1rcs(n) RCS low level utilities rcs(n)
2______________________________________________________________________________
6
8 rcs - RCS low level utilities
9
11 package require Tcl 8.4
12 package require rcs ?0.1?
14 ::rcs::text2dict text
16 ::rcs::dict2text dict
18 ::rcs::file2dict filename
20 ::rcs::dict2file filename dict
22 ::rcs::decodeRcsPatch text
24 ::rcs::encodeRcsPatch pcmds
26 ::rcs::applyRcsPatch text pcmds
28_________________________________________________________________
30
32 The Revision Control System, short RCS, is a set of applications and
33 related data formats which allow a system to persist the history of
34 changes to a text. It, and its relative SCCS are the basis for many
35 other such systems, like CVS, etc.
36 This package does not implement RCS.
38 It only provides a number of low level commands which should be useful
40 in the implementation of any revision management system, namely:
41 [1] The conversion of texts into and out of a data structures which
43 allow the easy modification of such text by patches, i.e.
44 sequences of instructions for the transformation of one text
45 into an other.
46 [2] And the conversion of one particular format for patches, the so-
48 called RCS patches, into and out of data structures which allow
49 their easy application to texts.
50
52 ::rcs::text2dict text
53 Converts the argument text into a dictionary containing and rep‐
54 resenting the same text in an indexed form and returns that dic‐
55 tionary as its result. More information about the format of the
56 result can be found in section TEXT DICT DATA STRUCTURE. This
57 command returns the canonical representation of the input.
58 ::rcs::dict2text dict
60 This command provides the complementary operation to
61 ::rcs::text2dict. It converts a dictionary in the form described
62 in section TEXT DICT DATA STRUCTURE back into a text and returns
63 that text as its result. The command does accept non-canonical
64 representations of the text as its input.
65 ::rcs::file2dict filename
67 This command is identical to ::rcs::text2dict, except that it
68 reads the text to convert from the file with path filename. The
69 file has to exist and must be readable as well.
70 ::rcs::dict2file filename dict
72 This command is identical to ::rcs::2dict2text, except that it
73 stores the resulting text in the file with path filename. The
74 file is created if it did not exist, and must be writable. The
75 result of the command is the empty string.
76 ::rcs::decodeRcsPatch text
78 Converts the text argument into a patch command list (PCL) as
79 specified in the section RCS PATCH COMMAND LIST and returns this
80 list as its result. It is assumed that the input text is in
81 diff -n format, also known as RCS patch format, as specified in
82 the section RCS PATCH FORMAT. Please note that the command
83 ignores no-ops in the input, in other words the resulting PCL
84 contains only instructions doing something.
85 ::rcs::encodeRcsPatch pcmds
87 This command provides the complementary operation to
88 ::rcs::decodeRcsPatch. It convert a patch comand list (PCL) list
89 as specified in the section RCS PATCH COMMAND LIST back into a
90 text in RCS PATCH FORMAT and returns that text as its result.
91 Note that this command and ::rcs::decodeRcsPatch are not exactly
93 complementary, as the latter strips no-ops from its input, which
94 the encoder cannot put back anymore into the generated RCS
95 patch. In other words, the result of a decode/encode step may
96 not match the original input at the character level, but it will
97 match it at the functional level.
98 ::rcs::applyRcsPatch text pcmds
100 This operation applies a patch in the form of a PCL to a text
101 given in the form of a dictionary and returns the modified text,
102 again as dictionary, as its result.
103 To handle actual text use the commands ::rcs::text2dict (or
105 equivalent) and ::rcs::decodeRcsPatch to transform the inputs
106 into data structures acceptable to this command. Analogously use
107 the command ::rcs::dict2text (or equivalent) to transform the
108 result of this command into actuall text as required.
109
111 A text dictionary is a dictionary whose keys are integer numbers and
112 text strings as the associated values. The keys represent the line num‐
113 bers of a text and the values the text of that line. Note that one
114 text can have many representations as a dictionary, as the index values
115 only have to be properly ordered for reconstruction, their exact values
116 do not matter. Similarly the strings may actually span multiple physi‐
117 cal lines.
118 The text
120 Hello World,
122 how are you ?
