'\"
'\" Generated from file 'tqueue\&.man' by tcllib/doctools with format 'nroff'
'\" Copyright (c) 2006 Andreas Kupries <andreas_kupries@users\&.sourceforge\&.net>
'\"
.TH "transfer::copy::queue" n 0\&.2 tcllib "Data transfer facilities"
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.SH NAME
transfer::copy::queue \- Queued transfers
.SH SYNOPSIS
package require \fBTcl 8\&.5 9\fR
.sp
package require \fBsnit ?1\&.0?\fR
.sp
package require \fBstruct::queue ?1\&.4?\fR
.sp
package require \fBtransfer::copy ?0\&.3?\fR
.sp
package require \fBtransfer::copy::queue ?0\&.2?\fR
.sp
\fBtransfer::copy::queue\fR \fIobjectName\fR \fIoutchannel\fR ?\fIoptions\fR\&.\&.\&.?
.sp
\fIobjectName\fR \fBmethod\fR ?\fIarg arg \&.\&.\&.\fR?
.sp
\fIobjectName\fR \fBdestroy\fR
.sp
\fIobjectName\fR \fBbusy\fR
.sp
\fIobjectName\fR \fBpending\fR
.sp
\fIobjectName\fR \fBput\fR \fIrequest\fR
.sp
.BE
.SH DESCRIPTION
.PP
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\&.
.PP
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\&.
.PP
\fINOTE\fR:
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\&.
.PP
All transfer requests are of the form
.PP
.CS


	{type data options\&.\&.\&.}

.CE
.PP
where \fItype\fR is in {\fBchan\fR, \fBstring\fR}, and \fIdata\fR
specifies the information to transfer\&.
For \fBchan\fR the data is the handle of the channel containing the
actual information to transfer, whereas for \fBstring\fR \fIdata\fR
contains directly the information to transfer\&.
The \fIoptions\fR are a list of them and their values, and are the
same as are accepted by the low-level copy operations of the package
\fBtransfer::copy\fR\&.
Note how just prepending the request with \fBtransfer::copy::do\fR and
inserting a channel handle in between \fIdata\fR and \fIoptions\fR
easily transforms it from a pure data structure into a command whose
evaluation will perform the request\&.
.SH API
.SS "PACKAGE COMMANDS"
.TP
\fBtransfer::copy::queue\fR \fIobjectName\fR \fIoutchannel\fR ?\fIoptions\fR\&.\&.\&.?
This command creates a new queue object for the management of the
channel \fIoutchannel\fR, with an associated Tcl command whose name is
\fIobjectName\fR\&.
This \fIobject\fR command is explained in full detail in the sections
\fBObject command\fR and \fBObject methods\fR\&. The set of
supported \fIoptions\fR is explained in section \fBOptions\fR\&.
.sp
The object command will be created under the current namespace if the
\fIobjectName\fR 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\&.
.PP
.SS "OBJECT COMMAND"
All objects created by the \fB::transfer::copy::queue\fR command have
the following general form:
.TP
\fIobjectName\fR \fBmethod\fR ?\fIarg arg \&.\&.\&.\fR?
The method \fBmethod\fR and its \fIarg\fR'uments determine the
exact behavior of the command\&.
See section \fBObject methods\fR for the detailed
specifications\&.
.PP
.SS "OBJECT METHODS"
.TP
\fIobjectName\fR \fBdestroy\fR
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\&.
.TP
\fIobjectName\fR \fBbusy\fR
This method returns a boolean value telling us if the object is
currently serving a request (i\&.e\&. \fIbusy\fR, value \fBTrue\fR), or
not (i\&.e\&. \fIidle\fR, value \fBFalse\fR)\&.
.TP
\fIobjectName\fR \fBpending\fR
This method returns the number of requests currently waiting in the
queue for their execution\&. A request currently served is not counted
as waiting\&.
.TP
\fIobjectName\fR \fBput\fR \fIrequest\fR
This method enters the transfer \fIrequest\fR into the object's queue
of waiting requests\&.
If the object is \fIidle\fR it will become \fIbusy\fR, immediately
servicing the request\&. Otherwise servicing the new request will be
defered until all preceding requests have been served\&.
.PP
.SH OPTIONS
The only option known is \fB-on-status-change\fR\&. 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
\fBpending\fR and \fBbusy\fR, in this order\&. This allows any
user to easily know, for example, when the object has processed all
outstanding requests\&.
.SH 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\&.
.PP
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\&.
.SH "BUGS, IDEAS, FEEDBACK"
This document, and the package it describes, will undoubtedly contain
bugs and other problems\&.
Please report such in the category \fItransfer\fR of the
\fITcllib Trackers\fR [http://core\&.tcl\&.tk/tcllib/reportlist]\&.
Please also report any ideas for enhancements you may have for either
package and/or documentation\&.
.PP
When proposing code changes, please provide \fIunified diffs\fR,
i\&.e the output of \fBdiff -u\fR\&.
.PP
Note further that \fIattachments\fR are strongly preferred over
inlined patches\&. Attachments can be made by going to the \fBEdit\fR
form of the ticket immediately after its creation, and then using the
left-most button in the secondary navigation bar\&.
.SH KEYWORDS
channel, copy, queue, transfer
.SH CATEGORY
Transfer module
.SH COPYRIGHT
.nf
Copyright (c) 2006 Andreas Kupries <andreas_kupries@users\&.sourceforge\&.net>

.fi
