NETMOD Working Group K. Watsen Internet-Draft Watsen Networks Intended status: Best Current Practice A. Farrel Expires: October 8, 2019 Old Dog Consulting Q. Wu Huawei Technologies April 6, 2019 Handling Long Lines in Inclusions in Internet-Drafts and RFCs draft-ietf-netmod-artwork-folding-02 Abstract This document defines a simple and yet time-proven strategy for handling long lines in inclusions in internet drafts and RFCs using a backslash ('\') character to indicate where line-folding has occurred. The strategy works on any text-based content, but is primarily intended for a structured sequence of lines rather than for two-dimensional imagery. The approach produces consistent results, regardless of the content, that is both self-documenting and enables automated reconstitution of the original content. 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 October 8, 2019. Copyright Notice Copyright (c) 2019 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 Watsen, et al. Expires October 8, 2019 [Page 1] Internet-Draft Handling Long Lines in Inclusions April 2019 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 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Applicability Statement . . . . . . . . . . . . . . . . . . . 3 3. Requirements Language . . . . . . . . . . . . . . . . . . . . 4 4. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.1. Automated Folding of Long Lines in Text Content . . . . . 4 4.2. Automated Reconstitution of the Original Text Content . . 4 5. Limitations . . . . . . . . . . . . . . . . . . . . . . . . . 5 5.1. Not Recommended for Graphical Artwork . . . . . . . . . . 5 5.2. Doesn't Work as Well as Format-Specific Options . . . . . 5 6. Two Folding Strategies . . . . . . . . . . . . . . . . . . . 5 6.1. Comparison . . . . . . . . . . . . . . . . . . . . . . . 6 6.2. Recommendation . . . . . . . . . . . . . . . . . . . . . 6 7. The Single Backslash Strategy ('\') . . . . . . . . . . . . . 6 7.1. Folded Structure . . . . . . . . . . . . . . . . . . . . 6 7.1.1. Header . . . . . . . . . . . . . . . . . . . . . . . 6 7.1.2. Body . . . . . . . . . . . . . . . . . . . . . . . . 7 7.2. Algorithm . . . . . . . . . . . . . . . . . . . . . . . . 7 7.2.1. Folding . . . . . . . . . . . . . . . . . . . . . . . 7 7.2.2. Unfolding . . . . . . . . . . . . . . . . . . . . . . 8 8. The Double Backslash Strategy ('\\') . . . . . . . . . . . . 9 8.1. Folded Structure . . . . . . . . . . . . . . . . . . . . 9 8.1.1. Header . . . . . . . . . . . . . . . . . . . . . . . 9 8.1.2. Body . . . . . . . . . . . . . . . . . . . . . . . . 9 8.2. Algorithm . . . . . . . . . . . . . . . . . . . . . . . . 10 8.2.1. Folding . . . . . . . . . . . . . . . . . . . . . . . 10 8.2.2. Unfolding . . . . . . . . . . . . . . . . . . . . . . 11 9. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 12 9.1. Example Showing Boundary Conditions . . . . . . . . . . . 12 9.1.1. Using '\' . . . . . . . . . . . . . . . . . . . . . . 12 9.1.2. Using '\\' . . . . . . . . . . . . . . . . . . . . . 12 9.2. Example Showing Multiple Wraps of a Single Line . . . . . 13 9.2.1. Using '\' . . . . . . . . . . . . . . . . . . . . . . 13 9.2.2. Using '\\' . . . . . . . . . . . . . . . . . . . . . 13 9.3. Example Showing Smart Folding . . . . . . . . . . . . . . 13 9.3.1. Using '\' . . . . . . . . . . . . . . . . . . . . . . 13 9.3.2. Using '\\' . . . . . . . . . . . . . . . . . . . . . 14 10. Security Considerations . . . . . . . . . . . . . . . . . . . 15 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 Watsen, et al. Expires October 8, 2019 [Page 2] Internet-Draft Handling Long Lines in Inclusions April 2019 12.1. Normative References . . . . . . . . . . . . . . . . . . 16 12.2. Informative References . . . . . . . . . . . . . . . . . 16 Appendix A. POSIX Shell Script . . . . . . . . . . . . . . . . . 