# FBB::OFoldStream(3bobcat)

## Fold long lines
(libbobcat-dev_6.14.00)

## 2005-2026

## NAME

FBB::OFoldStream - Folds long lines

## SYNOPSIS

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

## DESCRIPTION

FBB::OFoldStream folds long lines written to it. The OFoldStream writes the (folded) lines to a second ostream which is either used by or opened by the OFoldStream object.

OFoldStream objects never fold lines in the middle of series of non-blank characters but will always break a line at white space characters. The resulting lines will always appear to the right of a configurable left margin and to the left of a configurable right margin. There is a somewhat pathological exception to this: if a word is too long to fit in between the margins then the word will exceed the right hand margin.

The indentation used for the left margins is configurable to either blanks (the default) or tabs. When tabs are used the width of a tab character is configurable, using a default of 8 positions in the destination stream.

OFoldStream is implemented as a wrapper class around std::ostream and FBB::OFoldBuf and a more complete description of the folding process can be found in the ofoldbuf(3bobcat) man page.

## NAMESPACE

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

## INHERITS FROM

std::ostream,
(and privately from FBB::OFoldBuf)

## ENUMERATION

The enumeration TabsOrBlanks is used to select tabs or blanks when writing the indentation. The default is blanks. When tabs are selected the display width of tabs characters can be configured as well (using the default of 8 positions for each tab-character). The enumeration has two values:

- BLANKS:
  The default, indicating that the left margin is specified and written as a number of blanks;
- TABS:
  Indicating that the left margin is specified and written as a number of tab-characters.

The enumeration TrailingBlanks is used to configure the OFoldStream object with respect to any trailing blanks that may appear on the final line. It is the same enumeration type as used with OFoldBuf (cf. ofoldbuf(3bobcat)) having two values:

- IGNORE_TRAILING_BLANKS:
  This indicates that trailing blanks appearing at the final line if it is not terminated by a newline should not be written to the destination std::ostream. This is the default used by OFoldStream objects.
- KEEP_TRAILING_BLANKS:
  This indicates that trailing blanks at the final line if it is not terminated by a newline should be written to the destination std::ostream

## CONSTRUCTORS

- OFoldStream():
  This constructor initializes an OFoldStream object but does not associate it with a destination stream. It uses the values 0, 80, BLANKS, and IGNORE_TRAILING_BLANKSfor, resp. its left margin, right margin left-margin characters and TrailingBlanks handling mode.

- OFoldStream(char const *fname, size_t leftIndent = 0, size_t rightMargin = 80, TabsOrBlanks tob = BLANKS, TrailingBlanks tb = IGNORE_TRAILING_BLANKS):
  This constructor initializes an OFoldStream object and opens (using std::ios::out) the destination stream using the name specified as its fname argument.

- OFoldStream(std::ostream &stream, size_t leftIndent = 0, size_t rightMargin = 80, TabsOrBlanks tob = BLANKS, TrailingBlanks tb = IGNORE_TRAILING_BLANKS):
  This constructor initializes an OFoldStream object and uses as its destination stream the std::ostream stream.

The destructor writes any buffered information to the destination stream and will then flush the destination stream.

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

## MEMBER FUNCTIONS

All members of std::ostream are available, as FBB::OFoldStream inherits from this class.

- void close():
  This member flushes any pending information to the destination stream and then closes the destination stream.

- void open(char const *fname, openmode mode = std::ios::out):
  This member associates the OFilterStream object with an std::ofstream object whose filename is provided and that should receive the folded information.

- void open(std::ostream &out):
  This member associates the OFilterStream object with the provided ostream object.

- void setMargins(size_t leftMargin, size_t rightMargin):
  This member can be used to modify the left- and right folding margins. Note that the left margin may also be modified using the FBB::lm and FBB::mlm manipulators.

- void setTrailingBlanks(TrailingBlanks tb):
  This member can be used to modify the currently used TrailingBlanks parameter.

- void useBlanks():
  This member can be used to select blanks to be used when inserting left margins.

- void useTabs(size_t tabWidth = 8):
  This member can be used to select tab-characters to be used when inserting left margins. The second parameter is used to specify the display width of a tab-character.

## STATIC MEMBER FUNCTIONS

- size_t leftMargin(std::ostream const &os):
  This member returns the current left margin setting of the OFoldStream object passed to it as its argument. The member defines a std::ostream parameter since in many cases the OFoldStream object will be used in functions themselves defining std::ostream parameters. Internally, the std::ostream's std::streambuf is down cast to an OFoldBuf and an FBB::Exception exception is thrown if that cast fails.
- size_t rightMargin(std::ostream const &os):
  This member returns the current right margin setting of the OFoldStream object passed to it as its argument. The member's parameter is down cast in the same way as leftMargin()'s argument: an FBB::Exception exception is thrown if that cast fails.

## EXAMPLE

    #include <iostream>
    #include <string>
    #include <bobcat/ofoldstream>

    using namespace std;
    using namespace FBB;

    void margins(ostream &out)
    {
        cout << OFoldStream::leftMargin(out) << ", " <<
                OFoldStream::rightMargin(out) << endl;
    }

    int main()
    {
        OFoldStream out(cout, 4, 40);

        out << lm(4);

        string line;
        while (getline(cin, line))
            out << line << '\n';

        margins(out);
    }

## FILES

bobcat/ofoldstream - defines the class interface

## SEE ALSO

bobcat(7), lm(3bobcat), mlm(3bobcat), ofoldbuf(3bobcat)

## 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).