Internet Architecture Board (IAB) K. Watsen
Internet-Draft Juniper Networks
Intended status: Best Current Practice May 29, 2018
Expires: November 30, 2018
Handling Long Lines in Artwork in Drafts
draft-kwatsen-netmod-artwork-folding-00
Abstract
This document introduces a simple and yet time-proven strategy for
handling long lines in artwork in drafts using a backslash ('\')
character where line-folding has occurred. The strategy works on any
text based artwork, producing consistent results regardless the
artwork content. Using a per-artwork notice, the strategy is both
self-documenting and enables automated reconstitution of the original
artwork.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 30, 2018.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
Watsen Expires November 30, 2018 [Page 1]
Internet-Draft Handling Long Lines in Artwork in Drafts May 2018
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 2
3. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Automated folding of long lines in artwork . . . . . . . 3
3.2. Automated reconstitution of original artwork . . . . . . 3
4. Limitations . . . . . . . . . . . . . . . . . . . . . . . . . 3
4.1. Doesn't work well on graphical artwork . . . . . . . . . 3
4.2. Doesn't work as well as format-specific options . . . . . 4
5. Solution . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5.1. Folding . . . . . . . . . . . . . . . . . . . . . . . . . 4
5.2. Unfolding . . . . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . 5
Appendix A. POSIX Shell Script . . . . . . . . . . . . . . . . . 7
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 10
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
Internet drafts many times contain artwork that exceed the 72
character limit specified by RFC 7994 [RFC7994]. The "xml2rfc"
utility, in an effort to maintain clean formatting, issues a warning
whenever artwork lines exceed 69 characters. According to RFC
Editor, there is currently no convention in place for how to handle
long lines, other than clearly indicating that some manipulation has
occurred.
This document introduces a simple and yet time-proven strategy for
handling long lines using a backslash ('\') character where line-
folding has occurred. The strategy works on any text based artwork,
producing consistent results regardless the artwork content. Using a
per-artwork notice, the strategy is both self-documenting and enables
automated reconstitution of the original artwork.
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
Watsen Expires November 30, 2018 [Page 2]
Internet-Draft Handling Long Lines in Artwork in Drafts May 2018
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Goals
3.1. Automated folding of long lines in artwork
Automated folding of long lines is needed in order to support draft
compilations that entail a) validation of source input files (e.g.,
YANG, XML, JSON, ABNF, ASN.1) and/or b) dynamic generation of output
(e.g., tree diagrams) that are stitched into the final draft to be
submitted.
Generally, in order for tooling to be able to process input files,
the files must be in their original/natural state, which may include
having some long lines. Thus, these source files need to be modified
before inclusion in the draft in order to satisfy the line length
limits. This modification SHOULD be automated to reduce effort and
errors resulting from manual effort.
Similarly, dynamically generated output (e.g., tree diagrams) must
also be modified, if necessary, in order for the resulting I-D to
satisfy the line length limits. When needed, this effort again
SHOULD be automated to reduce effort and errors resulting from manual
effort.
3.2. Automated reconstitution of original artwork
Automated reconstitution of the original artwork is needed to support
validation of artwork extracted from drafts. Already YANG modules
are extracted from drafts and validated as part of the draft-
submission process. Additionally, there has been some discussion
regarding needing to do the same for examples contained within drafts
([yang-doctors-list]). Thus, it SHOULD be possible to mechanically
reconstitute artwork in order to satisfy the tooling input parsers.
4. Limitations
4.1. Doesn't work well on graphical artwork
While the solution presented in this document will work on any kind
of text-based artwork, it is most useful on artwork that represents
sourcecode (e.g., YANG, XML, JSON, etc.) or, more generally, on
artwork that has not been laid out in two dimensions (e.g.,
diagrams).
The issue regards the readability of the folded artwork in the draft.
Artwork that is unpredictable is especially susceptible is looking
Watsen Expires November 30, 2018 [Page 3]
Internet-Draft Handling Long Lines in Artwork in Drafts May 2018
bad when folded; falling into this category are most UML diagrams.
Artwork that is somewhat structured (e.g., YANG tree diagrams
[RFC8340]) fair better when folded, as the eyes seem to be able to
still see the vertical lines, even when they are interrupted.
It is thus NOT RECOMMENDED to use the solution presented in this
document on graphical artwork.
4.2. Doesn't work as well as format-specific options
The solution presented in this document works generically for all
artwork, as it only views artwork as plain text. However, various
formats sometimes have mechanisms that can be used to prevent long
lines.
For instance, some source formats allow any quoted string to be
broken up into substrings separated by a concatenation character
('+'), any of which can by on a different line.
In another example, some languages allow factoring out chucks of code
out into "functions" or "groupings". Using such call outs is
especially helpful when in some deeply-nested code, as it typically
resets the indentation back to the first column.
As such, it is RECOMMENDED that authors do as much as possible within
the selected format to avoid long lines.
5. Solution
The following two sections provide the folding and unfolding
algorithms that MUST be implemented to align with this BCP.
5.1. Folding
Scan the artwork to see if any line exceeds the desired maximum. If
no line exceeds the desired maximum, exit (this artwork does not need
to be folded).
Otherwise, as it is determined the artwork needs to be folded,
prepend the 3-line header (RFC Ed. please replace XX below with the
assigned value for this BCP):
\n[Note: '\' line wrapping added per BCP XX]\n\n
For each line in the artwork, from top-to-bottom, if the line exceeds
the desired maximum, then fold the line at the desired column by
inserting the string "\\n" at the column before the maximum column.
Note that the spacer is needed to give room for the '\' character.
