jetpack 5.3

Signed-off-by: Anthony G. Basile <blueness@gentoo.org>

15 files changed, 996 insertions, 387 deletions

diff --git a/plugins/jetpack/modules/sitemaps/sitemap-buffer-fallback.php b/plugins/jetpack/modules/sitemaps/sitemap-buffer-fallback.php
new file mode 100644
index 00000000..1cf73c09
--- /dev/null
+++ b/plugins/jetpack/modules/sitemaps/sitemap-buffer-fallback.php
@@ -0,0 +1,146 @@
+<?php
+/**
+ * The fallback buffer for users with no XML support.
+ *
+ * @since 5.3.0
+ * @package Jetpack
+ */
+
+/**
+ * A buffer for constructing master sitemap xml files.
+ *
+ * @since 5.1.0
+ */
+abstract class Jetpack_Sitemap_Buffer_Fallback extends Jetpack_Sitemap_Buffer {
+
+	/**
+	 * The buffer contents.
+	 *
+	 * @access protected
+	 * @since 5.3.0
+	 * @var string The buffer contents.
+	 */
+	protected $buffer;
+
+	public function __construct( $item_limit, $byte_limit, $time = '1970-01-01 00:00:00' ) {
+		$this->is_full_flag = false;
+		$this->is_empty_flag = true;
+		$this->timestamp = $time;
+
+		$this->finder = new Jetpack_Sitemap_Finder();
+
+		$this->item_capacity = max( 1, intval( $item_limit ) );
+		$this->byte_capacity = max( 1, intval( $byte_limit ) ) - strlen( $this->contents() );
+	}
+
+	/**
+	 * Append an item to the buffer, if there is room for it,
+	 * and set is_empty_flag to false. If there is no room,
+	 * we set is_full_flag to true. If $item is null,
+	 * don't do anything and report success.
+	 *
+	 * @since 5.3.0
+	 *
+	 * @param array $array The item to be added.
+	 *
+	 * @return bool True if the append succeeded, False if not.
+	 */
+	public function append( $array ) {
+		if ( is_null( $array ) ) {
+			return true;
+		}
+
+		if ( $this->is_full_flag ) {
+			return false;
+		}
+
+		if ( 0 >= $this->item_capacity || 0 >= $this->byte_capacity ) {
+			$this->is_full_flag = true;
+			return false;
+		} else {
+			$this->item_capacity -= 1;
+			$added_string = $this->array_to_xml_string( $array );
+			$this->buffer .= $added_string;
+			$this->is_empty_flag = false;
+
+			mbstring_binary_safe_encoding(); // So we can safely use strlen().
+			$this->byte_capacity -= strlen( $added_string );
+			reset_mbstring_encoding();
+
+			return true;
+		}
+	}
+
+	/**
+	 * Detect whether the buffer is empty.
+	 *
+	 * @since 5.3.0
+	 *
+	 * @return bool True if the buffer is empty, false otherwise.
+	 */
+	public function is_empty() {
+		return $this->is_empty_flag;
+	}
+
+	/**
+	 * Retrieve the contents of the buffer.
+	 *
+	 * @since 5.3.0
+	 *
+	 * @return string The contents of the buffer (with the footer included).
+	 */
+	public function contents() {
+		$root = $this->get_root_element();
+
+		return '<?xml version="1.0" encoding="UTF-8"?>' . PHP_EOL . $root[0] . $this->buffer . $root[1] . PHP_EOL;
+	}
+
+	/**
+	 * Legacy implementation of array to XML conversion without using DOMDocument.
+	 *
+	 * @param Array $array
+	 * @return String $result
+	 */
+	public function array_to_xml_string( $array, $parent = null, $root = null ) {
+		$string = '';
+
+		foreach ( $array as $key => $value ) {
+			// Only allow a-z, A-Z, colon, underscore, and hyphen.
