diff -r 3d4e9c994f10 -r a86126ab1dd4 wp/wp-includes/sitemaps/class-wp-sitemaps-registry.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/sitemaps/class-wp-sitemaps-registry.php	Tue Dec 15 13:49:49 2020 +0100
@@ -0,0 +1,85 @@
+<?php
+/**
+ * Sitemaps: WP_Sitemaps_Registry class
+ *
+ * Handles registering sitemap providers.
+ *
+ * @package WordPress
+ * @subpackage Sitemaps
+ * @since 5.5.0
+ */
+
+/**
+ * Class WP_Sitemaps_Registry.
+ *
+ * @since 5.5.0
+ */
+class WP_Sitemaps_Registry {
+	/**
+	 * Registered sitemap providers.
+	 *
+	 * @since 5.5.0
+	 *
+	 * @var WP_Sitemaps_Provider[] Array of registered sitemap providers.
+	 */
+	private $providers = array();
+
+	/**
+	 * Adds a new sitemap provider.
+	 *
+	 * @since 5.5.0
+	 *
+	 * @param string               $name     Name of the sitemap provider.
+	 * @param WP_Sitemaps_Provider $provider Instance of a WP_Sitemaps_Provider.
+	 * @return bool Whether the provider was added successfully.
+	 */
+	public function add_provider( $name, WP_Sitemaps_Provider $provider ) {
+		if ( isset( $this->providers[ $name ] ) ) {
+			return false;
+		}
+
+		/**
+		 * Filters the sitemap provider before it is added.
+		 *
+		 * @since 5.5.0
+		 *
+		 * @param WP_Sitemaps_Provider $provider Instance of a WP_Sitemaps_Provider.
+		 * @param string               $name     Name of the sitemap provider.
+		 */
+		$provider = apply_filters( 'wp_sitemaps_add_provider', $provider, $name );
+		if ( ! $provider instanceof WP_Sitemaps_Provider ) {
+			return false;
+		}
+
+		$this->providers[ $name ] = $provider;
+
+		return true;
+	}
+
+	/**
+	 * Returns a single registered sitemap provider.
+	 *
+	 * @since 5.5.0
+	 *
+	 * @param string $name Sitemap provider name.
+	 * @return WP_Sitemaps_Provider|null Sitemap provider if it exists, null otherwise.
+	 */
+	public function get_provider( $name ) {
+		if ( ! isset( $this->providers[ $name ] ) ) {
+			return null;
+		}
+
+		return $this->providers[ $name ];
+	}
+
+	/**
+	 * Returns all registered sitemap providers.
+	 *
+	 * @since 5.5.0
+	 *
+	 * @return WP_Sitemaps_Provider[] Array of sitemap providers.
+	 */
+	public function get_providers() {
+		return $this->providers;
+	}
+}