NAME

       fifo2 - Create and manipulate pipe fifo channels

SYNOPSIS

       package require Tcl

       package require memchan

       fifo2

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DESCRIPTION

       The command described here is only available in a not-yet released version of the package.
       Use the CVS to get the sources.

       fifo2  creates two stream-oriented in-memory channels and returns their handles as a  two-
              element  list.  There  is no restriction on the ultimate size of the channels, they
              will always grow as much as is necessary to accommodate the data written into them.

              In contrast to the channels generated by fifo a pair of channels  created  here  is
              connected  internally  in such a way that data written into one channel can be read
              from the other. All data written into them is read in the  same  order.  This  also
              means that the two channels of the pair are not seekable.

              The  channels  created  here  can  be  transferred between interpreters in the same
              thread and between threads. As  both  channels  in  the  pair  can  be  transferred
              independently  they  can  be  used to create a bidirectional connection between two
              interpreters.

       Memory channels created by fifo2 provide two read-only options which can  be  queried  via
       the standard fconfigure command. These are

       -rlength
              The  value  of  this  option is the number of bytes currently available for reading
              from the channel.

       -wlength
              The value of this option is the number of bytes currently written into the channel.

       Note that the two lengths are switched for the channels of a pair.  In  other  words,  the
       number  of  bytes written for one of the channels is the number of bytes readable from the
       other end.

       As the channels generated by fifo2 grow as necessary they are always writable. This  means
       that a writable fileevent-handler will fire continuously.

       The channels are also readable if they contain more than zero bytes. Under this conditions
       a readable fileevent-handler will fire continuously.

SEE ALSO

       fifo, memchan, null

KEYWORDS

       channel, fifo, i/o, in-memory channel, memchan, stream

COPYRIGHT

       Copyright (c) 1996-2003 Andreas Kupries <andreas_kupries@users.sourceforge.net>