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transfer::data::source - Data source
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 valid msgvar
objectName transmit channel blocksize done
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.
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 namespace otherwise. The fully qualified name of the object command is returned as the result of the command.
All objects created by the ::transfer::data::source command have the following general form:
The method method and its arg'uments determine the exact behavior of the command. See section Object methods for the detailed specifications.
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.
This method returns a string describing the type of the data the object is refering to. The possible values and their meanings are:
No data was specified at all, or it was specified incompletely. The object does not know the type.
The data to transfer is contained in a string.
The data to transfer is contained in a channel.
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.
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).
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.
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.
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.
This option specifies that the source of the data is an immediate string, and its associated argument contains the string in question.
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.
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.
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.
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.
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.
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. 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 output of diff -u.
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Copyright © 2006-2009 Andreas Kupries