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vendor/yiisoft/yii2/caching/Dependency.php

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+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\caching;
+
+/**
+ * Dependency is the base class for cache dependency classes.
+ *
+ * Child classes should override its [[generateDependencyData()]] for generating
+ * the actual dependency data.
+ *
+ * For more details and usage information on Cache, see the [guide article on caching](guide:caching-overview).
+ *
+ * @author Qiang Xue <qiang.xue@gmail.com>
+ * @since 2.0
+ */
+abstract class Dependency extends \yii\base\BaseObject
+{
+    /**
+     * @var mixed the dependency data that is saved in cache and later is compared with the
+     * latest dependency data.
+     */
+    public $data;
+    /**
+     * @var bool whether this dependency is reusable or not. True value means that dependent
+     * data for this cache dependency will be generated only once per request. This allows you
+     * to use the same cache dependency for multiple separate cache calls while generating the same
+     * page without an overhead of re-evaluating dependency data each time. Defaults to false.
+     */
+    public $reusable = false;
+
+    /**
+     * @var array static storage of cached data for reusable dependencies.
+     */
+    private static $_reusableData = [];
+
+
+    /**
+     * Evaluates the dependency by generating and saving the data related with dependency.
+     * This method is invoked by cache before writing data into it.
+     * @param CacheInterface $cache the cache component that is currently evaluating this dependency
+     */
+    public function evaluateDependency($cache)
+    {
+        if ($this->reusable) {
+            $hash = $this->generateReusableHash();
+            if (!array_key_exists($hash, self::$_reusableData)) {
+                self::$_reusableData[$hash] = $this->generateDependencyData($cache);
+            }
+            $this->data = self::$_reusableData[$hash];
+        } else {
+            $this->data = $this->generateDependencyData($cache);
+        }
+    }
+
+    /**
+     * Returns a value indicating whether the dependency has changed.
+     * @deprecated since version 2.0.11. Will be removed in version 2.1. Use [[isChanged()]] instead.
+     * @param CacheInterface $cache the cache component that is currently evaluating this dependency
+     * @return bool whether the dependency has changed.
+     */
+    public function getHasChanged($cache)
+    {
+        return $this->isChanged($cache);
+    }
+
+    /**
+     * Checks whether the dependency is changed.
+     * @param CacheInterface $cache the cache component that is currently evaluating this dependency
+     * @return bool whether the dependency has changed.
+     * @since 2.0.11
+     */
+    public function isChanged($cache)
+    {
+        if ($this->reusable) {
+            $hash = $this->generateReusableHash();
+            if (!array_key_exists($hash, self::$_reusableData)) {
+                self::$_reusableData[$hash] = $this->generateDependencyData($cache);
+            }
+            $data = self::$_reusableData[$hash];
+        } else {
+            $data = $this->generateDependencyData($cache);
+        }
+
+        return $data !== $this->data;
+    }
+
+    /**
+     * Resets all cached data for reusable dependencies.
+     */
+    public static function resetReusableData()
+    {
+        self::$_reusableData = [];
+    }
+
+    /**
+     * Generates a unique hash that can be used for retrieving reusable dependency data.
+     * @return string a unique hash value for this cache dependency.
+     * @see reusable
+     */
+    protected function generateReusableHash()
+    {
+        $data = $this->data;
+        $this->data = null;  // https://github.com/yiisoft/yii2/issues/3052
+        $key = sha1(serialize($this));
+        $this->data = $data;
+        return $key;
+    }
+
+    /**
+     * Generates the data needed to determine if dependency is changed.
+     * Derived classes should override this method to generate the actual dependency data.
+     * @param CacheInterface $cache the cache component that is currently evaluating this dependency
+     * @return mixed the data needed to determine if dependency has been changed.
+     */
+    abstract protected function generateDependencyData($cache);
+}