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.\" ========================================================================
.\"
.IX Title "IO::BufferedSelect 3pm"
.TH IO::BufferedSelect 3pm "2022-11-20" "perl v5.36.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
IO::BufferedSelect \- Line\-buffered select interface
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 12
\&    use IO::BufferedSelect;
\&    my $bs = new BufferedSelect($fh1, $fh2);
\&    while(1)
\&    {
\&        my @ready = $bs\->read_line();
\&        foreach(@ready)
\&        {
\&            my ($fh, $line) = @$_;
\&            my $fh_name = ($fh == $fh1 ? "fh1" : "fh2");
\&            print "$fh_name: $line";
\&        }
\&    }
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The \f(CW\*(C`select\*(C'\fR system call (and the \f(CW\*(C`IO::Select\*(C'\fR interface) allows us to process
multiple streams simultaneously, blocking until one or more of them is ready for
reading or writing.  Unfortunately, this requires us to use \f(CW\*(C`sysread\*(C'\fR and
\&\f(CW\*(C`syswrite\*(C'\fR rather than Perl's buffered I/O functions.  In the case of reading,
there are two issues with combining \f(CW\*(C`select\*(C'\fR with \f(CW\*(C`readline\*(C'\fR: (1) \f(CW\*(C`select\*(C'\fR
might block but the data we want is already in Perl's input buffer, ready to
be slurped in by \f(CW\*(C`readline\*(C'\fR; and (2) \f(CW\*(C`select\*(C'\fR might indicate that data is
available, but \f(CW\*(C`readline\*(C'\fR will block because there isn't a full
\&\f(CW$/\fR\-terminated line available.
.PP
The purpose of this module is to implement a buffered version of the \f(CW\*(C`select\*(C'\fR
interface that operates on \fIlines\fR, rather than characters.  Given a set of
filehandles, it will block until a full line is available on one or more of
them.
.PP
Note that this module is currently limited, in that (1) it only does \f(CW\*(C`select\*(C'\fR
for readability, not writability or exceptions; and (2) it does not support
arbitrary line separators (\f(CW$/\fR): lines must be delimited by newlines.
.SH "CONSTRUCTOR"
.IX Header "CONSTRUCTOR"
.IP "new ( \s-1HANDLES\s0 )" 4
.IX Item "new ( HANDLES )"
Create a \f(CW\*(C`BufferedSelect\*(C'\fR object for a set of filehandles.  Note that because
this class buffers input from these filehandles internally, you should \fBonly\fR
use the \f(CW\*(C`BufferedSelect\*(C'\fR object for reading from them (you shouldn't read from
them directly or pass them to other BufferedSelect instances).
.SH "METHODS"
.IX Header "METHODS"
.IP "read_line" 4
.IX Item "read_line"
.PD 0
.IP "read_line ($timeout)" 4
.IX Item "read_line ($timeout)"
.ie n .IP "read_line ($timeout, @handles)" 4
.el .IP "read_line ($timeout, \f(CW@handles\fR)" 4
.IX Item "read_line ($timeout, @handles)"
.PD
Block until a line is available on one of the filehandles.  If \f(CW$timeout\fR is
\&\f(CW\*(C`undef\*(C'\fR, it blocks indefinitely; otherwise, it returns after at most
\&\f(CW$timeout\fR seconds.
.Sp
If \f(CW@handles\fR is specified, then only these filehandles will be considered;
otherwise, it will use all filehandles passed to the constructor.
.Sp
Returns a list of pairs \f(CW\*(C`[$fh, $line]\*(C'\fR, where \f(CW$fh\fR is a filehandle and
\&\f(CW$line\fR is the line that was read (including the newline, ala \f(CW\*(C`readline\*(C'\fR).  If
the filehandle reached \s-1EOF,\s0 then \f(CW$line\fR will be undef.  Note that \*(L"reached
\&\s-1EOF\*(R"\s0 is to be interpreted in the buffered sense: if a filehandle is at \s-1EOF\s0 but
there are newline-terminated lines in \f(CW\*(C`BufferedSelect\*(C'\fR's buffer, \f(CW\*(C`read_line\*(C'\fR
will continue to return lines until the buffer is empty.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
IO::Select
.SH "AUTHOR"
.IX Header "AUTHOR"
Antal Novak, <afn@cpan.org>
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
Copyright (C) 2007 by Antal Novak
.PP
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself, either Perl version 5.8.8 or,
at your option, any later version of Perl 5 you may have available.