Previous: File format grammar, Up: File format [Contents][Index]
newphrase ::= id word* ";"
and used it in the admin, delta and deltatext
productions.
This allowed third-party programs to interoperate with RCS
by storing opaque (to RCS) data in the file.
As of 5.8, in the name of progress (towards more systematic file
integrity support), the only area reserved for third-party interop is in
the string value of the integrity field, specifically after the
first formfeed (U+0C).
A further restriction (for all programs) is that the integrity
value must not contain ‘@’.
Warning: This change means you cannot use rlog
(or rcs log) as a workalike for cvs log for
versions of CVS that write other kinds of metadata into the file.
If you use CVS and have access to the *,v files it writes,
you can determine if they require cvs log
by the following command:
if grep -E -q '^(deltatype|permissions|kopt)' *,v then echo 'must use "cvs log"' else echo 'probably safe to use "rcs log" (for now)' fi
The “(for now)” bit is a nod to the most probable trajectory for both RCS and CVS: away from interop.
string values.
However, whitespace cannot appear within an id, num, or
sym, and an RCS file must end with newline (U+0A).
A string value is enclosed by ‘@’ (U+40)
with internal ‘@’ characters doubled.
All other bytes (arbitrary binary data) represent themselves.
For example:
| conceptual string | persistent representation |
|---|---|
| a string of five words | @a string of five words@ |
| another, with one ’@’ char | @another, with one '@@' char@ |
| with newline and unquoted @ | @with newline and unquoted @@@ |
date keyword, are of the form
Y.m.d.H.M.S, where Y is the year, m the month
(01–12), d the day (01–31), H the hour (00–23),
M the minute (00–59), and S the second (00–60).
(These correspond to strftime format strings, with
the exception of Y, which depends on the particular year.)
Y contains just the last two digits of the year for years from
1900 through 1999, and all the digits of years thereafter.
Dates use the Gregorian calendar; times use UTC.
delta nodes form a tree.
All nodes whose numbers consist of a single pair, e.g.:
2.3 2.1 1.3
are on the trunk, and are linked through the next field in order
of decreasing numbers.
The head field in the admin node points to the head of
that sequence (i.e., contains the highest pair).
The branch node in the admin node indicates the default
branch (or revision) for most RCS operations.
If empty, the default branch is the highest branch on the trunk.
All delta nodes whose numbers consist of 2n fields (n
≥ 2), e.g.:
3.1.1.1 2.1.2.2
are linked as follows.
All nodes whose first 2n-1 number fields are identical are
linked through the next field in order of increasing numbers.
For each such sequence, the delta node whose number is identical
to the first 2n-2 number fields of the delta nodes
on that sequence is called the branchpoint.
The branches field of a node contains a list of the numbers of
the first nodes of all sequences for which it is a branchpoint.
This list is ordered in increasing numbers.
See Figure 3.1.
Head
|
v / \
--------- / \
/ \ / \ | | / \ / \
/ \ / \ | 2.1 | / \ / \
/ \ / \ | | / \ / \
/1.2.1.3\ /1.3.1.1\ | | /1.2.2.2\ /1.2.2.1.1.1\
--------- --------- --------- --------- -------------
^ ^ | ^ ^
| | v | |
/ \ | --------- / \ |
/ \ | \ 1.3 / / \ |
/ \ ---------\ / / \-----------
/1.2.1.1\ 1.3.1 \ / /1.2.2.1\ 1.2.2.1.1
--------- \ / ---------
^ | ^
| v |
| --------- |
| \ 1.2 / |
----------------------\ /---------
1.2.1 \ / 1.2.2
\ /
|
v
---------
\ 1.1 /
\ /
\ /
\ /
Figure 3.1: The organization of an example RCS file.
Previous: File format grammar, Up: File format [Contents][Index]