92478 - Rewrite nsXBLService::FetchBindingDocument so that it avoid copy

Status: RESOLVED WONTFIX

(Core :: XBL, defect)

Description

[Doug Turner (:dougt)]

nsXBLService::FetchBindingDocument could use nsIInputStream::ReadSegments to
avoid copying.  Currently it calls Read() which copies bytes into a local buffer.

Comment 1

[Doug Turner (:dougt)]

Attachment: Makes use of ReadSegments to avoid buffer copy.

Comment 2

[Doug Turner (:dougt)]

Darin, can you review this?

Comment 3

[Doug Turner (:dougt)]

reassigning to default owner.

Comment 4

[David Hyatt]

The synchronous case in this function is almost never hit, so shouldn't make
much of a difference.

If you want to check it in, sr=hyatt.

Comment 5

[Darin Fisher]

r/sr=darin

Comment 6

[Doug Turner (:dougt)]

to default.

Comment 7

[Boris Zbarsky [:bzbarsky]]

At this point we load the data using nsSyncLoadService::LoadLocalXBLDocument,
which wraps the raw stream in a buffered input stream and passes that to the
OnDataAvailable (the parser).  I assume that this in fact does do an extra copy,
right?

Comment 8

[Boris Zbarsky [:bzbarsky]]

XBL is now disabled in Firefox (Bug 1583314) and is in the process of being removed from Gecko (Bug 1566221), so closing bugs requesting changes to its implementation as wontfix.

Comment 9

[Worcester12345]

This bug is flagged with "PERF" key word. Will taking out this code negatively affect the performance at all?

Comment 10

[Boris Zbarsky [:bzbarsky]]

No. Now instead of running code that does a copy (which was bad for perf) we don't run that code at all.