transfer::data::source(3tclData transfer facilitietransfer::data::source(3tcl)
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NAME
transfer::data::source - Data source
SYNOPSIS
package require Tcl 8.4
package require snit ?1.0?
package require transfer::copy ?0.2?
package require transfer::data::source ?0.2?
transfer::data::source objectName ?options...?
objectName method ?arg arg ...?
objectName destroy
objectName type
objectName data
objectName size
objectName valid msgvar
objectName transmit channel blocksize done
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DESCRIPTION
This package provides objects mainly describing the origin of some data
to transfer. They are also able to initiate transfers of the described
information to a channel using the foundation package transfer::copy.
API
PACKAGE COMMANDS
transfer::data::source objectName ?options...?
This command creates a new data source object with an associated
Tcl command whose name is objectName. This object command is
explained in full detail in the sections Object command and Ob-
ject methods. The set of supported options is explained in sec-
tion 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::data::source command have the
following general form:
objectName method ?arg arg ...?
The method method and its arg'uments determine the exact behav-
ior of the command. See section Object methods for the detailed
specifications.
OBJECT METHODS
objectName destroy
This method destroys the object. Doing so while a transfer ini-
tiated by the object is active is safe as all data required for
the transfer itself was copied, and the completion of the trans-
fer will not try to access the initiating object anymore. i.e.
the transfer is completely separate from the source object it-
self.
objectName type
This method returns a string describing the type of the data the
object is refering to. The possible values and their meanings
are:
undefined
No data was specified at all, or it was specified incom-
pletely. The object does not know the type.
string The data to transfer is contained in a string.
channel
The data to transfer is contained in a channel.
objectName data
This method returns a value depending on the type of the data
the object refers to, through which the data can be accessed.
The method throws an error if the type is undefined. For type
string the returned result is the data itself, whereas for type
channel the returned result is the handle of the channel con-
taining the data.
objectName size
This method returns a value depending on the type of the data
the object refers to, the size of the data. The method throws
an error if the type is undefined. Return of a negative value
signals that the object is unable to determine an absolute size
upfront (like for data in a channel).
objectName valid msgvar
This method checks the configuration of the object for validity.
It returns a boolean flag as result, whose value is True if the
object is valid, and False otherwise. In the latter case the
variable whose name is stored in msgvar is set to an error mes-
sage describing the problem found with the configuration. Other-
wise this variable is not touched.
objectName transmit channel blocksize done
This method initiates a transfer of the referenced data to the
specified channel. When the transfer completes the command pre-
fix done is invoked, per the rules for the option -command of
command transfer::copy::do in the package transfer::copy. The
blocksize specifies the size of the chunks to transfer in one
go. See the option -blocksize of command transfer::copy::do in
the package transfer::copy.
OPTIONS
All data sources support the options listed below. It should be noted
that the first four options are semi-exclusive, each specifying a dif-
ferent type of data source and associated content. If these options are
specified more than once then the last option specified is used to ac-
tually configure the object.
-string text
This option specifies that the source of the data is an immedi-
ate string, and its associated argument contains the string in
question.
-channel handle
This option specifies that the source of the data is a channel,
and its associated argument is the handle of the channel con-
taining the data.
-file path
This option specifies that the source of the data is a file, and
its associated argument is the path of the file containing the
data.
-variable varname
This option specifies that the source of the data is a string
stored in a variable, and its associated argument contains the
name of the variable in question. The variable is assumed to be
global or namespaced, anchored at the global namespace.
-size int
This option specifies the size of the data transfer. It is op-
tional and defaults to -1. This value, and any other value less
than zero signals to transfer all the data from the source.
-progress command
This option, if specified, defines a command to be invoked for
each chunk of bytes transmitted, allowing the user to monitor
the progress of the transmission of the data. The callback is
always invoked with one additional argument, the number of bytes
transmitted so far.
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 Trackers [http://core.tcl.tk/tcllib/reportlist]. Please
also report any ideas for enhancements you may have for either package
and/or documentation.
When proposing code changes, please provide unified diffs, i.e the out-
put of diff -u.
Note further that attachments are strongly preferred over inlined
patches. Attachments can be made by going to the Edit form of the
ticket immediately after its creation, and then using the left-most
button in the secondary navigation bar.
KEYWORDS
channel, copy, data source, transfer
CATEGORY
Transfer module
COPYRIGHT
Copyright (c) 2006-2009 Andreas Kupries <andreas_kupries@users.sourceforge.net>
tcllib 0.2 transfer::data::source(3tcl)