NAME¶
memchan - Create and manipulate memory channels
SYNOPSIS¶
package require
Tcl
package require
memchan
memchan ?-initial-size
len?
DESCRIPTION¶
This manpage documents both the overall package and the command
memchan.
The package itself provides a number of in-memory channels which can utilized
to
- •
- 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.
COMMAND¶
- 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
interpreters.
Memory channels created by
memchan provide two read-only options which
can be queried via the standard
fconfigure command. These are
- -length
- The value of this option is the number of bytes currently
stored in the queried memory channel.
- -allocated
- 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 -length.
As the channels generated by
memchan 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 and the seek
location is not and the end of the channel. Under these conditions a readable
fileevent-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.
SEE ALSO¶
fifo, fifo2, null, random, zero
KEYWORDS¶
channel, chunk, i/o, in-memory channel, memchan
COPYRIGHT¶
Copyright (c) 1996-2003 Andreas Kupries <andreas_kupries@users.sourceforge.net>