17 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 23 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23 1. Introduction [RFC7994] sets out the requirements for plain-text RFCs and states that each line of an RFC (and hence of an Internet-Draft) must be limited to 72 characters followed by the character sequence that denotes an end-of-line (EOL). Internet-Drafts and RFCs often include example text or code fragments. Many times the example text or code exceeds the 72 character line-length limit. The `xml2rfc` utility does not attempt to wrap the content of such inclusions, simply issuing a warning whenever lines exceed 69 characters. According to the RFC Editor, there is currently no convention in place for how to handle long lines in such inclusions, other than advising authors to clearly indicate what manipulation has occurred. This document introduces a simple and yet time-proven strategy for handling long lines using a backslash ('\') character to indicate where line-folding has occurred. The strategy works on any text based inclusion, but is primarily intended for a structured sequence of lines, such as would be referenced by the element defined in Section 2.48 of [RFC7991], rather than for two-dimensional imagery, such as would be referenced by the element defined in Section 2.5 of [RFC7991]. The approach produces consistent results, regardless of the content, that is both self-documenting and enables automated reconstitution of the original content. Note that text files are represented as lines having their first character in column 1, and a line length of N where the last character is in the Nth column and is immediately followed by an end of line character sequence. 2. Applicability Statement The format and algorithm defined in this document may be used in any context, whether for IETF documents or in other situations where structured folding is desired. Within the IETF, this work primarily targets the xml2rfc v3 element (Section 2.48 of [RFC7991]) and the xml2rfc v2 element (Section 2.5 of [RFC7749]) that, for lack of a better option, is currently used for both source code and artwork. Watsen, et al. Expires October 8, 2019 [Page 3] Internet-Draft Handling Long Lines in Inclusions April 2019 This work may be also be used for the xml2rfc v3 element (Section 2.5 of [RFC7991]) but, as described in Section 5.1, it is generally not recommended. 3. 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 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 4. Goals 4.1. Automated Folding of Long Lines in Text Content Automated folding of long lines is needed in order to support draft compilations that entail a) validation of source input files (e.g., XML, JSON, ABNF, ASN.1) and/or b) dynamic generation of output, using a tool that doesn't observe line lengths, that is stitched into the final document 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 entail them having some long lines. Thus, these source files need to be modified before inclusion in the document in order to satisfy the line length limits. This modification SHOULD be automated to reduce effort and errors resulting from manual processing. Similarly, dynamically generated output (e.g., tree diagrams) must also be modified, if necessary, in order for the resulting document to satisfy the line length limits. When needed, this effort again SHOULD be automated to reduce effort and errors resulting from manual processing. 4.2. Automated Reconstitution of the Original Text Content Automated reconstitution of the original content is needed to support validation of text-based inclusions extracted from documents. YANG [RFC7950] modules are already extracted from Internet-Drafts and validated as part of the draft-submission process. Additionally, there has been some discussion regarding needing to also validate instance examples (i.e., XML/JSON documents) contained within Internet-Drafts ([yang-doctors-thread]). Thus, it SHOULD be possible to mechanically reconstitute the original text content in order to utilize such tooling. Watsen, et al. Expires October 8, 2019 [Page 4] Internet-Draft Handling Long Lines in Inclusions April 2019 5. Limitations 5.1. Not Recommended for Graphical Artwork While the solution presented in this document will work on any kind of text-based content, it is most useful on content that represents source code (XML, JSON, etc.) or, more generally, on content that has not been laid out in two dimensions (e.g., diagrams). Fundamentally, the issue is whether the text content remains readable once folded. Text content that is unpredictable is especially susceptible to looking bad when folded; falling into this category are most UML diagrams, YANG tree diagrams, and ASCII art in general. It is NOT RECOMMENDED to use the solution presented in this document on graphical artwork. 