123 Fine, and you ?
124 for example can be represented by
126 {{1 {Hello World,}} {2 {how are you ?}} {3 {Fine, and you ?}}}
128 or
130 {{5 {Hello World,}} {8 {how are you ?}} {9 {Fine, and you ?}}}
132 or
134 {{-1 {Hello World,
136 how are you ?}} {4 {Fine, and you ?}}}
137 The first dictionary is the canonical representation of the text, with
139 line numbers starting at 1, increasing in steps of 1 and without gaps,
140 and each value representing exactly one physical line.
141 All the commands creating dictionaries from text will return the canon‐
143 ical representation of their input text. The commands taking a dictio‐
144 nary and returning text will generally accept all representations,
145 canonical or not.
146 The result of applying a patch to a text dictionary will in general
148 cause the dictionary to become non-canonical.
149
151 A patch is in general a series of instructions how to transform an
152 input text T into a different text T', and also encoded in text form as
153 well.
154 The text format for patches understood by this package is a very simple
156 one, known under the names RCS patch or diff -n format.
157 Patches in this format contain only two different commands, for the
159 deletion of old text, and addition of new text. The replacement of some
160 text by a different text is handled as combination of a deletion fol‐
161 lowing by an addition.
162 The format is line oriented, with each line containing either a command
164 or text data associated with the preceding command. The first line of
165 a RCS patch is always a command line.
166 The commands are:
168 "" The empty line is a command which does nothing.
170 "astart n"
172 A line starting with the character a is a command for the addi‐
173 tion of text to the output. It is followed by n lines of text
174 data. When applying the patch the data is added just between the
175 lines start and start+1. The same effect is had by appending the
176 data to the existing text on line start. A non-existing line
177 start is created.
178 "dstart n"
180 A line starting with the character d is a command for the dele‐
181 tion of text from the output. When applied it deletes n lines of
182 text, and the first line deleted is at index start.
183 Note that the line indices start always refer to the text which is
185 transformed as it is in its original state, without taking the precend‐
186 ing changes into account.
187 Note also that the instruction have to be applied in the order they
189 occur in the patch, or in a manner which produces the same result as
190 in-order application.
191 This is the format of results returned by the command ::rcs::decodeRc‐
193 sPatch and accepted by the commands ::rcs::encodeRcsPatch and
194 ::rcs::appplyRcsPatch resp. Note however that the decoder will strip
195 no-op commands, and the encoder will not generate no-ops, making them
196 not fully complementary at the textual level, only at the functional
197 level.
198 And example of a RCS patch is
200 d1 2
202 d4 1
203 a4 2
204 The named is the mother of all things.
205 a11 3
207 They both may be called deep and profound.
208 Deeper and more profound,
209 The door of all subtleties!
210
212 Patch command lists (sort: PCL's) are the data structures generated by
213 patch decoder command and accepted by the patch encoder and applicator
214 commands. They represent RCS patches in the form of Tcl data struc‐
215 tures.
216 A PCL is a list where each element represents a single patch instruc‐
218 tion, either an addition, or a deletion. The elements are lists them‐
219 selves, where the first item specifies the command and the remainder
220 represent the arguments of the command.
221 a This is the instruction for the addition of text. It has two
223 arguments, the index of the line where to add the text, and the
224 text to add, in this order.
225 d This is the instruction for the deletion of text. It has two
227 arguments, the index of the line where to start deleting text,
228 and the number of lines to delete, in this order.
229 This is the format returned by the patch decoder command and accepted
231 as input by the patch encoder and applicator commands.
232 An example for a patch command is shown below, it represents the exam‐
234 ple RCS patch found in section RCS PATCH FORMAT.
235 {{d 1 2} {d 4 1} {a 4 {The named is the mother of all things.
237 }} {a 11 {They both may be called deep and profound.
239 Deeper and more profound,
240 The door of all subtleties!}}}
241
243 This document, and the package it describes, will undoubtedly contain
244 bugs and other problems. Please report such in the category rcs of the
245 Tcllib SF Trackers [http://sourceforge.net/tracker/?group_id=12883].
246 Please also report any ideas for enhancements you may have for either
247 package and/or documentation.
248
250 struct, textutil
251
253 CVS, RCS, RCS patch, SCCS, diff -n format, patching, text conversion,
254 text differences
255
257 Copyright (c) 2005, Andreas Kupries <andreas_kupries@users.sourceforge.net>
258 Copyright (c) 2005, Colin McCormack <coldstore@users.sourceforge.net>
259rcs 2.0.2 rcs(n)