+			$tag = preg_replace( '/[^a-zA-Z:_-]/', '_', $key );
+
+			if ( is_array( $value ) ) {
+				$string .= "<$tag>";
+				$string .= $this->array_to_xml_string( $value );
+				$string .= "</$tag>";
+			} elseif ( is_null( $value ) ) {
+				$string .= "<$tag />";
+			} else {
+				$string .= "<$tag>" . htmlspecialchars( $value ) . "</$tag>";
+			}
+		}
+
+		return $string;
+	}
+
+	/**
+	 * Render an associative array of XML attribute key/value pairs.
+	 *
+	 * @access public
+	 * @since 5.3.0
+	 *
+	 * @param array $array Key/value array of attributes.
+	 *
+	 * @return string The rendered attribute string.
+	 */
+	public static function array_to_xml_attr_string( $array ) {
+		$string = '';
+
+		foreach ( $array as $key => $value ) {
+			$key = preg_replace( '/[^a-zA-Z:_-]/', '_', $key );
+			$string .= ' ' . $key . '="' . esc_attr( $value ) . '"';
+		}
+
+		return $string;
+	}
+
+}
diff --git a/plugins/jetpack/modules/sitemaps/sitemap-buffer-image-fallback.php b/plugins/jetpack/modules/sitemaps/sitemap-buffer-image-fallback.php
new file mode 100644
index 00000000..1616574f
--- /dev/null
+++ b/plugins/jetpack/modules/sitemaps/sitemap-buffer-image-fallback.php
@@ -0,0 +1,56 @@
+<?php
+/**
+ * Sitemaps (per the protocol) are essentially lists of XML fragments;
+ * lists which are subject to size constraints. The Jetpack_Sitemap_Buffer_Image
+ * extends the Jetpack_Sitemap_Buffer class to represent the single image sitemap
+ * buffer.
+ *
+ * @since 5.3.0
+ * @package Jetpack
+ */
+
+/**
+ * A buffer for constructing sitemap image xml files for users that have no libxml support.
+ *
+ * @since 5.3.0
+ */
+class Jetpack_Sitemap_Buffer_Image extends Jetpack_Sitemap_Buffer_Fallback {
+
+	protected function get_root_element() {
+		if ( ! isset( $this->root ) ) {
+
+			/**
+			 * Filter the XML namespaces included in image sitemaps.
+			 *
+			 * @module sitemaps
+			 *
+			 * @since 4.8.0
+			 *
+			 * @param array $namespaces Associative array with namespaces and namespace URIs.
+			 */
+			$namespaces = apply_filters(
+				'jetpack_sitemap_image_ns',
+				array(
+					'xmlns:xsi'          => 'http://www.w3.org/2001/XMLSchema-instance',
+					'xsi:schemaLocation' => 'http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd',
+					'xmlns'              => 'http://www.sitemaps.org/schemas/sitemap/0.9',
+					'xmlns:image'        => 'http://www.google.com/schemas/sitemap-image/1.1',
+				)
+			);
+
+			$sitemap_xsl_url = $this->finder->construct_sitemap_url( 'sitemap.xsl' );
+			$jetpack_version = JETPACK__VERSION;
+
+			$this->root = array(
+				"<!-- generator='jetpack-{$jetpack_version}' -->" . PHP_EOL
+				. "<?xml-stylesheet type='text/xsl' href='{$sitemap_xsl_url}'?>" . PHP_EOL
+				. '<urlset ' . $this->array_to_xml_attr_string( $namespaces ) . '>' . PHP_EOL,
+				'</urlset>'
+			);
+
+			$this->byte_capacity -= strlen( join( '', $this->root ) );
+		}
+
+		return $this->root;
+	}
+}
diff --git a/plugins/jetpack/modules/sitemaps/sitemap-buffer-image.php b/plugins/jetpack/modules/sitemaps/sitemap-buffer-image.php
new file mode 100644
index 00000000..e452fcbf
--- /dev/null
+++ b/plugins/jetpack/modules/sitemaps/sitemap-buffer-image.php
@@ -0,0 +1,68 @@
+<?php
+/**
+ * Sitemaps (per the protocol) are essentially lists of XML fragments;
+ * lists which are subject to size constraints. The Jetpack_Sitemap_Buffer_Image
+ * extends the Jetpack_Sitemap_Buffer class to represent the single image sitemap
+ * buffer.