5.2. Doesn't Work as Well as Format-Specific Options The solution presented in this document works generically for all text-based content, as it only views content as plain text. However, various formats sometimes have built-in mechanisms that are better suited to prevent long lines. For instance, both the `pyang` and `yanglint` utilities have the command line option "--tree-line-length" that can be used to indicate a desired maximum line length for when generating tree diagrams [RFC8340]. In another example, some source formats (e.g., YANG [RFC7950]) allow any quoted string to be broken up into substrings separated by a concatenation character (e.g., '+'), any of which can be on a different line. In yet another example, some languages allow factoring blocks of code into call outs, such as functions. Using such call outs is especially helpful when in some deeply-nested code, as they typically reset the indentation back to the first column. It is RECOMMENDED that authors do as much as possible within the selected format to avoid long lines. 6. Two Folding Strategies This document defines two nearly identical strategies for folding text-based content. Watsen, et al. Expires October 8, 2019 [Page 5] Internet-Draft Handling Long Lines in Inclusions April 2019 The Single Backslash Strategy ('\'): Uses a backslash ('\') character at the end of the line where folding occurs, and assumes that the continuation begins at the first non- whitespace character on the following line. The Double Backslash Strategy ('\\'): Uses a backslash ('\') character at the end of the line where folding occurs, and assumes that the continuation begins after a second backslash ('\') character on the following line. 6.1. Comparison The first strategy produces more readable output, however it is significantly more likely to encounter unfoldable input (e.g., there is exists a line anywhere in the input ending with a backslash character, or there exists a long line containing only space and backslash characters) and, for long lines that can be folded, automation implementations are likely to encounter scenarios that will produce errors without special care. The second strategy produces less readable output, but is unlikely to encounter unfoldable input, there are no long lines that cannot be folded, and no special care is required for when folding a long line. 6.2. Recommendation It is RECOMMENDED for implementations to first attempt to fold content using the single backslash strategy and, only in the unlikely event that it cannot fold the input or the folding logic is unable to cope with a contingency occurring on the desired folding column, then fallback to the double backslash strategy. 7. The Single Backslash Strategy ('\') 7.1. Folded Structure Text content that has been folded as specified by this strategy MUST adhere to the following structure. 7.1.1. Header The header is two lines long. The first line is the following 45-character string that MAY be surrounded by any number of printable characters. This first line cannot itself be folded. NOTE: '\' line wrapping per BCP XX (RFC XXXX) Watsen, et al. Expires October 8, 2019 [Page 6] Internet-Draft Handling Long Lines in Inclusions April 2019 [Note to RFC Editor: Please replace XX and XXXX with the numbers assigned to this document and delete this note. Please make this change in multiple places in this document.] The second line is a blank line. This line provides visual separation for readability. 7.1.2. Body The character encoding is the same as described in Section 2 of [RFC7994], except that, per [RFC7991], tab characters are prohibited. Lines that have a backslash ('\') occurring as the last character in a line are considered "folded". Really long lines may be folded multiple times. 