fifo - Create and manipulate u-turn fifo channels
package require Tcl
package require memchan
- creates a stream-oriented in-memory channel and returns its handle. There
is no restriction on the ultimate size of the channel, it will always grow
as much as is necessary to accommodate the data written into it.
In contrast to the channels generated by memchan a channel created
here effectively represents an U-turn. All data written into it can be
read out, but only in the same order. This also means that a fifo channel
is not seekable.
The channels created here can be transferred between interpreters in the
same thread and between threads, but only as a whole. It is not possible
to use them to create a bi- or unidirectional connection between two
Memory channels created by fifo
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 stored in the
queried memory channel.
- The value of this option is the number of bytes currently allocated by the
queried memory channel. This number is at least as big as the value of
As the channels generated by fifo
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.
One possible application of memory channels created by memchan
is as temporary storage device to collect data coming in over a
pipe or a socket. If part of the processing of the incoming data is to read
and process header bytes or similar fifo are easier to use as they do not
require seeking back and forth to switch between the assimilation of headers
at the beginning and writing new data at the end.
fifo2, memchan, null
channel, fifo, i/o, in-memory channel, memchan, stream
Copyright (c) 1996-2003 Andreas Kupries <email@example.com>