LRUCache< Key, Value, MaxSize > Class Template Reference

A simple LRU (Least Recently Used) cache with a fixed maximum size. More...

#include <gin_lrucache.h>

Public Member Functions
	LRUCache ()=default
	Creates an empty LRU cache.
Value *	get (const Key &key)
	Returns a pointer to the cached value for the given key, or nullptr if not found.
const Value *	get (const Key &key) const
	Returns a const pointer to the cached value for the given key, or nullptr if not found.
void	put (const Key &key, Value value)
	Inserts or updates a value in the cache.
template<typename Factory >
Value &	getOrCreate (const Key &key, Factory &&factory)
	Gets an existing value or creates a new one using the provided factory function.
bool	remove (const Key &key)
	Removes an item from the cache.
bool	contains (const Key &key) const
	Checks if a key exists in the cache.
size_t	size () const noexcept
	Returns the number of items currently in the cache.
bool	empty () const noexcept
	Checks if the cache is empty.
void	clear ()
	Removes all items from the cache.

Static Public Member Functions
static constexpr size_t	maxSize () noexcept
	Returns the maximum number of items the cache can hold.

Detailed Description

template<typename Key, typename Value, size_t MaxSize>
class LRUCache< Key, Value, MaxSize >

A simple LRU (Least Recently Used) cache with a fixed maximum size.

This template class provides a cache that automatically evicts the least recently accessed items when it reaches capacity. It uses a hash map for O(1) average-case lookups and a linked list to track access order.

The cache is not thread-safe. If you need thread safety, you should synchronize access externally.

Example usage:

LRUCache<juce::String, int, 10> cache;
 
// Insert items
cache.put ("one", 1);
cache.put ("two", 2);
 
// Retrieve items
if (auto* value = cache.get ("one"))
    process (*value);
 
// Use getOrCreate for lazy initialization
auto& value = cache.getOrCreate ("three", [] { return expensiveComputation(); });

Template Parameters

Key	The type used as the cache key. Must be hashable via std::hash.
Value	The type of values stored in the cache.
MaxSize	The maximum number of items the cache can hold.

Constructor & Destructor Documentation

LRUCache()

template<typename Key , typename Value , size_t MaxSize>

LRUCache< Key, Value, MaxSize >::LRUCache ( )

default

Creates an empty LRU cache.

Member Function Documentation

get() [1/2]

template<typename Key , typename Value , size_t MaxSize>

Value * LRUCache< Key, Value, MaxSize >::get

(

const Key &

key

)

Returns a pointer to the cached value for the given key, or nullptr if not found.

Accessing an item moves it to the front of the cache (most recently used).

Parameters

key	The key to look up

Returns

A pointer to the value if found, nullptr otherwise

Referenced by LRUCache< Key, Value, MaxSize >::get(), and LRUCache< Key, Value, MaxSize >::getOrCreate().

get() [2/2]

template<typename Key , typename Value , size_t MaxSize>

const Value * LRUCache< Key, Value, MaxSize >::get

(

const Key &

key

)

const

Returns a const pointer to the cached value for the given key, or nullptr if not found.

Accessing an item moves it to the front of the cache (most recently used).

Parameters

key	The key to look up

Returns

A const pointer to the value if found, nullptr otherwise

References LRUCache< Key, Value, MaxSize >::get().

put()

template<typename Key , typename Value , size_t MaxSize>

void LRUCache< Key, Value, MaxSize >::put	(	const Key &	key,
		Value	value
	)

Inserts or updates a value in the cache.

If the key already exists, its value is updated and it's moved to the front. If the cache is at capacity, the least recently used item is evicted.

Parameters

key	The key to insert or update
value	The value to store

Referenced by LRUCache< Key, Value, MaxSize >::getOrCreate().

getOrCreate()

template<typename Key , typename Value , size_t MaxSize>

template<typename Factory >

Value & LRUCache< Key, Value, MaxSize >::getOrCreate	(	const Key &	key,
		Factory &&	factory
	)

Gets an existing value or creates a new one using the provided factory function.

If the key exists, returns a reference to its value (moving it to front). If the key doesn't exist, calls the factory function to create a value, inserts it, and returns a reference to it.

Parameters

key	The key to look up or create
factory	A callable that takes no arguments and returns a Value

Returns

A reference to the cached value

References LRUCache< Key, Value, MaxSize >::get(), and LRUCache< Key, Value, MaxSize >::put().

remove()

template<typename Key , typename Value , size_t MaxSize>

bool LRUCache< Key, Value, MaxSize >::remove

(

const Key &

key

)

Removes an item from the cache.

Parameters

key	The key to remove

Returns

true if the item was found and removed, false otherwise

contains()

template<typename Key , typename Value , size_t MaxSize>

bool LRUCache< Key, Value, MaxSize >::contains

(

const Key &

key

)

const

Checks if a key exists in the cache.

Note: This does NOT update the access order.

Parameters

key	The key to check

Returns

true if the key exists, false otherwise

size()

template<typename Key , typename Value , size_t MaxSize>

size_t LRUCache< Key, Value, MaxSize >::size ( ) const

noexcept

Returns the number of items currently in the cache.

Returns

The current size of the cache

empty()

template<typename Key , typename Value , size_t MaxSize>

bool LRUCache< Key, Value, MaxSize >::empty ( ) const

noexcept

Checks if the cache is empty.

Returns

true if the cache contains no items

clear()

template<typename Key , typename Value , size_t MaxSize>

void LRUCache< Key, Value, MaxSize >::clear

(

)

Removes all items from the cache.

maxSize()

template<typename Key , typename Value , size_t MaxSize>

static constexpr size_t LRUCache< Key, Value, MaxSize >::maxSize ( )

staticconstexprnoexcept

Returns the maximum number of items the cache can hold.

Returns

The maximum capacity

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The documentation for this class was generated from the following file:

• gin_lrucache.h