[OpenAFS-devel] File Descriptor use in the vol package

[Simon Wilkinson]

On 26 Jan 2011, at 16:08, Rod Widdowson wrote:

> The vol package uses three separate types of file descriptor.
>
> FILE *f
> int fd
> FD_t


I remain a little bit confused about what the problem is here, and  
what the desired cure is. What follows is an attempt to clarify  
things ...

My assumption is that having 3 different types of file descriptor  
isn't a huge problem (it would be really nice to not have int fd, and  
FD_t, but we're always going to have 2, as long as we use both POSIX  
and native I/O).

It seems to me that the real issue is that in places we intermingle  
the second and third I/O families. On Unix, this isn't a problem  
because these two families are identical. But on Windows, where we  
have our own I/O calls in ntops.c, we'll (for example) open a file  
using "normal" open(), but then unlink it using nt_unlink(). This  
causes problems because we then don't get the unlink semantics that we  
desire.

So, there are two issues to resolve. The first is that we want to  
ensure consistency of use. That is, we don't want to be explicitly (or  
implicitly) casting between FD_t and int. In fact, it would be highly  
desirable if the compiler stopped us from doing so.

Secondly, it would be really nice to not have 3 file descriptor types.  
This would entail replacing all use of the int family with the FD_t  
family. In my view, this would be best acheived by adding a platform  
independent I/O framework to our nascent opr portability library.

Or is there more to this than I realise?

Cheers,

Simon.