FBB::OFilterStreambuf(3bobcat)
ostream filtering
(libbobcat-dev_4.08.03-x.tar.gz)
2005-2018
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:
- 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.
- 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.
- OFstreamBuf's default overflow() function ignores characters,
but specializations can override overflow() to process the received
characters ad lib.
- 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
- OFilterStreambuf():
This constructor creates a OFilterStreambuf object without
associating it with a destination (filtered) ostream.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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
- 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
- bobcat_4.08.03-x.dsc: detached signature;
- bobcat_4.08.03-x.tar.gz: source archive;
- bobcat_4.08.03-x_i386.changes: change log;
- libbobcat1_4.08.03-x_*.deb: debian package holding the
libraries;
- libbobcat1-dev_4.08.03-x_*.deb: debian package holding the
libraries, headers and manual pages;
- 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).