LRUCache.php

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<?php

namespace Elgg\Cache;

use Elgg\Exceptions\RangeException;

class LRUCache implements \ArrayAccess {
    
    protected $maximumSize;

    protected $data = [];

    public function __construct(int $size) {
        if ($size <= 0) {
            throw new RangeException('"size" must be greater than 0');
        }
        
        $this->maximumSize = $size;
    }

    public function get($key, $default = null) {
        if ($this->containsKey($key)) {
            $this->recordAccess($key);
            
            return $this->data[$key];
        }
        
        return $default;
    }

    public function set($key, $value) {
        if ($this->containsKey($key)) {
            $this->data[$key] = $value;
            $this->recordAccess($key);
        } else {
            $this->data[$key] = $value;
            if ($this->size() > $this->maximumSize) {
                // remove least recently used element (front of array)
                reset($this->data);
                unset($this->data[key($this->data)]);
            }
        }
    }

    public function size() {
        return count($this->data);
    }

    public function containsKey($key) {
        return array_key_exists($key, $this->data);
    }

    public function remove($key) {
        if ($this->containsKey($key)) {
            $value = $this->data[$key];
            unset($this->data[$key]);
            return $value;
        }
        
        return null;
    }

    public function clear() {
        $this->data = [];
    }

    protected function recordAccess($key) {
        $value = $this->data[$key];
        unset($this->data[$key]);
        $this->data[$key] = $value;
    }

    #[\ReturnTypeWillChange]
    public function offsetSet($offset, $value) {
        $this->set($offset, $value);
    }

    #[\ReturnTypeWillChange]
    public function offsetGet($offset) {
        return $this->get($offset);
    }

    #[\ReturnTypeWillChange]
    public function offsetUnset($offset) {
        $this->remove($offset);
    }

    #[\ReturnTypeWillChange]
    public function offsetExists($offset) {
        return $this->containsKey($offset);
    }
}