7.2. Algorithm This section describes the process for folding and unfolding long lines when they are encountered in a single instance of text content. It is assumed that another process inserts/extracts the individual text content instances to/from an Internet-Draft or RFC. For example, the `xiax` utility [xiax] does this. 7.2.1. Folding Folding is assumed to be automated although authors may perform the folding steps manually. Determine the desired maximum line length from input to the automated line-wrapping process, such as from a command line parameter. If no value is explicitly specified, the value "69" SHOULD be used. Ensure that the desired maximum line length is not less than the minimum header, which is 46 characters. If the desired maximum line length is less than this minimum, exit (this text-based content cannot be folded). Scan the text content for horizontal tab characters. If any horizontal tab characters appear, either resolve them to space characters or exit, forcing the input provider to convert them to space characters themselves first. Scan the text content to see if any line exceeds the desired maximum. If no line exceeds the desired maximum, exit (this text content does not need to be folded). Watsen, et al. Expires October 8, 2019 [Page 7] Internet-Draft Handling Long Lines in Inclusions April 2019 Scan the text content to ensure no existing lines already end with a backslash ('\') character, as this would lead to an ambiguous result. If such a line is found, exit (this text content cannot be folded). If this text content needs to and can be folded, insert the header described in Section 7.1.1, ensuring that any additional printable characters surrounding the header does not result in a line exceeding the desired maximum.. For each line in the text content, from top-to-bottom, if the line exceeds the desired maximum, then fold the line by: 1. Determine where the fold will occur. This location MUST be before or at the desired maximum column, and MUST NOT precede a space (' ') character. 2. At the location where the fold is to occur, insert a backslash ('\') character followed by the end of line character sequence. 3. On the following line, insert any number of space (' ') characters. The result of the previous operation is that the next line starts with an arbitrary number of space (' ') characters, followed by the character that was previously occupying the position where the fold occurred. Continue in this manner until reaching the end of the text content. Note that this algorithm naturally addresses the case where the remainder of a folded line is still longer than the desired maximum, and hence needs to be folded again, ad infinitum. The process described in this section is illustrated by the "fold_it_1()" function in Appendix A. 7.2.2. Unfolding All unfolding is assumed to be automated, although a reader will mentally perform the act of unfolding the text to understand the true nature of the original text content. Scan the beginning of the text content for the header described in Section 7.1.1. If the header is not present, starting on the first line of the text content, exit (this text contents does not need to be unfolded). Remove the 2-line header from the text content. Watsen, et al. Expires October 8, 2019 [Page 8] Internet-Draft Handling Long Lines in Inclusions April 2019 For each line in the text content, from top-to-bottom, if the line has a backslash ('\') character immediately followed by the end of line character sequence, then the line can be unfolded. Remove the backslash ('\') character, the end of line character sequence, and any leading space (' ') characters, which will bring up the next line. Then continue to scan each line in the text content starting with the current line (in case it was multiply folded). Continue in this manner until reaching the end of the text content. The process described in this section is illustrated by the "unfold_it_1()" function in Appendix A. 8. The Double Backslash Strategy ('\\') 8.1. Folded Structure Text content that has been folded as specified by this strategy MUST adhere to the following structure. 8.1.1. Header The header is two lines long. The first line is the following 46-character string that MAY be surrounded by any number of printable characters. This first line cannot itself be folded. NOTE: '\\' line wrapping per BCP XX (RFC XXXX) [Note to RFC Editor: Please replace XX and XXXX with the numbers assigned to this document and delete this note. Please make this change in multiple places in this document.] The second line is a blank line. This line provides visual separation for readability. 