On Mon, Aug 25, 2003 at 07:15:07AM +0300, Timo Sirainen wrote:

Why did it take this long to figure out.

Write: lock(); data[0] = stuff; data[1] = stuff; unlock(); Read: do { copy = data; } while (copy[0] != copy[1]);

It's above me Timo, but well done anyway :)

C.

charlie@rubberduck.com - Melbourne, Australia http://rubberduck.com/~yeled/ PGP: 0x14AA7941 || finger yeled@lazy.spodder.com

On Mon, 25 Aug 2003, Timo Sirainen wrote:

...

Would not one rather use Maildir and assume the Kernel caches directory data? No locking contention... For read-only mailboxes it's much faster to read a single mbox file

On Monday, Aug 25, 2003, at 12:09 Europe/Helsinki, Matthias Andree wrote: than to keep opening multiple maildir files. And when you're only reading mboxes, there's no lock contention.

If a truncation occurs while concurrent processes are reading, how is this handled?

Andy

-- Andreas Aardal Hanssen

On Mon, 2003-08-25 at 15:27, Timo Sirainen wrote:

I'm actually still wondering a bit if this works. Have to ask from some people who really know. The problem is that if I write 123 over XXX, can a simultaneous read() return 1X3 in some situation? (1XX, 12X, XX3 and X23 are fine) That might break my plan..

That would probably work, but just to make sure here's an addition to the plan. Can anyone think of a situation where this would break?

While MD5 is probably good enough, it doesn't _guarantee_ the consistency. I just thought of a simple algorithm that I think would. I'll go and use that unless someone proves it wrong :)

Except of course if there's 256 writes and the last one is non-ordered and it all happens while a read() is executing.. Less than unlikely I'd say.

I don't think there's any other potential problems with read() than that it may not have all data up to date? Such as it would never temporarily show the data as zero?

static int verify(const unsigned char *buf, size_t size) { const unsigned char *checksum = buf + size; unsigned char xor; size_t i;

    xor = buf[0] ^ checksum[0];
    for (i = 1; i < size; i++) {
            if ((buf[i] ^ xor) != checksum[i])
                    return 0;
    }
    return 1;

}

void write_data(const void *data, size_t size) { unsigned char *checksum = buf + size; unsigned char xor; size_t i;

    memcpy(buf, data, size);

    checksum[0]++; // always different checksum
    xor = buf[0] ^ checksum[0];

    for (i = 1; i < size; i++)
            checksum[i] = buf[i] ^ xor;

}

void read_data(void *data, size_t size) { unsigned char copy[size*2];

    do {
            memcpy(copy, buf, size*2);
    } while (!verify(copy, size));
    memcpy(data, copy, size);

}

Timo Sirainen tss@iki.fi writes:

On Tue, 2003-08-26 at 04:40, Jens Gutzeit wrote:

...

...

messages arrived. I think this release might actually work :)

But not on my machine ;(

auth-client.c:7: auth-server-connection.h: No such file or directory

Right.. I always forget to add those .h files into Makefiles. automake should complain about them..

Run "make distdir" and configure and compile from the newly-made distdir, then you'll see what's missing from the distro.

CVS is a different matter, you'd need to cvs export to a fresh directory first to find files that have to be added.

-- Matthias Andree

Andreas Aardal Hanssen dovecot@andreas.hanssen.name writes:

On Tue, 26 Aug 2003, Matthias Andree wrote:

...

Timo Sirainen tss@iki.fi writes:

...

On Tue, 2003-08-26 at 04:40, Jens Gutzeit wrote:

...

...

messages arrived. I think this release might actually work :) But not on my machine ;( auth-client.c:7: auth-server-connection.h: No such file or directory Right.. I always forget to add those .h files into Makefiles. automake should complain about them.. Run "make distdir" and configure and compile from the newly-made distdir, then you'll see what's missing from the distro.

"make distcheck" does it all for you, if I'm not mistaken.

make distcheck does more than just that, it'll also try make dist and do a VPATH build.

-- Matthias Andree