fifo2 - Create and manipulate pipe fifo channels
package require Tcl
package require memchan
The command described here is only available in a not-yet released version of
the package. Use the CVS to get the sources.
- 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
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
- The value of this option is the number of bytes currently available for
reading from the channel.
- The value of this option is the number of bytes currently written into the
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
The channels are also readable if they contain more than zero bytes. Under this
conditions a readable fileevent
-handler will fire continuously.
fifo, memchan, null
channel, fifo, i/o, in-memory channel, memchan, stream
Copyright (c) 1996-2003 Andreas Kupries <email@example.com>