On 10/28/2014 04:06 PM, Tom Lane wrote:
Heikki Linnakangas <hlinnakan...@vmware.com> writes:
It wouldn't be too hard to just do:
struct {
int64 high_bits;
uint64 low_bits;
} pg_int128;
and some macros for the + - etc. operators. It might be less work than
trying to deal with the portability issues of a native C datatype for this.
-1. That's not that easy, especially for division, or if you want to
worry about overflow.
The patch doesn't do division with the 128-bit integers. It only does
addition and multiplication. Those are pretty straightforward to implement.
The point of this patch IMO is to get some low
hanging fruit; coding our own int128 arithmetic doesn't sound like
"low hanging" to me.
I wasn't thinking of writing a full-fledged 128-bit type, just the the
few operations needed for this patch.
Also, we've already got the configure infrastructure for detecting
whether a platform has working int64. It really shouldn't be much
work to transpose that to int128 (especially if we don't care about
printf support, which I think we don't).
It would be nicer to be able to use the same code on all platforms. With
a configure test, we'd still need a fallback implementation for
platforms that don't have it.
- Heikki
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