Re: DEP-5: general file syntax
On Sat, Aug 21 2010, Russ Allbery wrote:
> Ben Finney <ben+debian@benfinney.id.au> writes:
>> Lars Wirzenius <liw@liw.fi> writes:
>
>>> * Have one copyright statement per Copyright field, and have multiple
>>> instances of the field.
>
>> This is my preference, and what I've been doing in my packages.
>
> Unfortunately, this creates real challenges for parsers. I've written a
> few RFC 5322 parsers, particularly for Usenet, and allowing repetition of
> headers always causes headaches in representation. You end up having to
> add another layer of data structure, with corresponding changes to
> everything that consumes information from the parser, if you don't want to
> throw away information. It's also a divergence from the Debian control
> file format, which allows only one instance of a field per stanza,
> probably for much the same reason.
If I recall correctly, 2822 allows for header field folding:
--8<---------------cut here---------------start------------->8---
2.2. Header Fields
Header fields are lines composed of a field name, followed by a colon
(":"), followed by a field body, and terminated by CRLF. A field
name MUST be composed of printable US-ASCII characters (i.e.,
characters that have values between 33 and 126, inclusive), except
colon. A field body may be composed of any US-ASCII characters,
except for CR and LF. However, a field body may contain CRLF when
used in header "folding" and "unfolding" as described in section
2.2.3. All field bodies MUST conform to the syntax described in
sections 3 and 4 of this standard.
2.2.3. Long Header Fields
Each header field is logically a single line of characters comprising
the field name, the colon, and the field body. For convenience
however, and to deal with the 998/78 character limitations per line,
the field body portion of a header field can be split into a multiple
line representation; this is called "folding". The general rule is
that wherever this standard allows for folding white space (not
simply WSP characters), a CRLF may be inserted before any WSP. For
example, the header field:
Subject: This is a test
can be represented as:
Subject: This
is a test
Note: Though structured field bodies are defined in such a way that
folding can take place between many of the lexical tokens (and even
within some of the lexical tokens), folding SHOULD be limited to
placing the CRLF at higher-level syntactic breaks. For instance, if
a field body is defined as comma-separated values, it is recommended
that folding occur after the comma separating the structured items in
preference to other places where the field could be folded, even if
it is allowed elsewhere.
The process of moving from this folded multiple-line representation
of a header field to its single line representation is called
"unfolding". Unfolding is accomplished by simply removing any CRLF
that is immediately followed by WSP. Each header field should be
treated in its unfolded form for further syntactic and semantic
evaluation.
--8<---------------cut here---------------end--------------->8---
Can't we just "fold" long copyright header fields similarly?
manoj
--
Houston, Tranquillity Base here. The Eagle has landed. Neil Armstrong
Manoj Srivastava <srivasta@acm.org> <http://www.golden-gryphon.com/>
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