IO::BufferedSelect (3pm)

    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";
        }
    }

The \*(C`select\*(C' system call (and the \*(C`IO::Select\*(C' 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 \*(C`sysread\*(C' and \*(C`syswrite\*(C' rather than Perl's buffered I/O functions. In the case of reading, there are two issues with combining \*(C`select\*(C' with \*(C`readline\*(C': (1) \*(C`select\*(C' might block but the data we want is already in Perl's input buffer, ready to be slurped in by \*(C`readline\*(C'; and (2) \*(C`select\*(C' might indicate that data is available, but \*(C`readline\*(C' will block because there isn't a full $/-terminated line available.

The purpose of this module is to implement a buffered version of the \*(C`select\*(C' interface that operates on lines, rather than characters. Given a set of filehandles, it will block until a full line is available on one or more of them.

Note that this module is currently limited, in that (1) it only does \*(C`select\*(C' for readability, not writability or exceptions; and (2) it does not support arbitrary line separators ($/): lines must be delimited by newlines.

new ( \s-1HANDLES\s0 )

Create a \*(C`BufferedSelect\*(C' object for a set of filehandles. Note that because this class buffers input from these filehandles internally, you should only use the \*(C`BufferedSelect\*(C' object for reading from them (you shouldn't read from them directly or pass them to other BufferedSelect instances).

read_line

read_line ($timeout)

Block until a line is available on one of the filehandles. If $timeout is \*(C`undef\*(C', it blocks indefinitely; otherwise, it returns after at most $timeout seconds. If @handles is specified, then only these filehandles will be considered; otherwise, it will use all filehandles passed to the constructor. Returns a list of pairs \*(C`[$fh, $line]\*(C', where $fh is a filehandle and $line is the line that was read (including the newline, ala \*(C`readline\*(C'). If the filehandle reached \s-1EOF\s0, then $line will be undef. Note that \*(L"reached \s-1EOF\s0\*(R" is to be interpreted in the buffered sense: if a filehandle is at \s-1EOF\s0 but there are newline-terminated lines in \*(C`BufferedSelect\*(C''s buffer, \*(C`read_line\*(C' will continue to return lines until the buffer is empty.

IO::Select

Antal Novak, <[email protected]>

Copyright (C) 2007 by Antal Novak

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.