DragonFly On-Line Manual Pages

memchan(n)                                                          memchan(n)

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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

       o      capture stream-like information in a natural way instead of
              using set and append to manipulate strings

       o      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>

Memory channels                       2.2                           memchan(n)