Toob File Player checkpoint.

src/LRUCache.hpp

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+/*
+ *   Copyright (c) 2025 Robin E. R. Davies
+ *   All rights reserved.
+
+ *   Permission is hereby granted, free of charge, to any person obtaining a copy
+ *   of this software and associated documentation files (the "Software"), to deal
+ *   in the Software without restriction, including without limitation the rights
+ *   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ *   copies of the Software, and to permit persons to whom the Software is
+ *   furnished to do so, subject to the following conditions:
+ 
+ *   The above copyright notice and this permission notice shall be included in all
+ *   copies or substantial portions of the Software.
+ 
+ *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ *   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ *   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ *   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ *   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ *   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ *   SOFTWARE.
+ */
+/*
+ *   Copyright (c) 2025 Robin E. R. Davies
+ *   All rights reserved.
+
+ *   Permission is hereby granted, free of charge, to any person obtaining a copy
+ *   of this software and associated documentation files (the "Software"), to deal
+ *   in the Software without restriction, including without limitation the rights
+ *   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ *   copies of the Software, and to permit persons to whom the Software is
+ *   furnished to do so, subject to the following conditions:
+ 
+ *   The above copyright notice and this permission notice shall be included in all
+ *   copies or substantial portions of the Software.
+ 
+ *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ *   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ *   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ *   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ *   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ *   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ *   SOFTWARE.
+ */
+#pragma once 
+
+#include <unordered_map>
+#include <list>
+#include <stdexcept>
+
+template <typename KEY, typename VALUE>
+class LRUCache {
+public:
+    struct CacheNode {
+        KEY key;
+        VALUE value;
+        CacheNode(KEY k, VALUE v) : key(k), value(v) {}
+    };
+private:
+    size_t capacity;
+    std::list<CacheNode> cache_list; // Doubly-linked list for LRU order
+    std::unordered_map<KEY, typename std::list<CacheNode>::iterator> cache_map; // Map key to list iterator
+
+public:
+    explicit LRUCache(size_t cap) : capacity(cap) {
+        if (cap == 0) {
+            throw std::invalid_argument("Cache capacity must be greater than 0");
+        }
+    }
+
+    // Get value by key, return false if not found
+    bool get(const KEY& key, VALUE& value) {
+        auto it = cache_map.find(key);
+        if (it == cache_map.end()) {
+            return false;
+        }
+        // Move to front (most recently used)
+        cache_list.splice(cache_list.begin(), cache_list, it->second);
+        value = it->second->value;
+        return true;
+    }
+
+    // Put key-value pair into cache
+    void put(const KEY& key, const VALUE& value) {
+        auto it = cache_map.find(key);
+        if (it != cache_map.end()) {
+            // Update existing key
+            cache_list.splice(cache_list.begin(), cache_list, it->second);
+            it->second->value = value;
+            return;
+        }
+
+        // Add new key-value pair
+        cache_list.emplace_front(key, value);
+        cache_map[key] = cache_list.begin();
+
+        // Evict least recently used if over capacity
+        if (cache_map.size() > capacity) {
+            auto lru = cache_list.back();
+            cache_map.erase(lru.key);
+            cache_list.pop_back();
+        }
+    }
+
+    // Check if key exists
+    bool contains(const KEY& key) const {
+        return cache_map.find(key) != cache_map.end();
+    }
+
+    // Get current size
+    size_t size() const {
+        return cache_map.size();
+    }
+
+    // Get capacity
+    size_t get_capacity() const {
+        return capacity;
+    }
+    const std::list<CacheNode> &cache() const {
+        return cache_list;
+    }
+};
+