+ *
+ * @since 5.3.0
+ * @package Jetpack
+ */
+
+/**
+ * A buffer for constructing sitemap image xml files.
+ *
+ * @since 5.3.0
+ */
+class Jetpack_Sitemap_Buffer_Image extends Jetpack_Sitemap_Buffer {
+
+	public function __construct( $item_limit, $byte_limit, $time = '1970-01-01 00:00:00' ) {
+		parent::__construct( $item_limit, $byte_limit, $time );
+
+		$this->doc->appendChild(
+			$this->doc->createComment( "generator='jetpack-" . JETPACK__VERSION . "'" )
+		);
+
+		$this->doc->appendChild(
+			$this->doc->createProcessingInstruction(
+				'xml-stylesheet',
+				'type="text/xsl" href="' . $this->finder->construct_sitemap_url( 'image-sitemap.xsl' ) . '"'
+			)
+		);
+	}
+
+	protected function get_root_element() {
+		if ( ! isset( $this->root ) ) {
+
+			/**
+			 * Filter the XML namespaces included in image sitemaps.
+			 *
+			 * @module sitemaps
+			 *
+			 * @since 4.8.0
+			 *
+			 * @param array $namespaces Associative array with namespaces and namespace URIs.
+			 */
+			$namespaces = apply_filters(
+				'jetpack_sitemap_image_ns',
+				array(
+					'xmlns:xsi'          => 'http://www.w3.org/2001/XMLSchema-instance',
+					'xsi:schemaLocation' => 'http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd',
+					'xmlns'              => 'http://www.sitemaps.org/schemas/sitemap/0.9',
+					'xmlns:image'        => 'http://www.google.com/schemas/sitemap-image/1.1',
+				)
+			);
+
+			$this->root = $this->doc->createElement( 'urlset' );
+
+			foreach ( $namespaces as $name => $value ) {
+				$this->root->setAttribute( $name, $value );
+			}
+
+			$this->doc->appendChild( $this->root );
+			$this->byte_capacity -= strlen( $this->doc->saveXML( $this->root ) );
+		}
+
+		return $this->root;
+	}
+}
diff --git a/plugins/jetpack/modules/sitemaps/sitemap-buffer-master-fallback.php b/plugins/jetpack/modules/sitemaps/sitemap-buffer-master-fallback.php
new file mode 100644
index 00000000..af665547
--- /dev/null
+++ b/plugins/jetpack/modules/sitemaps/sitemap-buffer-master-fallback.php
@@ -0,0 +1,38 @@
+<?php
+/**
+ * Sitemaps (per the protocol) are essentially lists of XML fragments;
+ * lists which are subject to size constraints. The Jetpack_Sitemap_Buffer_Master
+ * extends the Jetpack_Sitemap_Buffer class to represent the master sitemap
+ * buffer.
+ *
+ * @since 5.3.0
+ * @package Jetpack
+ */
+
+/**
+ * A buffer for constructing master sitemap xml files for users without libxml support.
+ *
+ * @since 5.3.0
+ */
+class Jetpack_Sitemap_Buffer_Master extends Jetpack_Sitemap_Buffer_Fallback {
+
+	protected function get_root_element() {
+
+		if ( ! isset( $this->root ) ) {
+
+			$sitemap_index_xsl_url = $this->finder->construct_sitemap_url( 'sitemap-index.xsl' );
+			$jetpack_version = JETPACK__VERSION;
+
+			$this->root = array(
+				"<!-- generator='jetpack-{$jetpack_version}' -->" . PHP_EOL
+				. "<?xml-stylesheet type='text/xsl' href='{$sitemap_index_xsl_url}'?>" . PHP_EOL
+				. "<sitemapindex xmlns='http://www.sitemaps.org/schemas/sitemap/0.9'>" . PHP_EOL,
+				'</sitemapindex>'
+			);
+
+			$this->byte_capacity -= strlen( join( '', $this->root ) );
+		}
+
+		return $this->root;
+	}
+}
diff --git a/plugins/jetpack/modules/sitemaps/sitemap-buffer-master.php b/plugins/jetpack/modules/sitemaps/sitemap-buffer-master.php
new file mode 100644
index 00000000..fc6be602
--- /dev/null
+++ b/plugins/jetpack/modules/sitemaps/sitemap-buffer-master.php
@@ -0,0 +1,44 @@
+<?php
+/**
+ * Sitemaps (per the protocol) are essentially lists of XML fragments;
+ * lists which are subject to size constraints. The Jetpack_Sitemap_Buffer_Master
+ * extends the Jetpack_Sitemap_Buffer class to represent the master sitemap
+ * buffer.
