We need a better cache expiration algorithm than "make a copy of
the entire thing, sort it while holding a lock, and delete half
the items in a single burst."
Replace the Lamport clock with a double-linked list. Each insert
or lookup operation moves the affected item to the head of the list.
Each erase operation deletes one single item at the tail of the list.
Also sort out some iterator invalidation nonsense by doing erases before
inserts instead of "insert, erase, find the inserted item again because
we invalidated the found iterator during the erase."
The new implementation adds a second word-sized member to each Value
as well as a copy of the Key. Hopefully the enlarged size is not
a deal-breaker.
Signed-off-by: Zygo Blaxell <bees@furryterror.org>
check_overflow() will invalidate iterators if it decides there are too
many cache entries.
If items are deleted from the cache, search for the inserted item again
to ensure the iterator is valid.
Increase size of timestamp to size_t.
Signed-off-by: Zygo Blaxell <bees@furryterror.org>
If we release the lock first (and C++ destructor order says we do), then
the return value will be constructed from data living in an unprotected
container object. That data might be destroyed before we get to the
copy constructor for the return value.
Make a temporary copy of the return value that won't be destroyed by any
other thread, then unlock the mutex, then return the copy object.
Signed-off-by: Zygo Blaxell <bees@furryterror.org>
I'm not surprised that GCC 6 doesn't let me send an ostream ref to itself,
even inside an uninstantiated template specialization. I am a little
surprised I was trying to, and 4.9 let me get away with it.
It's 2016. auto_ptr is deprecated now.
Some things were including vector that don't any more.
https://github.com/Zygo/bees/issues/1
