NAME

       fifo2 - Create and manipulate pipe fifo channels

SYNOPSIS

       package require Tcl

       package require memchan

       fifo2

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>