605268 - nsIFileInputStream allows seeking past the end of the file

Status: NEW

(Core :: Networking: File, defect, P5)

Description

[Jonas Sicking (:sicking) No longer reading bugmail consistently]

Currently, if you instantiate a file-input-stream and QI to nsISeekableStream you can seek past the end of the file. This is counter to what the nsISeekableStream::Seek documentation in the interface says.

Not only can you seek past the end, but if you do, calling nsISeekableStream::Available gives very strange results. For example if you seek 10 bytes past the end, Available returns 4294967286 (2^32 - 10). But when just one byte past the end, an exception is thrown.

This behaves the same way on all platforms.

Unfortunately I can't think of a way to fix this without slowing down all SET and CUR seeks with a positive offset. I.e. making them call Available before performing the seek.


I didn't really know who to cc on this bug. If you know of anyone who has good knowledge of platform APIs, please do cc them.

Comment 1

[Firefox Bug Husbandry Bot]

Bulk change to priority: https://bugzilla.mozilla.org/show_bug.cgi?id=1399258