rcs - RCS low level utilities

       This document, and the package it describes, will undoubtedly contain bugs and  other  problems.   Please
       report  such  in  the category rcs of the TcllibTrackers [http://core.tcl.tk/tcllib/reportlist].  Please
       also report any ideas for enhancements you may have for either package and/or documentation.

       When proposing code changes, please provide unifieddiffs, i.e the output of diff-u.

       Note further that attachments are strongly preferred over inlined patches. Attachments  can  be  made  by
       going  to the Edit form of the ticket immediately after its creation, and then using the left-most button
       in the secondary navigation bar.

       Text processing

::rcs::text2dicttext
              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  TEXTDICTDATASTRUCTURE. This command returns the canonical
              representation of the input.

       ::rcs::dict2textdict
              This command provides the complementary operation to ::rcs::text2dict. It converts a dictionary in
              the form described in section TEXTDICTDATASTRUCTURE 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::file2dictfilename
              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::dict2filefilenamedict
              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::decodeRcsPatchtext
              Converts  the  text argument into a patch command list (PCL) as specified in the section RCSPATCHCOMMANDLIST and returns this list as its result.  It is assumed that the input text is in diff-nformat, also known as RCSpatch format, as specified in the section RCSPATCHFORMAT.  Please note
              that the command ignores no-ops in the input, in other  words  the  resulting  PCL  contains  only
              instructions doing something.

       ::rcs::encodeRcsPatchpcmds
              This  command  provides  the  complementary operation to ::rcs::decodeRcsPatch. It convert a patch
              comand list (PCL) list as specified in the section RCSPATCHCOMMANDLIST back into a text in  RCSPATCHFORMAT 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::applyRcsPatchtextpcmds
              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.

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

tcllib                                                 0.2                                             rcs(3tcl)

       The  RevisionControlSystem, 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 doesnot 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 RCSpatches, into  and  out
              of data structures which allow their easy application to texts.

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

       rcs - RCS low level utilities

       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.

       a      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.

       d      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 RCSPATCHFORMAT.

              {{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!}}}

       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 RCSpatch or diff-nformat.

       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 RCSpatch is always a command line.

       The commands are:

       ""     The empty line is a command which does nothing.

       "astartn"
              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.

       "dstartn"
              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!

       struct, textutil

       package require Tcl8.59

       package require rcs?0.2?::rcs::text2dicttext::rcs::dict2textdict::rcs::file2dictfilename::rcs::dict2filefilenamedict::rcs::decodeRcsPatchtext::rcs::encodeRcsPatchpcmds::rcs::applyRcsPatchtextpcmds

________________________________________________________________________________________________________________

       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.