previous change had forgot how dithering works... m(
we *really* add a random signal when *reducing* the number
of bits. just make sure we do not overflow like in
mixin().
the check in dither() was inverted. we should only
add noise when the output bit count is greater
than input bit count (samples shifted up) to
fill the lower zero bits produced by the shift.
simplifying paging code by getting rid of duppage(). instead,
fixfault() now always makes a copy of the shared/cached page
and leaves the cache alone. newpage() uncaches pages as
neccesary.
thanks charles forsyth for the suggestion.
from http://9fans.net/archive/2014/03/26:
> It isn't needed at all. When a cached page is written, it's trying hard to
> replace the page in the cache by a new copy,
> to return the previously cached page. Instead, I copy the cached page and
> return the copy, which is what it already
> does in another instance. ...
1) handle errors when loading thumbprint file.
initThumbprints() now returns nil and sets errstr
on error. a syntax error in a thumbprint file
should be reported instead of silently ignored!
(have to check users)
2) fix memory leak in initThumbprints(); we have to use
freeThumbprints() instead of free to release crltab.
3) use the actual head entries for thumbprint
storage in the thumbprints array. most thumbprint
files are rather sparse.
4) remove private emalloc() function. we shouldnt
just exit the calling process on allocation error,
instead handle error properly. this is a library!
imagereclaim() sabotaged itself by breaking the invariant
that cached pages are kept at the end of the page list.
once we made a hole of uncached pages, we would stop
reclaiming cached pages before it as the loop breaks
once it hits a uncached page. (we iterate backwards from
the tail to the head of the pagelist until pages have been
reclaimed or we hit a uncached page).
the solution is to move pages to the head of the pagelist
after removing them from the image cache.
