MapCacheLRU.php

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<?php
use Wikimedia\Assert\Assert;
 
class MapCacheLRU {
    protected $cache = []; // (key => value)
 
    protected $maxCacheKeys; // integer; max entries
 
    public function __construct( $maxKeys ) {
        Assert::parameterType( 'integer', $maxKeys, '$maxKeys' );
        Assert::parameter( $maxKeys > 0, '$maxKeys', 'must be above zero' );
 
        $this->maxCacheKeys = $maxKeys;
    }
 
    public function set( $key, $value ) {
        if ( $this->has( $key ) ) {
            $this->ping( $key );
        } elseif ( count( $this->cache ) >= $this->maxCacheKeys ) {
            reset( $this->cache );
            $evictKey = key( $this->cache );
            unset( $this->cache[$evictKey] );
        }
        $this->cache[$key] = $value;
    }
 
    public function has( $key ) {
        if ( !is_int( $key ) && !is_string( $key ) ) {
            throw new MWException( __METHOD__ . ' called with invalid key. Must be string or integer.' );
        }
        return array_key_exists( $key, $this->cache );
    }
 
    public function get( $key ) {
        if ( !$this->has( $key ) ) {
            return null;
        }
 
        $this->ping( $key );
 
        return $this->cache[$key];
    }
 
    public function getAllKeys() {
        return array_keys( $this->cache );
    }
 
    public function getWithSetCallback( $key, callable $callback ) {
        if ( $this->has( $key ) ) {
            $value = $this->get( $key );
        } else {
            $value = call_user_func( $callback );
            if ( $value !== false ) {
                $this->set( $key, $value );
            }
        }
 
        return $value;
    }
 
    public function clear( $keys = null ) {
        if ( $keys === null ) {
            $this->cache = [];
        } else {
            foreach ( (array)$keys as $key ) {
                unset( $this->cache[$key] );
            }
        }
    }
 
    protected function ping( $key ) {
        $item = $this->cache[$key];
        unset( $this->cache[$key] );
        $this->cache[$key] = $item;
    }
}