[comment {-*- tcl -*- doctools manpage}]
[manpage_begin transfer::data::source n 0.2]
[keywords channel]
[keywords copy]
[keywords {data source}]
[keywords transfer]
[copyright {2006-2009 Andreas Kupries <andreas_kupries@users.sourceforge.net>}]
[moddesc   {Data transfer facilities}]
[titledesc {Data source}]
[category  {Transfer module}]
[require Tcl                    8.4]
[require snit                   [opt 1.0]]
[require transfer::copy         [opt 0.2]]
[require transfer::data::source [opt 0.2]]
[description]
[para]

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
[package transfer::copy].

[section API]
[subsection {Package commands}]

[list_begin definitions]

[call [cmd transfer::data::source] \
	[arg objectName] \
	[opt [arg options]...]]

This command creates a new data source object with an associated Tcl
command whose name is [arg objectName].

This [term object] command is explained in full detail in the sections
[sectref {Object command}] and [sectref {Object methods}]. The set of
supported [arg options] is explained in section [sectref {Options}].

[para]

The object command will be created under the current namespace if the
[arg 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.

[list_end]

[subsection {Object command}]

All objects created by the [cmd ::transfer::data::source] command have
the following general form:

[list_begin definitions]

[call [arg objectName] [method method] [opt [arg "arg arg ..."]]]

The method [method method] and its [arg arg]'uments determine the
exact behavior of the command.

See section [sectref {Object methods}] for the detailed
specifications.

[list_end]

[subsection {Object methods}]

[list_begin definitions]

[call [arg objectName] [method 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 transfer is completely
separate from the source object itself.

[call [arg objectName] [method type]]

This method returns a string describing the type of the data the
object is refering to. The possible values and their meanings are:

[list_begin definitions]
[def [const undefined]]
No data was specified at all, or it was specified incompletely. The
object does not know the type.

[def [const string]]
The data to transfer is contained in a string.

[def [const channel]]
The data to transfer is contained in a channel.

[list_end]

[call [arg objectName] [method 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 [const undefined]. For type
[const string] the returned result is the data itself, whereas for
type [const channel] the returned result is the handle of the channel
containing the data.

[call [arg objectName] [method 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 [const undefined]. Return of
a negative value signals that the object is unable to determine an
absolute size upfront (like for data in a channel).

[call [arg objectName] [method valid] [arg msgvar]]

This method checks the configuration of the object for validity. It
returns a boolean flag as result, whose value is [const True] if the
object is valid, and [const False] otherwise. In the latter case the
variable whose name is stored in [arg msgvar] is set to an error
message describing the problem found with the configuration. Otherwise
this variable is not touched.

[call [arg objectName] [method transmit] [arg channel] [arg blocksize] [arg done]]

This method initiates a transfer of the referenced data to the
specified [arg channel].

When the transfer completes the command prefix [arg done] is invoked,
per the rules for the option [option -command] of command
[cmd transfer::copy::do] in the package [package transfer::copy].

The [arg blocksize] specifies the size of the chunks to transfer in
one go. See the option [option -blocksize] of command
[cmd transfer::copy::do] in the package [package transfer::copy].

[list_end]

[subsection 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.

[list_begin options]
[include include/dsource_options.inc]
[list_end]

[vset CATEGORY transfer]
[include ../common-text/feedback.inc]
[manpage_end]