8.1.2. Body The character encoding is the same as described in Section 2 of [RFC7994], except that, per [RFC7991], tab characters are prohibited. Lines that have a backslash ('\') occurring as the last character in a line immediately followed by the end of line character sequence, when the subsequent line starts with a backslash ('\') as the first non-space (' ') character, are considered "folded". Really long lines may be folded multiple times. Watsen, et al. Expires October 8, 2019 [Page 9] Internet-Draft Handling Long Lines in Inclusions April 2019 8.2. Algorithm This section describes the process for folding and unfolding long lines when they are encountered in a single instance of text content. It is assumed that another process inserts/extracts the individual text content instances to/from an Internet-Draft or RFC. For example, the `xiax` utility [xiax] does this. 8.2.1. Folding Folding is assumed to be automated, although authors may perform the folding steps manually. Determine the desired maximum line length from input to the automated line-wrapping process, such as from a command line parameter. If no value is explicitly specified, the value "69" SHOULD be used. Ensure that the desired maximum line length is not less than the minimum header, which is 45 characters. If the desired maximum line length is less than this minimum, exit (this text-based content cannot be folded). Scan the text content for horizontal tab characters. If any horizontal tab characters appear, either resolve them to space characters or exit, forcing the input provider to convert them to space characters themselves first. Scan the text content to see if any line exceeds the desired maximum. If no line exceeds the desired maximum, exit (this text content does not need to be folded). Scan the text content to ensure no existing lines already end with a backslash ('\') character while the subsequent line starts with a backslash ('\') character as the first non-space (' ') character, as this would lead to an ambiguous result. If such a line is found, exit (this text content cannot be folded). If this text content needs to and can be folded, insert the header described in Section 8.1.1, ensuring that any additional printable characters surrounding the header does not result in a line exceeding the desired maximum.. For each line in the text content, from top-to-bottom, if the line exceeds the desired maximum, then fold the line by: 1. Determine where the fold will occur. This location MUST be before or at the desired maximum column. Watsen, et al. Expires October 8, 2019 [Page 10] Internet-Draft Handling Long Lines in Inclusions April 2019 2. At the location where the fold is to occur, insert a first backslash ('\') character followed by the end of line character sequence. 3. On the following line, insert any number of space (' ') characters followed by a second backslash ('\') character. The result of the previous operation is that the next line starts with an arbitrary number of space (' ') characters, followed by a backslash ('\') character, immediately followed by the character that was previously occupying the position where the fold occurred. Continue in this manner until reaching the end of the text content. Note that this algorithm naturally addresses the case where the remainder of a folded line is still longer than the desired maximum, and hence needs to be folded again, ad infinitum. The process described in this section is illustrated by the "fold_it_2()" function in Appendix A. 8.2.2. Unfolding All unfolding is assumed to be automated although a reader will mentally perform the act of unfolding the text to understand the true nature of the original text content. Scan the beginning of the text content for the header described in Section 8.1.1. If the header is not present, starting on the first line of the text content, exit (this text content does not need to be unfolded). Remove the 2-line header from the text content. For each line in the text content, from top-to-bottom, if the line has a backslash ('\') character immediately followed by the end of line character sequence, and if the next line has a backslash ('\') character as the first non-space (' ') character, then the lines can be unfolded. Remove the first backslash ('\') character, the end of line character sequence, any leading space (' ') characters, and the second backslash ('\') character, which will bring up the next line. Then continue to scan each line in the text content starting with the current line (in case it was multiply folded). Continue in this manner until reaching the end of the text content. The process described in this section is illustrated by the "unfold_it_2()" function in Appendix A. Watsen, et al. Expires October 8, 2019 [Page 11] Internet-Draft Handling Long Lines in Inclusions April 2019 9. Examples The following self-documenting examples illustrate folded text-based content. The source text content cannot be presented here, as it would again be folded. Alas, only the results can be provided. 