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



____________________________________________________________________________________________________________

NAME
       rcs - RCS low level utilities

SYNOPSIS
       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

____________________________________________________________________________________________________________

DESCRIPTION
       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.


COMMANDS
       ::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 canoni-cal canonical
              cal representation of the input.

       ::rcs::dict2text dict
              This command provides the complementary operation to ::rcs::text2dict. It converts  a  dictio-nary dictionary
              nary  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  FOR-MAT. FORMAT.
              MAT.   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 dictio-nary dictionary
              nary and returns the modified text, again as dictionary, as its result.

              To handle actual text use the commands ::rcs::text2dict (or equivalent)  and  ::rcs::decodeRc-sPatch ::rcs::decodeRcsPatch
              sPatch  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.


TEXT DICT DATA STRUCTURE
       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 representa-tions, representations,
       tions, canonical or not.

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

RCS PATCH FORMAT
       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 addi-tion addition
       tion 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 origi-nal original
       nal 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 man-ner manner
       ner 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  com-mands commands
       mands ::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!

RCS PATCH COMMAND LIST
       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
       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!}}}

BUGS, IDEAS, FEEDBACK
       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://source -
       forge.net/tracker/? group_id=12883].   Please  also report any ideas for enhancements you may have for
       either package and/or documentation.

SEE ALSO
       struct, textutil

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

CATEGORY
       Text processing

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




rcs                                                 2.0.2                                             rcs(n)