This is a reasonably conservative increase in the number of buckets in the hash
table to 251. After FcInit(), there are 240 shared strings in use on my system
(from configuration files I assume). The hash value is stored in each link in
the chains so comparison are actually not very expensive. This change should
reduce the average length of chains by a factor of 8. With the reference
counted strings, it should keep the average length of chains to about 2. The
number of buckets is prime so as not to rely too much on the quality of the
hash function.
https://bugs.freedesktop.org/show_bug.cgi?id=17832#c5
Patch from Karl Tomlinson
I noticed that Qt always uses a different font than fc-match advertises.
Debugging the issue, I found that a call that looks pretty innocent is
changing all weak bindings to strong bindings and as such changes the
semantic of the match: FcPatternDuplicate.
The union inside the FcValue structure contains pad bytes. Instead of
copying the whole structure to the cache block, copy only the initialized
fields to avoid writing whichever bytes serve as padding within the
structure.
Using a simple shell script that processes the public headers, two header
files are constructed that map public symbols to hidden internal aliases
avoiding the assocated PLT entry for referring to a public symbol.
A few mistakes in the FcPrivate/FcPublic annotations were also discovered
through this process
Caches contain patterns and character sets which are reference counted and
visible to applications. Reference count the underlying cache object so that
it stays around until all reference objects are no longer in use.
This is less efficient than just leaving all caches around forever, but does
avoid eternal size increases in case applications ever bother to actually
look for changes in the font configuration.
Instead of passing directory information around in separate variables,
collect it all in an FcCache structure. Numerous internal and tool
interfaces changed as a result of this.
Charsets are now pre-frozen before being serialized. This causes them to
share across multiple fonts in the same cache.
Eliminate ancient list of object name databases and load names into single
hash table that includes type information. Typecheck all pattern values to
avoid mis-typed pattern elements.
FcCharSetSerialize was computing the offset to the unserialized leaf,
which left it pointing at random data when the cache was reloaded.
fc-cat has been updated to work with the new cache structure.
Various debug messages extended to help diagnose serialization errors.
Replace all of the bank/id pairs with simple offsets, recode several
data structures to always use offsets inside the library to avoid
conditional paths. Exposed data structures use pointers to hold offsets,
setting the low bit to distinguish between offset and pointer.
Use offset-based data structures for lang charset encodings; eliminates
separate data structure format for that file.
Much testing will be needed; offsets are likely not detected everywhere in
the library yet.
permitting cache files to be stored in font dirs. Bump cache magic.
Don't include /fonts.cache-2 in cache hash construction.
reviewed by: Patrick Lam <plam@mit.edu>
Minor change to global cache file format to fix fc-cat bug reported by
Frederic Crozat, and buglet with not globally caching directories with
zero fonts cached.
Check for type validity during FcPatternAddWithBinding, don't verify type
in FcFontMatch, don't call FcCanonicalize here (which always does a
deep copy).
reviewed by: plam
Akira TAGOH
Behdad Esfahbod
Keith Packard
Stephan Kulow
Keith Packard
Patrick Lam