rs_ecc(n) rs_ecc(n) 







rs_ecc - Reed-Solomon error correcting code








package require Tcl ?8.2?


package require Trf ?2.1.4?


rs_ecc ?options...? ?data?












The command rs_ecc provides a reed-solomon error correcting
    coder. The coder operates on blocks of 248 bytes each, therefore buffering
    247 bytes.



  

  







  

  
This option has to be present and is always understood.
    
For immediate mode the argument value specifies the
        operation to use. For an attached encoding it specifies the
        operation to use for writing. Reading will automatically use the
        reverse operation. See section IMMEDIATE versus ATTACHED for
        explanations of these two terms.

    
Beyond the argument values listed above all unique
        abbreviations are recognized too.

    
Encode converts from arbitrary (most likely binary)
        data into a representation containing additional error correcting
        information, decode does the reverse, and performs the error
        correction if necessary.

  

  

  
The presence/absence of this option determines the main operation mode of
      the transformation.
    
If present the transformation will be stacked onto the
        channel whose handle was given to the option and run in
        attached mode. More about this in section IMMEDIATE versus
        ATTACHED.

    
If the option is absent the transformation is used in
        immediate mode and the options listed below are recognized. More
        about this in section IMMEDIATE versus ATTACHED.

  

  

  
This options is legal if and only if the transformation is used in
      immediate mode. It provides the handle of the channel the data to
      transform has to be read from.
    
If the transformation is in immediate mode and this
        option is absent the data to transform is expected as the last argument
        to the transformation.

  

  

  
This options is legal if and only if the transformation is used in
      immediate mode. It provides the handle of the channel the generated
      transformation result is written to.
    
If the transformation is in immediate mode and this
        option is absent the generated data is returned as the result of the
        command itself.

  












The transformation distinguishes between two main ways of using
    it. These are the immediate and attached operation modes.


For the attached mode the option -attach is used to
    associate the transformation with an existing channel. During the execution
    of the command no transformation is performed, instead the channel is
    changed in such a way, that from then on all data written to or read from it
    passes through the transformation and is modified by it according to the
    definition above. This attachment can be revoked by executing the command
    unstack for the chosen channel. This is the only way to do this at
    the Tcl level.


In the second mode, which can be detected by the absence of option
    -attach, the transformation immediately takes data from either its
    commandline or a channel, transforms it, and returns the result either as
    result of the command, or writes it into a channel. The mode is named after
    the immediate nature of its execution.


Where the data is taken from, and delivered to, is governed by the
    presence and absence of the options -in and -out. It should be
    noted that this ability to immediately read from and/or write to a channel
    is an historic artifact which was introduced at the beginning of Trf's life
    when Tcl version 7.6 was current as this and earlier versions have trouble
    to deal with \0 characters embedded into either input or output.








trf-intro








error correction, reed-solomon








Copyright (c) 1996-2003, Andreas Kupries <andreas_kupries@users.sourceforge.net>








  

    2.1.4
    Trf transformer commands