Templated synchronized unordered map as a least-recently-used cache
The data structure interface is defined as follows
template<typename Key, typename Value>
class SynchronizedLRUCacheMap
{
public:
SynchronizedLRUCacheMap(size_t max_elems = 10);
// main modifier methods
bool insert(Key, Value);
bool update(Key, Value);
bool has(Key);
Value access(Key);
void resize(size_t);
// inspection/debugging methods
size_t size() const;
std::list<Key> cacheKeyState(void) const;
void printState();
}
Implmementation is contained in lru.hpp, a small suite of test/examples is in main.cpp.
Possible main program output:
--- simpleTest() ---
Initializing cache with max elems = 3
Inserting {1, "foo"} ...
Inserting {2, "bar"} ...
Current cache state: {2: bar}, {1: foo},
cache.access(1) = foo
Current cache state: {1: foo}, {2: bar},
Inserting {3, "asdf"} ...
Accessing Key=2 ...
Inserting {4, "qwer"} ...
Current cache state: {4: qwer}, {2: bar}, {3: asdf},
cache.access(3) = asdf
Resizing cache to max elems = 1 ...
Updating value keyed by 3 ...
Current cache state: {3: zxcv},
--- ptrTest() ---
Initializing cache with max elems = 3
Inserting {"one", *SomeCachedObject(1)} ...
Inserting {"two", *SomeCachedObject(10)} ...
*cache.access("one") = SomeCachedObject<id=1>
Current cache state: {one: 0x600002aa8218}, {two: 0x600002aa81d8},
Inserting {"three", *SomeCachedObject(11)} ...
Inserting {"four", *SomeCachedObject(100)} ...
*cache.access("one") = SomeCachedObject<id=1>
Key "two" no longer in cache!
Current cache state: {one: 0x600002aa8218}, {four: 0x600002aa8318}, {three: 0x600002aa8298},
--- threadedTest() ---
Initializing cache with max elems = 2
Inserting "t1" ...
Inserting "t2" ...
Inserting "t3" ...
Current cache state: {t2: 0x16bc5f000}, {t3: 0x16bceb000},
Accessing keys "t2", "t3" in separate threads ...
Current cache state: {t2: 0x16bc5f000}, {t3: 0x16bceb000},