NAME

       memchan - Create and manipulate memory channels

SYNOPSIS

       package require Tcl

       package require memchan

       memchan ?-initial-size len?

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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>