rcs(n) RCS low level utilities rcs(n) 







rcs - RCS low level utilities








package require Tcl 8.4


package require rcs ?0.1?


::rcs::text2dict text


::rcs::dict2text dict


::rcs::file2dict filename


::rcs::dict2file filename dict


::rcs::decodeRcsPatch text


::rcs::encodeRcsPatch pcmds


::rcs::applyRcsPatch text pcmds












The Revision Control System, short RCS, is a set of
    applications and related data formats which allow a system to persist the
    history of changes to a text. It, and its relative SCCS are the basis for
    many other such systems, like CVS, etc.


This package does not implement RCS.


It only provides a number of low level commands which should be
    useful in the implementation of any revision management system, namely:



  
[1]

  
The conversion of texts into and out of a data structures which allow the
      easy modification of such text by patches, i.e. sequences of
      instructions for the transformation of one text into an other.

  
[2]

  
And the conversion of one particular format for patches, the so-called
      RCS patches, into and out of data structures which allow their easy
      application to texts.











  
::rcs::text2dict text

  
Converts the argument text into a dictionary containing and
      representing the same text in an indexed form and returns that dictionary
      as its result. More information about the format of the result can be
      found in section TEXT DICT DATA STRUCTURE. This command returns the
      canonical representation of the input.

  
::rcs::dict2text dict

  
This command provides the complementary operation to
      ::rcs::text2dict. It converts a dictionary in the form described in
      section TEXT DICT DATA STRUCTURE back into a text and returns that
      text as its result. The command does accept non-canonical representations
      of the text as its input.

  
::rcs::file2dict filename

  
This command is identical to ::rcs::text2dict, except that it reads
      the text to convert from the file with path filename. The file has
      to exist and must be readable as well.

  
::rcs::dict2file filename dict

  
This command is identical to ::rcs::2dict2text, except that it
      stores the resulting text in the file with path filename. The file
      is created if it did not exist, and must be writable. The result of the
      command is the empty string.

  
::rcs::decodeRcsPatch text

  
Converts the text argument into a patch command list (PCL) as
      specified in the section RCS PATCH COMMAND LIST and returns this
      list as its result. It is assumed that the input text is in diff -n
      format, also known as RCS patch format, as specified in the
      section RCS PATCH FORMAT. Please note that the command ignores
      no-ops in the input, in other words the resulting PCL contains only
      instructions doing something.

  
::rcs::encodeRcsPatch pcmds

  
This command provides the complementary operation to
      ::rcs::decodeRcsPatch. It convert a patch comand list (PCL) list as
      specified in the section RCS PATCH COMMAND LIST back into a text in
      RCS PATCH FORMAT and returns that text as its result.
    
Note that this command and ::rcs::decodeRcsPatch are
        not exactly complementary, as the latter strips no-ops from its input,
        which the encoder cannot put back anymore into the generated RCS patch.
        In other words, the result of a decode/encode step may not match the
        original input at the character level, but it will match it at the
        functional level.

  

  
::rcs::applyRcsPatch text pcmds

  
This operation applies a patch in the form of a PCL to a text given in the
      form of a dictionary and returns the modified text, again as dictionary,
      as its result.
    
To handle actual text use the commands ::rcs::text2dict
        (or equivalent) and ::rcs::decodeRcsPatch to transform the inputs
        into data structures acceptable to this command. Analogously use the
        command ::rcs::dict2text (or equivalent) to transform the result
        of this command into actuall text as required.

  










A text dictionary is a dictionary whose keys are integer numbers
    and text strings as the associated values. The keys represent the line
    numbers of a text and the values the text of that line. Note that one text
    can have many representations as a dictionary, as the index values only have
    to be properly ordered for reconstruction, their exact values do not matter.
    Similarly the strings may actually span multiple physical lines.


