memchan - Create and manipulate memory channels
package require Tcl
package require memchan
This manpage documents both the overall package and the command memchan
The package itself provides a number of in-memory channels which can utilized
- capture stream-like information in a natural way instead of using
set and append to manipulate strings
- or to transfer data between interpreters, in the same thread or not.
- memchan ?-initial-size len?
- creates a chunk-oriented in-memory channel and returns its handle. If an
initial size is specified the system will pre-allocate len bytes of
buffer space for the contents. This 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.
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 memchan
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 memchan
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 and the seek
location is not and the end of the channel. Under these conditions a readable
-handler will fire continuously.
Note that writing to such a channel usually occurs at the end, thus suppressing
readable events. This also means that users have to take care to seek
the channel to a location before the end before trying to read data back.
fifo, fifo2, null, random, zero
channel, chunk, i/o, in-memory channel, memchan
Copyright (c) 1996-2003 Andreas Kupries <email@example.com>