PHP Class MatthiasMullie\Scrapbook\Buffered\Utils\Buffer
The memory-part can easily be handled by MemoryStore. There's just 1 gotcha:
when an item is to be deleted (but not yet committed), it needs to be deleted
from the MemoryStore too, but we need to be able to make a distinction
between "this is deleted" and "this value is not known in this memory cache,
fall back to real cache".
This is where this class comes in to play: we'll add an additional "expired"
method, which allows BufferedStore to just expire the keys that are supposed
to be deleted (instead of deleting them) - then we can keep track of when
a key is just not known, or known-but-deleted (=expired)
Checks if a value exists in cache and is not yet expired.
Method Details
exists()
protectedmethod
Contrary to default MemoryStore, expired items must *not* be deleted
from memory: we need to remember that they were expired, so we don't
reach out to real cache (only to get nothing, since it's expired...).
Because our local buffer is also just a real cache, expired items will
just return nothing, which will lead us to believe no such item exists in
that local cache, and we'll reach out to the real cache (where the value
may not yet have been expired because that may have been part of an
uncommitted write)
So we'll want to know when a value is in local cache, but expired!
