[OpenAFS-devel] afs_buffer.c:DRead()

[Derek Atkins]

Why is it a void* -- can't you just define:

struct osi_file;

and then prototype the function as:

 foo (struct osi_file *tfile);

-derek

Nickolai Zeldovich <kolya@MIT.EDU> writes:

> >     tfile = afs_CFileOpen(fid[0]);
> >     sizep = (afs_int32 *)tfile;
> >     if (page * AFS_BUFFER_PAGESIZE >= *sizep) {
> >         give_up...
> > 
> > Since tfile is really a struct osi_file *, this can't possibly work except
> > by accident.
> 
> This does seem very backwards, but as far as I can tell, it actually does
> work.  As afs_osi.h says:
> 
>   struct osi_file {
>       afs_int32 size;             /* file size in bytes XXX Must be first field XXX */
>       ...
>   }
> 
> so sizep points at osi_file.size, and dereferencing it should infact give
> you the size value.  I'm really unclear on why they decided to manually
> decode struct fields, instead of using, oh, say, tfile->size.  Oh, I guess
> tfile is void*; but casting it to osi_file seems like a much better way
> to do it than this..
> 
> -- kolya
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-- 
       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
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