9.1. Example Showing Boundary Conditions This example illustrates boundary condition. The input contains seven lines, each line one character longer than the previous line. Numbers for counting purposes. The default desired maximum column value "69" is used. 9.1.1. Using '\' =========== NOTE: '\' line wrapping per BCP XX (RFC XXXX) =========== 123456789012345678901234567890123456789012345678901234567890123456 1234567890123456789012345678901234567890123456789012345678901234567 12345678901234567890123456789012345678901234567890123456789012345678 123456789012345678901234567890123456789012345678901234567890123456789 12345678901234567890123456789012345678901234567890123456789012345678\ 90 12345678901234567890123456789012345678901234567890123456789012345678\ 901 12345678901234567890123456789012345678901234567890123456789012345678\ 9012 9.1.2. Using '\\' ========== NOTE: '\\' line wrapping per BCP XX (RFC XXXX) =========== 123456789012345678901234567890123456789012345678901234567890123456 1234567890123456789012345678901234567890123456789012345678901234567 12345678901234567890123456789012345678901234567890123456789012345678 123456789012345678901234567890123456789012345678901234567890123456789 12345678901234567890123456789012345678901234567890123456789012345678\ \90 12345678901234567890123456789012345678901234567890123456789012345678\ \901 12345678901234567890123456789012345678901234567890123456789012345678\ \9012 Watsen, et al. Expires October 8, 2019 [Page 12] Internet-Draft Handling Long Lines in Inclusions April 2019 9.2. Example Showing Multiple Wraps of a Single Line This example illustrates what happens when very long line needs to be folded multiple times. The input contains one line containing 280 characters. Numbers for counting purposes. The default desired maximum column value "69" is used. 9.2.1. Using '\' =========== NOTE: '\' line wrapping per BCP XX (RFC XXXX) =========== 12345678901234567890123456789012345678901234567890123456789012345678\ 90123456789012345678901234567890123456789012345678901234567890123456\ 78901234567890123456789012345678901234567890123456789012345678901234\ 56789012345678901234567890123456789012345678901234567890123456789012\ 34567890 9.2.2. Using '\\' ========== NOTE: '\\' line wrapping per BCP XX (RFC XXXX) =========== 12345678901234567890123456789012345678901234567890123456789012345678\ \9012345678901234567890123456789012345678901234567890123456789012345\ \6789012345678901234567890123456789012345678901234567890123456789012\ \3456789012345678901234567890123456789012345678901234567890123456789\ \01234567890 9.3. Example Showing Smart Folding This example illustrates how readability can be improved via "smart" folding, whereby folding occurs at format-specific locations and format-specific indentations are used. The text content was manually folded, since the script in the appendix does not implement smart folding. Note that the header is surrounded by different printable characters then shown in the script-generated examples. 9.3.1. Using '\' Watsen, et al. Expires October 8, 2019 [Page 13] Internet-Draft Handling Long Lines in Inclusions April 2019 [NOTE: '\' line wrapping per BCP XX (RFC XXXX)] config-modules ietf-interfaces 2018-02-20 \ urn:ietf:params:xml:ns:yang:ietf-interfaces\ ... ... Below is the equivalent to the above, but it was folded using the script in the appendix. =========== NOTE: '\' line wrapping per BCP XX (RFC XXXX) =========== config-modules ietf-interfaces 2018-02-20 urn:ietf:params:xml:ns:yang:ietf-interfaces ... ... 