If you're wondering, I'm using the following function to try to get around the fseek limitations.  It works, but it's really slow for large seeks.  If the 8KB limitation could be lifted, then this function could be serveral times faster.

http://pastebin.com/xWiQxgSB

Ugh, that is indeed ugly.  One way to fix this inconsistency would
be to avoid the stream.position to overflow (see the attached
position-no-overflow patch, which doesn't cater to writing,
though).  That would make the pastebin example to behave
reasonably.  However, that also would prohibit to read beyond the
2GB limit, so would likely break working code, and remove a
basically working feature.

Other than that, we could make the stream.position unsigned.  That
still would cause issues, because the stream layer converts
SEEK_CUR seeks to SEEK_SET[1] to cater to stream.position which is
not necessarily what ftell() would report (if the stream even
supports something like ftell()).  However, fseek() (or rather
lseek() which is used internally) expect signed offsets, so we
still couldn't seek beyond the 2GB limit – unless we'd rely on
large file support.  Not sure if that would be worth the trouble
nowadays.

[1] <https://github.com/php/php-src/blob/php-7.3.21/main/streams/streams.c#L1286-L1291>

I think we should leave that as is, but document the behavior.