David A. Wheeler scripsit:
> Background: Nobody officially uses LF CR as a line ending, but sometimes
> people screw up and generate reversed LF CR line-endings. An EOL
> detector can, after reading an LF, peek to see if the next char is a CR
> (and if so consume that too), and thus be generous in what it accepts.
There's no reason to support LF CR. I'd think the most likely way for
it to get generated is that someone writes a LF as end of line, and then
someone else erroneously appends a blank line terminated by CR+LF to
that, producing LF CR LF. So treat LF CR (with or without a following
LF) as two separate lines.
> I plan to also support IBM NEL.
After pushing the NEL, CR NEL, and LS line terminators into XML 1.1,
I've concluded that it was simply a mistake. For one thing, it makes you
dependent on the details of the encoding beyond just ASCII-compatibility.
Otherwise, you can do line-breaking at the byte level, as long as you
avoid EBCDIC and UTF-16 (which XML implementations cannot do). That
works well in Lisp implementations which still have the byte=character
assumption baked in.
In practice, mainframe text files don't seem to escape the mainframe
without newline conversion as well as encoding conversion, so you don't
run across such files in the wild. As for LS, I think a single sample
file in UTF-16 issued years ago by the Unicode Consortium itself is the
only example I've ever seen: it was obsolete as soon as it was created.
("N possible line terminators? Let's define our own. Oops, now we have
N+1 line terminators.")
--
John Cowan co...@ccil.org http://ccil.org/~cowan
It's the old, old story. Droid meets droid. Droid becomes chameleon.
Droid loses chameleon, chameleon becomes blob, droid gets blob back
again. It's a classic tale. --Kryten, Red Dwarf
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