fifo2(n)                                                              fifo2(n)



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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>




Memory channels                       2.2                             fifo2(n)
