RE: nonstandard assumptions in the code

["Howard Chu" <hyc@highlandsun.com>]

> -----Original Message-----
> From: Hallvard B Furuseth [mailto:h.b.furuseth@usit.uio.no]

> Kurt D. Zeilenga writes:
> >At 11:01 AM 5/30/2003, Hallvard B Furuseth wrote:
> >>
> >> Here are the nonstandard assumptions I have found.
> >> (...)
> 
> 
> >> * no padding bits in 'unsigned int'
> >>   (required by back-bdb/dbcache.c:bdb_db_hash() - don't know why)
> >> (...)
> > These should be fixed.
> 
> Howard, this is your code, from when you fixed ITS#1726.  Something
> about endianness, perhaps?  If not, we can use this function body,
> roughly from my original patch.  I have dropped the ugly if-test for
> whether or not memcpy can be used, since I doubt the code is 
> that time-
> critical.
> 
> {
> 	u_int32_t i, ret = 0;
> 
> 	if ( length > sizeof(u_int32_t) )
> 		length = sizeof(u_int32_t);
> 
> 	for( i = 0; i < length; i++ )
> 		ret = (ret << 8) + ((const unsigned char *)bytes)[i];
> 	return ret;
> }

This code reverses the byte-order of the hash on little-endian machines,
which makes the hash databases in HEAD incompatible with RE22.

I note that the BDB configure script demands that sizeof(u_int32_t) == 4,
so I don't see any point in accomodating padding bits here. Whether they
exist or not at the machine level should be invisible at the C level, if
the compiler is going to claim that sizeof(u_int32_t) == 4. I think the
previous code was perfectly fine and we should revert.

  -- Howard Chu
  Chief Architect, Symas Corp.       Director, Highland Sun
  http://www.symas.com               http://highlandsun.com/hyc
  Symas: Premier OpenSource Development and Support