Version 10 of memchan

Updated 2007-01-28 13:49:24

This package is currently hosted on SourceForge [L1 ]. Its homepage is http://memchan.sourceforge.net/ This package is part of the ActiveTcl Batteries Included distribution.

It provides several new channel types whose instances store the transfered information in memory and do not go to the OS at all.

Channel types

  • memchan Read and write a memory buffer via a channel.
  • fifo A fifo buffer presented as a channel
  • fifo2 Creates a pair of channels with a fifo connecting them
  • null Like the unix null device, discards everything and returns eof on read.
  • zero Like the unix zero device. Discards all writes and reads return all zeros.
  • random Like the unix random device. Writing seeds an ISAAC pseudo-random number generator. Reading returns random bytes from the generator.
 What: memchan
 Where: http://memchan.sourceforge.net/ >
        http://www.purl.org/NET/akupries/soft/memchan/
 Description: A new channel type for Tcl 8's channel system.  Memory channels
        conform to the same interface as files and sockets, but the data
        is stored in memory rather than in files.  They are good for
        long dynamic strings and passing large quantities of data.
        Supports Window and Unix.  See the web page for pointers to the
        source and binary downloads.
        Currently at version 2.2.1
 Updated: 03-Dec-2004
 Contact: mailto:[email protected] (Andreas Kupries)
          mailto:[email protected] (Pat Thoyts)

LES on Sep 12 2005: Would it be possible for memchan or a similar hypothetical extension to store data in memory in such a way that it survives the exit command and thus remains available to other Tcl programs or subsequent calls of the same program?

TP Sep 12 2005: Maybe not with memchan, but look into shared-memory and Inventory of IPC methods for SysV IPC shared memory extensions, which can survive after process exit (but not reboot). Also, Tequila and Tuplespace for Tcl solutions that would require another running Tcl process to hold the data.

On Linux, Solaris, and probably other POSIX OS's, it is as simple as using /dev/shm as a directory to read/write files into a memory-backed filesystem:

 # first process
 set fd [open /dev/shm/yourfile w]
 puts $fd $yourstuff
 close $fd
 exit

 # next process
 set fd [open /dev/shm/yourfile]
 set yourstuff [read $fd]
 close $fd

Check that you have proper permissions to create files in /dev/shm.

I'm not quite sure what Windows equivalents there are.

Extensions for Tcl and Tk links to many more interesting extensions to Tcl.

Andreas Kupries

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