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  ?0.1?

       package require transfer::data::source  ?0.1?

       transfer::data::source object ?options...?

       object destroy

       object type

       object data

       object size

       object valid msgvar

       object 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

       transfer::data::source object ?options...?
	      This command creates and configures a new source object. The fully qualified name of the object command is returned as the result of
	      the command.

	      The  recognized  options are 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 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
		     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 optional and defaults to -1. This value, and any other value less
		     than zero signals to transfer all the data from the source.

       object 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.

       object 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.

       object 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.

       object 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).

       object 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.

       object 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.

KEYWORDS

       channel, copy, data source, transfer

COPYRIGHT

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

transfer								0.1						 transfer::data::source(n)