Re: File* argument order, argument types

On 18.02.23 01:52, Andres Freund wrote:
> I don't know what to actually propose. I guess the least bad I can see is to
> pick one type & argument order that we document to be the default, with a
> caveat placed above the functions not following the argument order.
> 
> Order wise, I think we should choose amount, offset.  For the return type we
> probably should pick ssize_t?  I don't know what we should standardize on for
> 'amount', I'd probably be inclined to go for size_t.

This reminds me that most people talk about LIMIT X OFFSET Y, even 
though what actually happens is that the offset is handled first and 
then the limit is applied.  This is also reflected in the standard SQL 
spelling OFFSET Y FETCH FIRST Z ROWS, in that order.  So, just saying 
that there is universal disagreement on the order of these things.

I think the correct order is offset, then amount.  And I think the OS C 
APIs mostly agree with that, if you look at the newer ones.  The 
exceptions are the likes of pread() and pwrite(); I think they just kept 
the signature of read() and write() and added the additional offset 
argument at the end, which I think is a sensible compromise.

For the proposed FileFallocate() I would therefore also keep the order 
of posix_fallocate(), so it would be

     FileFallocate(File file, off_t offset, off_t len, ...)