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memchan(3tcl) memchan(3tcl) 





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



  

  
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



  

  
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
      -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>








  

    2.2
    Memory channels