Watsen Expires November 30, 2018 [Page 4]
Internet-Draft Handling Long Lines in Artwork in Drafts May 2018
Continue in this manner until reaching the end of the artwork. Note
that the algorithm naturally addresses the case where the remainder
of a folded line is still longer than the desired maximum.
5.2. Unfolding
Scan the artwork for the above-mentioned header. If the header is
not present in the artwork, exit (this artwork does not need to be
unfolded).
Remove the 3-line header from the artwork.
For each line in the artwork, from top-to-bottom, if the line ends in
"\\n", then remove the "\\n" and then scan the remainder of the line
to see if it again ends in "\\n", and so on.
Continue in this manner until reaching the end of the artwork.
6. Security Considerations
This BCP has no Security Considerations.
7. IANA Considerations
This BCP has no IANA Considerations.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
8.2. Informative References
[RFC7994] Flanagan, H., "Requirements for Plain-Text RFCs",
RFC 7994, DOI 10.17487/RFC7994, December 2016,
<https://www.rfc-editor.org/info/rfc7994>.
[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/info/rfc8340>.
Watsen Expires November 30, 2018 [Page 5]
Internet-Draft Handling Long Lines in Artwork in Drafts May 2018
[yang-doctors-list]
"[yang-doctors] automating yang doctor reviews",
<https://mailarchive.ietf.org/arch/msg/yang-doctors/
DCfBqgfZPAD7afzeDFlQ1Xm2X3g>.
Watsen Expires November 30, 2018 [Page 6]
Internet-Draft Handling Long Lines in Artwork in Drafts May 2018
Appendix A. POSIX Shell Script
This non-normative appendix section includes a shell script that can
both fold and unfold artwork based on the solution presented in this
document.
As a testament for the simplicity of this solution, note that at the
core of the script are the following two one-liners:
For folding: gsed "s/\(.\{$foldcol\}\)/\1\\\\\n/"
For unfolding: gsed ':x; /\\$/ { N; s/\\\n//; tx }'
=====START SCRIPT=====
#!/bin/bash
#
# the only reason why /bin/sh isn't being used
# is because "echo -n" is broken on the Mac.
print_usage() {
echo
echo "Wraps file representing IETF artwork at specified column"
echo "according to BCP XX. Note, this routine does nothing if"
echo "the infile has no lines longer than specified."
echo
echo "Usage: $0 [-r] [-c <col>] -i <infile> -o <outfile>"
echo
echo " -c: column to wrap on (default: 69)"
echo " -r: reverses the operation"
echo " -i: the input filename"
echo " -o: the output filename"
echo " -h: show this message"
echo
echo "Exit status code: zero on success, non-zero otherwise."
echo
}
# global vars, do not edit
reversed=0
infile=""
outfile=""
maxcol=69 # default, may be overridden by param
header="\n[Note: '\' line wrapping added per BCP XX]\n\n"
fold_it() {
# check if file needs folding
Watsen Expires November 30, 2018 [Page 7]
Internet-Draft Handling Long Lines in Artwork in Drafts May 2018
grep ".\{$maxcol\}" $infile >> /dev/null 2>&1
if [ $? -ne 0 ]; then
# nothing to do
cp $infile $outfile
return 1
fi
echo -ne "$header" > $outfile
foldcol=`expr "$maxcol" - 1` # spacer for the inserted '\' char
gsed "s/\(.\{$foldcol\}\)/\1\\\\\n/" < $infile >> $outfile
return 0
}
unfold_it() {
# count lines in header
numlines=`echo -ne "$header" | wc -l`
# check if file needs unfolding
echo -ne "$header" > /tmp/header
head -n $numlines $infile > /tmp/header2
diff -q /tmp/header /tmp/header2 >> /dev/null
code=$?
rm /tmp/header /tmp/header2
if [ $code -ne 0 ]; then
# nothing to do
cp $infile $outfile
return 1
fi
awk "NR>$numlines" $infile > /tmp/wip
gsed ':x; /\\$/ { N; s/\\\n//; tx }' /tmp/wip > $outfile
rm /tmp/wip
return 0
}
process_input() {
while [ "$1" != "" ]; do
if [ "$1" == "-h" -o "$1" == "--help" ]; then
print_usage
exit 1
fi
if [ "$1" == "-c" ]; then
maxcol="$2"
shift
fi
if [ "$1" == "-r" ]; then
Watsen Expires November 30, 2018 [Page 8]
Internet-Draft Handling Long Lines in Artwork in Drafts May 2018
reversed=1
fi
if [ "$1" == "-i" ]; then
infile="$2"
shift
fi
if [ "$1" == "-o" ]; then
outfile="$2"
shift
fi
shift
done
if [ -z "$infile" ]; then
echo "error: infile parameter missing."
exit 1
fi
if [ -z "$outfile" ]; then
echo "error: outfile parameter missing."
exit 1
fi
if [ ! -f "$infile" ]; then
echo "error: infile \"$infile\" does not exist."
exit 1
fi
if [ -f "$outfile" ]; then
echo "warning: outfile \"$outfile\" already exists."
fi
}
main() {
if [ "$#" == "0" ]; then
print_usage
exit 1
fi
process_input $@
if [[ $reversed -eq 0 ]]; then
fold_it
else
unfold_it
fi
exit 0
Watsen Expires November 30, 2018 [Page 9]
Internet-Draft Handling Long Lines in Artwork in Drafts May 2018
}
main "$@"
=====END SCRIPT=====
Acknowledgements
The authors thank the RFC Editor for confirming that there are no set
convention today for handling long lines in artwork.
Author's Address
Kent Watsen
Juniper Networks
EMail: kwatsen@juniper.net
Watsen Expires November 30, 2018 [Page 10]