noble (3) readlinehistory.3bobcat.gz
NAME
FBB::ReadLineHistory - std::streambuf offering line-editing and history
SYNOPSIS
#include <bobcat/readlinebuf>
Linking option: -lbobcat -lreadline
DESCRIPTION
The FBB::ReadLineHistory object offers access to the history maintained by FBB::ReadLineBuf and
ReadLineStream objects.
The latter two classes use Gnu’s readline library to allow editing of input lines. The accumulated
history of these objects can be accessed from the ReadLineHistory object.
Since Gnu’s readline library maintains global data there can only be one history. The ReadLineHistory
class is therefore, like ReadLineBuf a singleton. (Gnu’s readline library does, however, offer functions
allowing programs to use multiple histories. So it would in principle be possible to design a
non-singleton ReadLineHistory class. Since programs normally only interact with a single terminal, there
is probably little use for non-singleton ReadLineHistory class).
The ReadLineHistory class encapsulates history access. It offers limited facilities: either forward or
backward iterations over the history are offered as well as reading and writing the history from/to
streams. When reading the history from a stream it replaces the currently available lines in Gnu’s
readline history. The content of the history lines and --if defined-- the timestamps of the lines in the
history can be obtained using iterators defined by ReadLineHistory.
NAMESPACE
FBB
All constructors, members, operators and manipulators, mentioned in this man-page, are defined in the
namespace FBB.
INHERITS FROM
-
NESTED TYPES
The class ReadLineHistory defines the following nested types:
HistoryElement
The iterators made available by the ReadLineHistory object provide access to a HistoryElement object.
These objects can be copied and assigned to each other, but user programs cannot otherwise construct
HistoryElement objects.
The class HistoryElement has but two members:
o char const *line() const returns the content of the history line to which a ReadLineHistory
iterator refers;
o char const *timestamp() const returns the timestamp (if defined) of the history line to which a
ReadLineHistory iterator refers;
const_iterator and const_reverse_iterator
The iterators returned by members of the class ReadLineHistory are input iterators, pointing to
HistoryElement objects. As they are input iterators modification of the history elements to which they
refer is not allowed.
The class const_iterator allows iterations from the first to the last history element, the class
const_reverse_iterator allows iterations from the last back to the first history element.
The iterators can be incremented, compared for (in)equality and offer operator* and operator-> members,
offering access to, respectively, HistoryElement objects and their addresses.
CONSTRUCTORS
As the class ReadLineHistory is a singleton class, there are no publicly available constructors, nor are
assignment operators available.
STATIC MEMBER FUNCTIONS
o ReadLineHistory &instance():
A reference to the ReadLineHistory object is returned. If any history has been accumulated it can
immediately be retrieved. Using this static member will not affect the way the ReadLineHistory
object handles timestamps when saving or retrieving history lines. When initially constructed the
ReadLineHistory object assumes that timestamps are not used.
o ReadLineHistory &instance(bool useTimestamps):
A reference to the ReadLineHistory object is returned. If any history has been accumulated it can
immediately be retrieved. The useTimestamps parameter defines the way history lines are read from
or written to a stream. When specifying true the history inserted into a stream will include
timestamps (which may be empty if no timestamps were recorded). Likewise, when extracting the
history timestamps are extracted too (which may also be empty). When specifying false no
timestamps are read or written. A mismatch between the actual content of the stream from which the
history is extracted and the useTimestamps parameter will results in unexpected behavior.
MEMBER FUNCTIONS
o ReadLineHistory::const_iterator begin() const:
An input iterator pointing to the first history line is returned.
o ReadLineHistory::const_iterator end() const:
An input iterator pointing beyond the last history line is returned.
o size_t maxSize() const:
The maximum number of lines that can be stored in the history is returned. After collecting a
history of maxSize lines, the next line entered will cause the initial history line to be removed
from the history, making room for the next line to be added at the end of the history.
o ReadLineHistory::const_reverse_iterator rbegin() const:
An input iterator pointing to the last history line is returned. Incrementing this iterator will
access the previous line in the history.
o ReadLineHistory::const_reverse_iterator rend() const:
An input iterator pointing before the first history line is returned.
o ReadLineHistory &setTimestamps(bool useTimestamps):
xThe current status of the timestamps usage is set according to the value of its parameter. When
true inserting and extracting history will include the timestamps. No timestamps are inserted or
extracted when false. It returns a reference to the updated ReadLineHistory object, allowing
constructions like (assuming the availability of ReadLineHistory &history):
cout << history.setTimestamps(true);
o size_t size() const:
The number of lines currently stored in the history is returned.
o bool timestamps() const:
The current status of the timestamps usage is returned. When returning true inserting and
extracting history will include the timestamps. No timestamps are inserted or extracted when this
member returns false
OVERLOADED OPERATORS
o std::istream &operator>>(std::istream &in, ReadLineHistory &his):
The history available at the in stream is extracted to become the current history, replacing the
existing (Gnu readline) history by the history read from in. The useTimestamp status determines
whether timestams are extracted (if true) or not (if false). If extracting the history from in
fails an exception is thrown.
o std::ostream &operator<<(std::ostream &out, ReadLineHistory &his):
The current history is written to the out stream. The useTimestamp status determines whether
timestams are inserted (if true) or not (if false).
EXAMPLE
#include <iostream>
#include <algorithm>
#include <fstream>
#include <bobcat/datetime>
#include <bobcat/readlinestream>
//#include <bobcat/readlinehistory>
#include "../readlinehistory"
using namespace std;
using namespace FBB;
void showHis(ReadLineHistory::HistoryElement const &element)
{
cout << element.timestamp() << " " << element.line() << ’\n’;
}
string timestamp()
{
return DateTime().rfc2822();
};
int main(int argc, char **argv)
{
ReadLineStream in("? ", ReadLineBuf::EXPAND_HISTORY);
in.useTimestamps(×tamp);
cout << "Enter some lines, end the input using ctrl-d\n";
string line;
while (getline(in, line))
;
// argument means: write/read
// history timestamps
ReadLineHistory &history = ReadLineHistory::instance(argc > 1);
cout << "All lines, from the first to the last:\n";
for_each(history.begin(), history.end(), showHis);
cout << "\n"
"Again: all lines, from the first to the last:\n";
for_each(history.begin(), history.end(), showHis);
cout << "\n"
"All lines, from the last to the first:\n";
for_each(history.rbegin(), history.rend(), showHis);
cout << "\n"
"History out and in:\n"
"\n";
ofstream hisout("history.out");
hisout << history;
hisout.close();
ifstream hisin("history.out");
hisin >> history;
cout << "All lines, from the first to the last:\n";
for_each(history.begin(), history.end(), showHis);
cout << "\n"
"All lines, from the last to the first:\n";
for_each(history.rbegin(), history.rend(), showHis);
}
FILES
bobcat/readlinehistory - defines the class interface
SEE ALSO
bobcat(7), readline(3), readlinebuf(3), readlinestream(3)
BUGS
None Reported.
BOBCAT PROJECT FILES
o https://fbb-git.gitlab.io/bobcat/: gitlab project page;
o bobcat_6.04.00-x.dsc: detached signature;
o bobcat_6.04.00-x.tar.gz: source archive;
o bobcat_6.04.00-x_i386.changes: change log;
o libbobcat1_6.04.00-x_*.deb: debian package containing the libraries;
o libbobcat1-dev_6.04.00-x_*.deb: debian package containing the libraries, headers and manual pages;
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).