9.3.2. Using '\\' Watsen, et al. Expires October 8, 2019 [Page 14] Internet-Draft Handling Long Lines in Inclusions April 2019 [NOTE: '\\' line wrapping per BCP XX (RFC XXXX)] config-modules ietf-interfaces 2018-02-20 \ \urn:ietf:params:xml:ns:yang:ietf-interfaces\ \ ... ... Below is the equivalent to the above, but it was folded using the script in the appendix. ========== NOTE: '\\' line wrapping per BCP XX (RFC XXXX) =========== config-modules ietf-interfaces 2018-02-20 urn:ietf:params:xml:ns:yang:ietf-interfaces ... ... 10. Security Considerations This BCP has no Security Considerations. Watsen, et al. Expires October 8, 2019 [Page 15] Internet-Draft Handling Long Lines in Inclusions April 2019 11. IANA Considerations This BCP has no IANA Considerations. 12. References 12.1. 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, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . 12.2. Informative References [RFC7749] Reschke, J., "The "xml2rfc" Version 2 Vocabulary", RFC 7749, DOI 10.17487/RFC7749, February 2016, . [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016, . [RFC7991] Hoffman, P., "The "xml2rfc" Version 3 Vocabulary", RFC 7991, DOI 10.17487/RFC7991, December 2016, . [RFC7994] Flanagan, H., "Requirements for Plain-Text RFCs", RFC 7994, DOI 10.17487/RFC7994, December 2016, . [RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams", BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018, . [xiax] "The `xiax` Python Package", . [yang-doctors-thread] "[yang-doctors] automating yang doctor reviews", . Watsen, et al. Expires October 8, 2019 [Page 16] Internet-Draft Handling Long Lines in Inclusions April 2019 Appendix A. POSIX Shell Script This non-normative appendix section includes a shell script that can both fold and unfold text content. Note that this script is applied only to single text content instances. #!/bin/bash --posix # must be `bash` (not `sh`) print_usage() { echo echo "Folds the text file, only if needed, at the specified" echo "column, according to BCP XX." echo echo "Usage: $0 [-s ] [-c ] [-r] -i " echo " -o " echo echo " -s: strategy to use, '1' or '2' (default: try 1, else 2)" echo " -c: column to fold on (default: 69)" echo " -r: reverses the operation" echo " -i: the input filename" echo " -o: the output filename" echo " -d: show debug messages" echo " -h: show this message" echo echo "Exit status code: zero on success, non-zero otherwise." echo } # global vars, do not edit strategy=0 # auto debug=0 reversed=0 infile="" outfile="" maxcol=69 # default, may be overridden by param hdr_txt_1="NOTE: '\\' line wrapping per BCP XX (RFC XXXX)" hdr_txt_2="NOTE: '\\\\' line wrapping per BCP XX (RFC XXXX)" equal_chars="==============================================" space_chars=" " fold_it_1() { # ensure input file doesn't contain the fold-sequence already pcregrep -M "\\\\\n" $infile >> /dev/null 2>&1 if [ $? -eq 0 ]; then echo echo "Error1: infile $infile has a line ending with a '\\'" echo "character. This file cannot be folded." echo Watsen, et al. Expires October 8, 2019 [Page 17] Internet-Draft Handling Long Lines in Inclusions April 2019 return 1 fi # stash some vars testcol=`expr "$maxcol" + 1` foldcol=`expr "$maxcol" - 1` # for the inserted '\' char # ensure input file doesn't contain whitespace on the fold column grep "^.\{$foldcol\} " $infile >> /dev/null 2>&1 if [ $? -eq 0 ]; then echo echo "Error: infile has a space character occuring after the" echo "folding column. This file cannot be folded." echo return 1 fi # center header text length=`expr ${#hdr_txt_1} + 2` left_sp=`expr \( "$maxcol" - "$length" \) / 2` right_sp=`expr "$maxcol" - "$length" - "$left_sp"` header=`printf "%.*s %s %.*s" "$left_sp" "$equal_chars"\ "$hdr_txt_1" "$right_sp" "$equal_chars"` # generate outfile echo "$header" > $outfile echo "" >> $outfile gsed "/.\{$testcol\}/s/\(.\{$foldcol\}\)/\1\\\\\n/g"\ < $infile >> $outfile return 0 } fold_it_2() { # ensure input file doesn't contain the fold-sequence already pcregrep -M "\\\\\n[\ ]*\\\\" $infile >> /dev/null 2>&1 if [ $? -eq 0 ]; then echo echo "Error2: infile has a line ending with a '\\' character" echo "followed by a '\\' character as the first non-space" echo "character on the next line. This file cannot be folded." echo return 1 fi # center header text length=`expr ${#hdr_txt_2} + 2` left_sp=`expr \( "$maxcol" - "$length" \) / 2` Watsen, et al. Expires October 8, 2019 [Page 18] Internet-Draft Handling Long Lines in Inclusions April 2019 right_sp=`expr "$maxcol" - "$length" - "$left_sp"` header=`printf "%.*s %s %.