transfer::data::source(n) Data transfer facilities transfer::data::source(n)
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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 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 names-
pace 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 behavior of the command. See section Object methods for the detailed spec-
ifications.
OBJECT METHODS
objectName destroy
This method destroys the object. Doing so while a transfer initiated by the object is active is safe as all data required for the
transfer itself was copied, and the completion of the transfer will not try to access the initiating object anymore. i.e. the trans-
fer is completely separate from the source object itself.
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 incompletely. 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 containing 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 message
describing the problem found with the configuration. Otherwise 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 prefix
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
different type of data source and associated content. If these options are specified more than once then the last option specified is used
to actually configure the object.
-string text
This option specifies that the source of the data is an immediate string, and its associated argument contains the string in ques-
tion.
-channel handle
This option specifies that the source of the data is a channel, and its associated argument is the handle of the channel containing
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 optional 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 transmit-
ted 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 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, data source, transfer
CATEGORY
Transfer module
COPYRIGHT
Copyright (c) 2006-2009 Andreas Kupries <andreas_kupries@users.sourceforge.net>
transfer 0.2 transfer::data::source(n)