Saturating integer arithmetic

[Manu via Digitalmars-d]

Hi people. I've been working on this colour library when I have free
time (almost never!), and I want to work on blending/filtering
functions, but that work is kinda blocked by saturating arithmetic
logic.
I started working on a saturating integer library a few times, but
it's much a much bigger job than it appears, and I haven't had enough
time for it. (Efficient) implementation tends to be significantly
different for every int width and signed/unsigned. I see no use for an
inefficient implementation used by a colour library; images tend to be
millions of pixels, and inefficiency very quickly adds up.

I wonder if anyone has an interest in the area and wants to have a go
at it? It's a pretty big job.
It should support scalars, packed vectors (ie, 4 bytes in an int), and
SIMD vectors (wider vectors using hardware simd ops). Each step can
gain considerable efficiency for the vector width. It's hard to write
a useful colour blending library without the full set of these
available.