*s" "$left_sp" "$equal_chars"\ "$hdr_txt_2" "$right_sp" "$equal_chars"` # fold using recursive passes ('g' used in fold_it_1 didn't work) if [ -z "$1" ]; then # init recursive env cp $infile /tmp/wip fi testcol=`expr "$maxcol" + 1` foldcol=`expr "$maxcol" - 1` # for the inserted '\' char gsed "/.\{$testcol\}/s/\(.\{$foldcol\}\)/\1\\\\\n\\\\/" < /tmp/wip\ >> /tmp/wip2 diff /tmp/wip /tmp/wip2 > /dev/null 2>&1 if [ $? -eq 1 ]; then mv /tmp/wip2 /tmp/wip fold_it_2 "recursing" else echo "$header" > $outfile echo "" >> $outfile cat /tmp/wip2 >> $outfile rm /tmp/wip* fi return 0 } fold_it() { # ensure input file doesn't contain a TAB grep $'\t' $infile >> /dev/null 2>&1 if [ $? -eq 0 ]; then echo echo "Error: infile contains a TAB character, which is not" echo "allowed." echo return 1 fi # check if file needs folding testcol=`expr "$maxcol" + 1` grep ".\{$testcol\}" $infile >> /dev/null 2>&1 if [ $? -ne 0 ]; then if [[ $debug -eq 1 ]]; then echo "nothing to do" fi cp $infile $outfile return -1 fi Watsen, et al. Expires October 8, 2019 [Page 19] Internet-Draft Handling Long Lines in Inclusions April 2019 if [[ $strategy -eq 1 ]]; then fold_it_1 return $? fi if [[ $strategy -eq 2 ]]; then fold_it_2 return $? fi fold_it_1 if [ $? -ne 0 ]; then fold_it_2 return $? fi return 0 } unfold_it_1() { # output all but the first two lines (the header) to wip file awk "NR>2" $infile > /tmp/wip # unfold wip file gsed ":x; /.*\\\\$/N; s/\\\\\n[ ]*//; tx" /tmp/wip > $outfile # clean up and return rm /tmp/wip return 0 } unfold_it_2() { # output all but the first two lines (the header) to wip file awk "NR>2" $infile > /tmp/wip # unfold wip file gsed ":x; /.*\\\\$/N; s/\\\\\n[ ]*\\\\//; tx" /tmp/wip > $outfile # clean up and return rm /tmp/wip return 0 } unfold_it() { # check if file needs unfolding line=`head -n 1 $infile` result=`echo $line | fgrep "$hdr_txt_1"` if [ $? -eq 0 ]; then unfold_it_1 return $? fi Watsen, et al. Expires October 8, 2019 [Page 20] Internet-Draft Handling Long Lines in Inclusions April 2019 result=`echo $line | fgrep "$hdr_txt_2"` if [ $? -eq 0 ]; then unfold_it_2 return $? fi if [[ $debug -eq 1 ]]; then echo "nothing to do" fi cp $infile $outfile return -1 } process_input() { while [ "$1" != "" ]; do if [ "$1" == "-h" -o "$1" == "--help" ]; then print_usage exit 1 fi if [ "$1" == "-d" ]; then debug=1 fi if [ "$1" == "-s" ]; then strategy="$2" shift fi if [ "$1" == "-c" ]; then maxcol="$2" shift fi if [ "$1" == "-r" ]; then 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 echo "Error: infile parameter missing (use -h for help)" echo exit 1 Watsen, et al. Expires October 8, 2019 [Page 21] Internet-Draft Handling Long Lines in Inclusions April 2019 fi if [ -z "$outfile" ]; then echo echo "Error: outfile parameter missing (use -h for help)" echo exit 1 fi if [ ! -f "$infile" ]; then echo echo "Error: specified file \"$infile\" is does not exist." echo exit 1 fi if [[ $strategy -eq 2 ]]; then min_supported=`expr ${#hdr_txt_2} + 8` else min_supported=`expr ${#hdr_txt_1} + 8` fi if [ $maxcol -lt $min_supported ]; then echo echo "Error: the folding column cannot be less than" echo "$min_supported." echo exit 1 fi # this is only because the code otherwise runs out of equal_chars max_supported=`expr ${#equal_chars} + 1 + ${#hdr_txt_1} + 1\ + ${#equal_chars}` if [ $maxcol -gt $max_supported ]; then echo echo "Error: the folding column cannot be more than" echo "$max_supported." echo exit 1 fi } main() { if [ "$#" == "0" ]; then print_usage exit 1 fi process_input $@ Watsen, et al. Expires October 8, 2019 [Page 22] Internet-Draft Handling Long Lines in Inclusions April 2019 if [[ $reversed -eq 0 ]]; then fold_it code=$? else unfold_it code=$? fi exit $code } main "$@" Acknowledgements The authors thank the following folks for their various contributions (sorted by first name): Benoit Claise, Gianmarco Bruno, Italo Busi, Joel Jaeggli, Jonathan Hansford, Lou Berger, Martin Bjorklund, and Rob Wilton. The authors additionally thank the RFC Editor for confirming that there is no set convention today for handling long lines in artwork/ sourcecode inclusions. Authors' Addresses Kent Watsen Watsen Networks EMail: kent+ietf@watsen.net Adrian Farrel Old Dog Consulting EMail: adrian@olddog.co.uk Qin Wu Huawei Technologies EMail: bill.wu@huawei.com Watsen, et al. Expires October 8, 2019 [Page 23]