307805 - all string classes should allow dependent assignment

Status: NEW

(Core :: XPCOM, defect, P3)

Description

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Performance optimization using our string classes would be helped if all string
classes allowed dependent assignment rather than just nsDependent[C]S[ubs]tring.
 Dependent substring assignment would require a check that the class type
supports it -- and fallback to Assign (perhaps with assertion, although I'm
currently thinking without) if it doesn't.  I'd also want a version of
ns[C]AutoString that doesn't imply termination.

Preliminary patch coming.

Comment 1

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Attachment: untested patch

Untested, but compiles through xpcom.

Comment 2

[Darin Fisher]

Comment on attachment 195479 [details] [diff] [review]
untested patch

nsString implies termination (remember nsAFlatString).	I think it will be hard
to change that.

It confuses me to see nsTAutoSubstring inherit from nsTAutoString since
nsTAutoString eventually inherits from nsTSubstring.

I sort of think that it's only going to work to allow setting a dependent and
null-terminated buffer on a nsTString.

Comment 3

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

(In reply to comment #2)
> nsString implies termination (remember nsAFlatString). I think it will be hard
> to change that.

I didn't change that, with the one exception of nsTAutoSubstring.

> It confuses me to see nsTAutoSubstring inherit from nsTAutoString since
> nsTAutoString eventually inherits from nsTSubstring.
>
> I sort of think that it's only going to work to allow setting a dependent and
> null-terminated buffer on a nsTString.

Yeah, it's odd, but it's also exactly what nsStandardURL::BuildNormalizedSpec
should have been using, and I don't see any other easy way to do it.

Comment 4

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Attachment: untested patch

This is tested in that I had it in my tree for months (I'm just removing it now) and it didn't break anything, but I haven't really tested the new stuff.