:\ The number of streams currently serviced by the **MultiStreambuf** object is returned. ## PROTECTED MEMBER FUNCTION The member listed in this section implements the tasks of the comparably named virtual function in the class’s private interface. This separates the redefinable interface from the user-interface. The class **MultiStreamBuf** can, in accordance with Liskov’s Substitution Principle, be used as a *std:streambuf*; but it also offers a facility for classes deriving from **MultiStreamBuf**. This facility is listed here. - o **int pSync()**:\ The contents of the **MultiStreamBuf**’s internal buffer is written to each of the *std::ostream* objects to which the **MultiStreamBuf** object has access. ## EXAMPLE ``` #include #include #include using namespace std; using namespace FBB; int main() { MultiStreambuf msb(cout); ostream os(&msb); ofstream out("out"); msb.insert(out, MultiStreambuf::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/multistreambuf* - defines the class interface ## SEE ALSO [**bobcat**(7)](/bobcat/7.md) ## BUGS None Reported. ## DISTRIBUTION FILES - o *bobcat\_4.08.06-x.dsc*: detached signature; - o *bobcat\_4.08.06-x.tar.gz*: source archive; - o *bobcat\_4.08.06-x\_i386.changes*: change log; - o *libbobcat1\_4.08.06-x\_\*.deb*: debian package holding the libraries; - o *libbobcat1-dev\_4.08.06-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’. ## 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**).