The text




Hello World,
how are you ?
Fine, and you ?


for example can be represented by




{{1 {Hello World,}} {2 {how are you ?}} {3 {Fine, and you ?}}}


or




{{5 {Hello World,}} {8 {how are you ?}} {9 {Fine, and you ?}}}


or




{{-1 {Hello World,
how are you ?}} {4 {Fine, and you ?}}}


The first dictionary is the canonical representation of the
    text, with line numbers starting at 1, increasing in steps of
    1 and without gaps, and each value representing exactly one physical
    line.


All the commands creating dictionaries from text will return the
    canonical representation of their input text. The commands taking a
    dictionary and returning text will generally accept all representations,
    canonical or not.


The result of applying a patch to a text dictionary will in
    general cause the dictionary to become non-canonical.








A patch is in general a series of instructions how to
    transform an input text T into a different text T', and also encoded in text
    form as well.


The text format for patches understood by this package is a very
    simple one, known under the names RCS patch or diff -n
  format.


Patches in this format contain only two different commands, for
    the deletion of old text, and addition of new text. The replacement of some
    text by a different text is handled as combination of a deletion following
    by an addition.


The format is line oriented, with each line containing either a
    command or text data associated with the preceding command. The first line
    of a RCS patch is always a command line.


The commands are:



  
""

  
The empty line is a command which does nothing.

  
"astart n"

  
A line starting with the character a is a command for the addition
      of text to the output. It is followed by n lines of text data. When
      applying the patch the data is added just between the lines start
      and start+1. The same effect is had by appending the data to the
      existing text on line start. A non-existing line start is
      created.

  
"dstart n"

  
A line starting with the character d is a command for the deletion
      of text from the output. When applied it deletes n lines of text,
      and the first line deleted is at index start.




Note that the line indices start always refer to the text
    which is transformed as it is in its original state, without taking the
    precending changes into account.


Note also that the instruction have to be applied in the order
    they occur in the patch, or in a manner which produces the same result as
    in-order application.


This is the format of results returned by the command
    ::rcs::decodeRcsPatch and accepted by the commands
    ::rcs::encodeRcsPatch and ::rcs::appplyRcsPatch resp. Note
    however that the decoder will strip no-op commands, and the encoder will not
    generate no-ops, making them not fully complementary at the textual level,
    only at the functional level.


And example of a RCS patch is




d1 2
d4 1
a4 2
The named is the mother of all things.
a11 3
They both may be called deep and profound.
Deeper and more profound,
The door of all subtleties!








Patch command lists (sort: PCL's) are the data structures
    generated by patch decoder command and accepted by the patch encoder and
    applicator commands. They represent RCS patches in the form of Tcl data
    structures.


A PCL is a list where each element represents a single patch
    instruction, either an addition, or a deletion. The elements are lists
    themselves, where the first item specifies the command and the remainder
    represent the arguments of the command.



  

  
This is the instruction for the addition of text. It has two arguments,
      the index of the line where to add the text, and the text to add, in this
      order.

  

  
This is the instruction for the deletion of text. It has two arguments,
      the index of the line where to start deleting text, and the number of
      lines to delete, in this order.




This is the format returned by the patch decoder command and
    accepted as input by the patch encoder and applicator commands.


An example for a patch command is shown below, it represents the
    example RCS patch found in section RCS PATCH FORMAT.




{{d 1 2} {d 4 1} {a 4 {The named is the mother of all things.
}} {a 11 {They both may be called deep and profound.
Deeper and more profound,
The door of all subtleties!}}}








This document, and the package it describes, will undoubtedly
    contain bugs and other problems. Please report such in the category
    rcs 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.








struct, textutil








CVS, RCS, RCS patch, SCCS, diff -n format, patching, text
    conversion, text differences








Text processing








Copyright (c) 2005, Andreas Kupries <andreas_kupries@users.sourceforge.net>
Copyright (c) 2005, Colin McCormack <coldstore@users.sourceforge.net>








  

    2.0.2
    rcs