抛弃GdCpp*.dll/pdb历史重新建库。libhv和Sqlite的dll保留
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Zhang Jianjun
312
include/hv/LRUCache.h
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312
include/hv/LRUCache.h
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#ifndef HV_LRU_CACHE_H_
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#define HV_LRU_CACHE_H_
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#include <unordered_map>
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#include <list>
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#include <mutex>
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#include <memory>
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#include <functional>
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namespace hv {
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/**
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* @brief Thread-safe LRU (Least Recently Used) Cache template
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*
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* This template provides a generic LRU cache implementation with the following features:
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* - Thread-safe operations using mutex
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* - Configurable capacity with automatic eviction
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* - O(1) get, put, and remove operations
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* - Optional eviction callback for cleanup
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*
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* @tparam Key The key type (must be hashable)
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* @tparam Value The value type
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*/
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template<typename Key, typename Value>
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class LRUCache {
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public:
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using key_type = Key;
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using value_type = Value;
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using eviction_callback_t = std::function<void(const Key&, const Value&)>;
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private:
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// Double-linked list node for LRU ordering
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struct Node {
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Key key;
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Value value;
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Node(const Key& k, const Value& v) : key(k), value(v) {}
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};
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using node_list_t = std::list<Node>;
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using node_iterator_t = typename node_list_t::iterator;
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using hash_map_t = std::unordered_map<Key, node_iterator_t>;
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public:
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/**
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* @brief Construct LRUCache with specified capacity
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* @param capacity Maximum number of items to cache (default: 100)
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*/
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explicit LRUCache(size_t capacity = 100)
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: capacity_(capacity), eviction_callback_(nullptr) {
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if (capacity_ == 0) {
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capacity_ = 1; // Minimum capacity of 1
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}
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}
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/**
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* @brief Destructor
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*/
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virtual ~LRUCache() {
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clear();
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}
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// Disable copy constructor and assignment operator
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LRUCache(const LRUCache&) = delete;
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LRUCache& operator=(const LRUCache&) = delete;
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/**
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* @brief Set eviction callback function
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* @param callback Function to call when items are evicted
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*/
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void set_eviction_callback(eviction_callback_t callback) {
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std::lock_guard<std::mutex> lock(mutex_);
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eviction_callback_ = callback;
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}
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/**
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* @brief Get value by key
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* @param key The key to search for
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* @param value Output parameter for the value
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* @return true if key exists, false otherwise
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*/
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bool get(const Key& key, Value& value) {
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std::lock_guard<std::mutex> lock(mutex_);
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auto it = hash_map_.find(key);
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if (it == hash_map_.end()) {
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return false;
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}
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// Move to front (most recently used)
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move_to_front(it->second);
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value = it->second->value;
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return true;
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}
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/**
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* @brief Get value by key (alternative interface)
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* @param key The key to search for
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* @return Pointer to value if exists, nullptr otherwise
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*/
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Value* get(const Key& key) {
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std::lock_guard<std::mutex> lock(mutex_);
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auto it = hash_map_.find(key);
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if (it == hash_map_.end()) {
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return nullptr;
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}
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// Move to front (most recently used)
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move_to_front(it->second);
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return &(it->second->value);
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}
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/**
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* @brief Put key-value pair into cache
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* @param key The key
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* @param value The value
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* @return true if new item was added, false if existing item was updated
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*/
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bool put(const Key& key, const Value& value) {
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std::lock_guard<std::mutex> lock(mutex_);
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auto it = hash_map_.find(key);
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if (it != hash_map_.end()) {
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// Update existing item
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it->second->value = value;
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move_to_front(it->second);
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return false;
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}
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// Add new item
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if (node_list_.size() >= capacity_) {
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evict_lru();
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}
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node_list_.emplace_front(key, value);
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hash_map_[key] = node_list_.begin();
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return true;
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}
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/**
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* @brief Remove item by key
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* @param key The key to remove
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* @return true if item was removed, false if key not found
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*/
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bool remove(const Key& key) {
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std::lock_guard<std::mutex> lock(mutex_);
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auto it = hash_map_.find(key);
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if (it == hash_map_.end()) {
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return false;
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}
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// Call eviction callback if set
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if (eviction_callback_) {
