Provided by: libbobcat-dev_3.19.01-1ubuntu1_amd64 
NAME
FBB::OFilterStreambuf - Base class for std::ostream filtering
SYNOPSIS
#include <bobcat/ofilterstreambuf>
Linking option: -lbobcat
DESCRIPTION
The FBB::OFilterStreambuf class is a specialization of the std::streambuf class and can be
used as a base class for classes implementing ostream-filtering.
Ostream filtering is defined here as the process by which inserted characters are subject
to processing before they are passed on to another (filtered) ostream object (or they may
be rejected). The filtering may also result in inserting additional information into the
filtered ostream.
Chaining of filters is also possible: the filtered ostream may itself use an
OFilterStreambuf to filter its received information before passing it on to yet another
ostream.
As OFilterStreambuf inherits from std::streambuf an OFilterStreambuf object can be used to
provide an ostream object with a std::streambuf. Information inserted into such a stream
travels the following route:
o The information is converted to characters using the standard conversion facilities
implemented by std::ostream objects. E.g., when inserting the value 123 this value
is converted to the characters ’1’, ’2’ and ’3’, respectively.
o Each of the characters is then offered (in turn) to the std::streambuf that is
associated with the ostream object. In particular, the std::streambuf’s overflow()
member is called.
o OFstreamBuf’s default overflow() function ignores characters, but specializations
can override overflow() to process the received characters ad lib.
o A overriding overflow() function has access to the member OFstreambuf::out() which
is a reference to the std::ostream receiving the filtered information. To
implement a simple copy-filter (i.e., all characters are accepted as-is) a class
must be derived from OFilterStreambuf providing an overriding implementation of
overflow(), e.g., as follows:
int DerivedClass::overflow(int ch)
{
out().put(ch);
}
Next this std::streambuf specialization can be associated with an ostream into
which information to be `copy filtered’ can be inserted (cf. the EXAMPLE section
below).
NAMESPACE
FBB
All constructors, members, operators and manipulators, mentioned in this man-page, are
defined in the namespace FBB.
INHERITS FROM
std::streambuf
CONSTRUCTORS
o OFilterStreambuf():
This constructor creates a OFilterStreambuf object without associating it with a
destination (filtered) ostream.
o OFilterStreambuf(std::string const &fname, openmode mode = std::ios::out):
This constructor creates a OFilterStreambuf object and opens a private
std::ofstream object whose filename is provided and that should receive the
filtered information.
o OFilterStreambuf(char const *fname, openmode mode = std::ios::out):
Same as the previous constructor, expecting a char const * defining the name of the
private std::ofstream object.
o OFilterStreambuf(std::ostream &out):
This constructor creates a OFilterStreambuf object and will insert any filtered
information into the provided ostream object. The class’s destructor closes the
destination (filtered) stream (cf. the description of close() below).
MEMBER FUNCTIONS
All members of std::ostreambuf are available, as FBB::OFilterStreambuf inherits from that
class. In particular, derived classes should provide their own implementation of int
underflow(int ch) to implement any non-trivial filtering.
o void close():
This member calls the streambuf::sync() member to flush any pending information to
the destination (filtered) stream and then closes the destination stream. Note that
the default sync() member performs no special actions but it can be overridden by
derived classes to flush the destination stream just prior to its closing.
o void open(std::string const &fname, openmode mode = std::ios::out):
This member closes the current destination (filtered) std::ostream object and
associates the OFilterStreambuf object with a private std::ofstream object whose
filename is provided and that should receive subsequently filtered information.
o void open(char const *fname, openmode mode = std::ios::out):
Same as the previous member, but using a char const * to specify the name of the
private std::ofstream object to receive the filtered information.
o void open(std::ostream &out):
This member closes the current destination (filtered) std::ostream object and
associates the OFilterStreambuf object with the provided ostream object.
PROTECTED MEMBER FUNCTION
o std::ostream &out() const:
This member is available to derived classes to insert information into the
destination (filtered) stream.
EXAMPLE
#include <iostream>
#include <cctype>
#include <bobcat/ofilterstreambuf>
class NoDigits: public FBB::OFilterStreambuf
{
private:
int overflow(int ch) override
{
if (not isdigit(ch))
out().put(ch);
return ch;
}
int sync() override
{
out() << flush;
return 0;
}
};
using namespace FBB;
using namespace std;
int main()
{
NoDigits nod(cout); // no digits to cout
ostream out(&nod);
out << in.rdbuf(); // rm digits from cin
return 0;
}
FILES
bobcat/ofilterstreambuf - defines the class interface
SEE ALSO
bobcat(7), ifilterstreambuf(3bobcat)
BUGS
None Reported.
DISTRIBUTION FILES
o bobcat_3.19.01-x.dsc: detached signature;
o bobcat_3.19.01-x.tar.gz: source archive;
o bobcat_3.19.01-x_i386.changes: change log;
o libbobcat1_3.19.01-x_*.deb: debian package holding the libraries;
o libbobcat1-dev_3.19.01-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’.
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).