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rcs(3tcl) | RCS low level utilities | rcs(3tcl) |
NAME¶
rcs - RCS low level utilitiesSYNOPSIS¶
package require Tcl 8.4DESCRIPTION¶
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 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.
- ::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.
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 textHello World, how are you ? Fine, and you ?
{{1 {Hello World,}} {2 {how are you ?}} {3 {Fine, and you ?}}}
{{5 {Hello World,}} {8 {how are you ?}} {9 {Fine, and you ?}}}
{{-1 {Hello World, how are you ?}} {4 {Fine, and you ?}}}
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 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.
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.
{{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://sourceforge.net/tracker/?group_id=12883]. Please also report any ideas for enhancements you may have for either package and/or documentation.SEE ALSO¶
struct, textutilKEYWORDS¶
CVS, RCS, RCS patch, SCCS, diff -n format, patching, text conversion, text differencesCATEGORY¶
Text processingCOPYRIGHT¶
Copyright (c) 2005, Andreas Kupries <andreas_kupries@users.sourceforge.net> Copyright (c) 2005, Colin McCormack <coldstore@users.sourceforge.net>
2.0.2 | rcs |