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eviction_callback_(it->second->key, it->second->value);
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}
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node_list_.erase(it->second);
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hash_map_.erase(it);
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return true;
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}
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/**
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* @brief Check if key exists in cache
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* @param key The key to check
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* @return true if key exists, false otherwise
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*/
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bool contains(const Key& key) const {
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std::lock_guard<std::mutex> lock(mutex_);
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return hash_map_.find(key) != hash_map_.end();
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}
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/**
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* @brief Clear all items from cache
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*/
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void clear() {
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std::lock_guard<std::mutex> lock(mutex_);
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if (eviction_callback_) {
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for (const auto& node : node_list_) {
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eviction_callback_(node.key, node.value);
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}
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}
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node_list_.clear();
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hash_map_.clear();
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}
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/**
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* @brief Get current cache size
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* @return Number of items in cache
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*/
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size_t size() const {
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std::lock_guard<std::mutex> lock(mutex_);
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return node_list_.size();
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}
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/**
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* @brief Get cache capacity
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* @return Maximum number of items cache can hold
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*/
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size_t capacity() const {
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return capacity_;
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}
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/**
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* @brief Check if cache is empty
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* @return true if cache is empty, false otherwise
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*/
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bool empty() const {
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std::lock_guard<std::mutex> lock(mutex_);
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return node_list_.empty();
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}
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/**
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* @brief Set new capacity (may trigger eviction)
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* @param new_capacity New capacity value
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*/
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void set_capacity(size_t new_capacity) {
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if (new_capacity == 0) {
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new_capacity = 1; // Minimum capacity of 1
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}
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std::lock_guard<std::mutex> lock(mutex_);
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capacity_ = new_capacity;
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// Evict excess items if necessary
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while (node_list_.size() > capacity_) {
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evict_lru();
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}
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}
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/**
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* @brief Apply a function to all cached items (for iteration)
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* @param func Function to apply to each key-value pair
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* Note: This is provided for compatibility but should be used carefully
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* as it may affect performance due to locking
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*/
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template<typename Func>
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void for_each(Func func) {
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std::lock_guard<std::mutex> lock(mutex_);
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for (const auto& node : node_list_) {
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func(node.key, node.value);
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}
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}
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/**
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* @brief Remove items that match a predicate
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* @param predicate Function that returns true for items to remove
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* @return Number of items removed
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*/
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template<typename Predicate>
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size_t remove_if(Predicate predicate) {
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std::lock_guard<std::mutex> lock(mutex_);
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size_t removed_count = 0;
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auto it = node_list_.begin();
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while (it != node_list_.end()) {
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if (predicate(it->key, it->value)) {
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// Call eviction callback if set
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if (eviction_callback_) {
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eviction_callback_(it->key, it->value);
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}
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hash_map_.erase(it->key);
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it = node_list_.erase(it);
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removed_count++;
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} else {
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++it;
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}
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}
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return removed_count;
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}
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protected:
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/**
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* @brief Move node to front of list (most recently used position)
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* @param it Iterator to the node to move
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*/
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void move_to_front(node_iterator_t it) {
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if (it != node_list_.begin()) {
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node_list_.splice(node_list_.begin(), node_list_, it);
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}
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}
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/**
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* @brief Evict least recently used item
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*/
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void evict_lru() {
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if (node_list_.empty()) {
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return;
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}
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auto last = std::prev(node_list_.end());
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// Call eviction callback if set
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if (eviction_callback_) {
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eviction_callback_(last->key, last->value);
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}
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hash_map_.erase(last->key);
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node_list_.erase(last);
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}
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protected:
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size_t capacity_; // Maximum cache capacity
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mutable std::mutex mutex_; // Mutex for thread safety
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node_list_t node_list_; // Doubly-linked list for LRU ordering
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hash_map_t hash_map_; // Hash map for O(1) access
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eviction_callback_t eviction_callback_; // Optional eviction callback
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};
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} // namespace hv
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#endif // HV_LRU_CACHE_H_
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