> "Richard B. Johnson" <root@chaos.analogic.com> writes:
>
> > This can be done in one line, with one pointer, but I will do it
> > step-by-step....
> >
> > funny struct *bits;
> > char *foo, *bar;
> > foo = (char *) malloc(WHATEVER); /* Waste 16 bits */
> > bar = foo;
> > foo += 0x00000010;
> > foo &= 0xfffffff0;
> > bits = (funny struct *) foo;
> > ........
> > do stuff
> > free(bar);
>
> Actually, that's guaranteed to waste at least one byte. The allocation of
> foo only needs to grab 15 extra bytes, and the "foo += 0x10" should
> be "foo += 0x0f" -- if foo is magically aligned to a 16-byte offset before
> you get it, then there's very little point in shifting it up to the next
> 16-byte block.
>
Picky, picky. I wouldn't really do it either way because the compiler
will not allow binary operations upon a pointer. The idea was to
demonstrate the mechanism, i.e., allocate something big enough and
do the alignment yourself.
Cheers,
Dick Johnson
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