Ubuntu Manpage: transfer::copy::queue

NAME

       transfer::copy::queue - Queued transfers

SYNOPSIS

       package require Tcl  8.4

       package require snit  ?1.0?

       package require struct::queue  ?1.4?

       package require transfer::copy  ?0.2?

       package require transfer::copy::queue  ?0.1?

       transfer::copy::queue objectName outchannel ?options...?

       objectName method ?arg arg ...?

       objectName destroy

       objectName busy

       objectName pending

       objectName put request

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DESCRIPTION

       This  package  provides objects which serialize transfer requests for a single channel by means of a fifo
       queue. Accumulated requests are executed in order of entrance, with the first request  reaching  an  idle
       object  starting  the  execution in general. New requests can be added while the object is active and are
       defered until all requests entered before them have been completed successfully.

       When a request causes a transfer error execution stops and all requests coming after it are  not  served.
       Currently this means that their completion callbacks are never triggered at all.

       NOTE:  Not  triggering  the  completion callbacks of the unserved requests after an error stops the queue
       object is something I am not fully sure that it makes sense. It forces the user of the queue to  remember
       the callbacks as well and run them. Because otherwise everything in the system which depends on getting a
       notification about the status of a request will hang in the air. I am slowly convincing myself that it is
       more  sensible  to trigger the relevant completion callbacks with an error message about the queue abort,
       and 0 bytes transfered.

       All transfer requests are of the form

              {type data options...}

       where type is in {chan, string}, and data specifies the information to transfer.  For chan  the  data  is
       the handle of the channel containing the actual information to transfer, whereas for string data contains
       directly the information to transfer.  The options are a list of them and their values, and are the  same
       as are accepted by the low-level copy operations of the package transfer::copy.  Note how just prepending
       the request with transfer::copy::do and inserting a channel handle in between  data  and  options  easily
       transforms it from a pure data structure into a command whose evaluation will perform the request.

API

PACKAGE COMMANDS
transfer::copy::queue objectName outchannel ?options...?
This command creates a new queue object for the management of the channel outchannel, with an
associated Tcl command whose name is objectName. This object command is explained in full detail
in the sections Object command and Object methods. The set of supported options is explained in
section Options.

The object command will be created under the current namespace if the objectName is not fully
qualified, and in the specified namespace otherwise. The fully qualified name of the object
command is returned as the result of the command.

OBJECT COMMAND
All objects created by the ::transfer::copy::queue command have the following general form:

objectName method ?arg arg ...?
The method method and its arg'uments determine the exact behavior of the command. See section
Object methods for the detailed specifications.

OBJECT METHODS
objectName destroy
This method destroys the object. Doing so while the object is busy will cause errors later on,
when the currently executed request completes and tries to access the now missing data structures
of the destroyed object.

objectName busy
This method returns a boolean value telling us if the object is currently serving a request (i.e.
busy, value True), or not (i.e. idle, value False).

objectName pending
This method returns the number of requests currently waiting in the queue for their execution. A
request currently served is not counted as waiting.

objectName put request
This method enters the transfer request into the object's queue of waiting requests. If the
object is idle it will become busy, immediately servicing the request. Otherwise servicing the new
request will be defered until all preceding requests have been served.

OPTIONS

       The  only option known is -on-status-change. It is optional and defaults to the empty list, disabling the
       reporting of status changes. Otherwise its argument is a command prefix which  is  invoked  whenever  the
       internal  status of the object changed. The callback is invoked with two additional arguments, the result
       of the methods pending and busy, in this order. This allows any user to easily know,  for  example,  when
       the object has processed all outstanding requests.

USE

       A  possible  application  of  this  package  and  class is within a HTTP 1.1 server, managing the results
       waiting for transfer to the client.

       It should be noted that in this application the system also needs  an  additional  data  structure  which
       keeps  track of outstanding results as they may come back in a different order than the requests from the
       client, and releases them to the actual queue in the proper order.

BUGS, IDEAS, FEEDBACK

       This document, and the package it describes, will undoubtedly contain bugs and  other  problems.   Please
       report      such      in      the     category     transfer     of     the     Tcllib     SF     Trackers
       [http://sourceforge.net/tracker/?group_id=12883].  Please also report any ideas for enhancements you  may
       have for either package and/or documentation.

KEYWORDS

       channel, copy, queue, transfer

COPYRIGHT

       Copyright (c) 2006 Andreas Kupries <andreas_kupries@users.sourceforge.net>