This patch adds a hashtable-based LRU cache. This should be
significantly higher performance than the GenerationCache it is intended
to replace. It is a large part of the fix for bug 7271109
TextLayoutCache low-level performance issues.
We added a new method to BasicHashtable to detect when rehashing is
needed, because the internal linked list pointers would get invalidated
by that rehashing.
Also, the hash_type specialized to pointers had a small flaw.
Change-Id: I950c2083f96519777b851dbe157100e0a334caec
The basic hashtable is intended to be used to support a variety
of different datastructures such as map, set, multimap,
multiset, linkedmap, generationcache, etc.
Consequently its interface is fairly primitive.
The basic hashtable supports copy-on-write style functionality
using SharedBuffer.
The change introduces a simple generic function in TypeHelpers for
specifying hash functions. The idea is to add template
specializations of hash_type<T> next to the relevant data structures
such as String8, String16, sp<T>, etc.
Change-Id: I2c479229e9d4527b4fbfe3b8b04776a2fd32c973
