Date: Sat, 13 May 2000 07:08:27 -0700 From: nathan@khmere.com To: Alfred Perlstein <bright@wintelcom.net> Cc: "hackers@FreeBSD.ORG" <hackers@FreeBSD.ORG> Subject: Re: mremap help ? or no support for FreeBSD ? so do what ? Message-ID: <391D61DA.C9793AAC@khmere.com> References: <391D39E0.934224E4@khmere.com> <20000512235721.A28383@fw.wintelcom.net>
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Alfred Perlstein wrote:
> * nathan@khmere.com <nathan@khmere.com> [000512 21:54] wrote:
> > I know that this was discussed in the past but I can't find out what to
> > do ?
> >
> > In Linux if I have to resize a mmap 'ed object I can just use mremap....
> > but in FreeBSD if, I want to resize it what do I do ?
> >
> > I have tried writing past where I know the end is and it kinda works ?
> > but why ?
> >
> > Is their a better solution besides just writing to the file and then
> > calling msync ?
> >
> > Is their new plans to make a mremap call for FreeBSD 4.x ?
>
> no.
>
> >
> > Or am I just sh%t out of luck ?
>
> Possibly, but if you describe what you are trying to accomplish
> there may be some advice available. Your misuse of msync makes me
> think that a rethinking of what you are trying to accomplish may
> be a good idea. Please explain what makes you need mremap which
> is not portable to any version of unix. I'm assuming you want your
> app to work on Solaris and other commercial systems.
>
> --
> -Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org]
> "I have the heart of a child; I keep it in a jar on my desk."
>
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Sorry !
Ok here is a snipit of what I am trying to do....
fstat(fd, &st);
if( (base = (caddr_t *) mmap(0, st.st_size, ( PROT_READ | PROT_WRITE ) ,
MAP_SHARED, fd, 0)) == MAP_FAILED)
{
MSG_ERR("cannot mmap file, exiting ! ");
_exit(1);
}
/* say st.st_size = 200, and I want to add to the end of the file more data
*/
base += 200; /* we are now at the end */
rec = (stuct rec_t *) base;
rec->len = 200;
/* we are writing to the buff, but we are past.... */
memmove(rec->data, data, 100);
msync(base, 0, (st.st_len + rec->len), MS_ASYNC);
the struct rec_t is an example of a stuct that I want to append to the buf
and make another reccord.
If base was a regular pointer we would segfault.... cause we are past the
pointers buf....
but it kinda works.. meaning it will write and add and sometimes and not
segfault... sometimes...
or I can do this:
rec = (stuct rec_t *) base;
rec->len = 200;
memmove(rec->data, data, 100);
write(fd, (char *) rec, rec->len);
msync(base, 0, (st.st_len + rec->len), MS_ASYNC);
After I append to the file and then msync. I should be able to read the
reccord that I just added from base.
base should reflect the file.... right ?
I want to make things simple and only append to the buffer "base" and not
have to re-open the file and write to it then msync it back to mem. I know
that some of this under FreeBSD "automatic" meaning that the changes made to
the file are seen by "base" even though I do not call msync..... but in
order to keep things clear, I will msync.
I hope that this wasn't too confusing... I am not good at explanations.... or
spelling....
thank you
nathan
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