---
name: "ofoldstream"
section: "3bobcat"
platform: "linux"
package: "libbobcat-dev"
version: "6.07.01-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/ofoldstream"
---

# ofoldstream(3bobcat)

Folds long lines

## 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)](/ofoldbuf/3bobcat.md) 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:

- o

  **BLANKS**:\
   The default, indicating that the left margin is specified and written as a number of blanks;

- o

  **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)](/ofoldbuf/3bobcat.md)) having two values:

- o

  **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.

- o

  **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

- o

  **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\_BLANKS*for, resp. its left margin, right margin left-margin characters and *TrailingBlanks* handling mode.

-

  - o

  **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.

-

  - o

  **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.

- o

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

-

  - o

  **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.

-

  - o

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

-

  - o

  **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.

-

  - o

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

-

  - o

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

-

  - o

  **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

- o

  **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.

- o

  **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)](/bobcat/7.md),  [**lm**(3bobcat)](/lm/3bobcat.md), [**mlm**(3bobcat)](/mlm/3bobcat.md), [**ofoldbuf**(3bobcat)](/ofoldbuf/3bobcat.md)

## BUGS

None Reported.

## BOBCAT PROJECT FILES

- o

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

Debian Bobcat project files:

- o

  *libbobcat6*: debian package containing the shared library, changelog and copyright note;

- o

  *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**).