+ *
+ * @since 5.3.0
+ * @package Jetpack
+ */
+
+/**
+ * A buffer for constructing master sitemap xml files.
+ *
+ * @since 5.3.0
+ */
+class Jetpack_Sitemap_Buffer_Master extends Jetpack_Sitemap_Buffer {
+
+	public function __construct( $item_limit, $byte_limit, $time = '1970-01-01 00:00:00' ) {
+		parent::__construct( $item_limit, $byte_limit, $time );
+
+		$this->doc->appendChild(
+			$this->doc->createComment( "generator='jetpack-" . JETPACK__VERSION . "'" )
+		);
+
+		$this->doc->appendChild(
+			$this->doc->createProcessingInstruction(
+				'xml-stylesheet',
+				'type="text/xsl" href="' . $this->finder->construct_sitemap_url( 'sitemap-index.xsl' ) . '"'
+			)
+		);
+	}
+
+	protected function get_root_element() {
+		if ( ! isset( $this->root ) ) {
+			$this->root = $this->doc->createElement( 'sitemapindex' );
+			$this->root->setAttribute( 'xmlns', 'http://www.sitemaps.org/schemas/sitemap/0.9' );
+			$this->doc->appendChild( $this->root );
+			$this->byte_capacity -= strlen( $this->doc->saveXML( $this->root ) );
+		}
+
+		return $this->root;
+	}
+}
diff --git a/plugins/jetpack/modules/sitemaps/sitemap-buffer-news-fallback.php b/plugins/jetpack/modules/sitemaps/sitemap-buffer-news-fallback.php
new file mode 100644
index 00000000..cca2c644
--- /dev/null
+++ b/plugins/jetpack/modules/sitemaps/sitemap-buffer-news-fallback.php
@@ -0,0 +1,56 @@
+<?php
+/**
+ * Sitemaps (per the protocol) are essentially lists of XML fragments;
+ * lists which are subject to size constraints. The Jetpack_Sitemap_Buffer_News
+ * extends the Jetpack_Sitemap_Buffer class to represent the single news sitemap
+ * buffer.
+ *
+ * @since 5.3.0
+ * @package Jetpack
+ */
+
+/**
+ * A buffer for constructing sitemap image xml files for users without libxml support.
+ *
+ * @since 5.3.0
+ */
+class Jetpack_Sitemap_Buffer_News extends Jetpack_Sitemap_Buffer_Fallback {
+
+	protected function get_root_element() {
+		if ( ! isset( $this->root ) ) {
+
+			/**
+			 * Filter the attribute value pairs used for namespace and namespace URI mappings.
+			 *
+			 * @module sitemaps
+			 *
+			 * @since 4.8.0
+			 *
+			 * @param array $namespaces Associative array with namespaces and namespace URIs.
+			 */
+			$namespaces = apply_filters(
+				'jetpack_sitemap_news_ns',
+				array(
+					'xmlns:xsi'          => 'http://www.w3.org/2001/XMLSchema-instance',
+					'xsi:schemaLocation' => 'http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd',
+					'xmlns'              => 'http://www.sitemaps.org/schemas/sitemap/0.9',
+					'xmlns:news'         => 'http://www.google.com/schemas/sitemap-news/0.9',
+				)
+			);
+
+			$jetpack_version = JETPACK__VERSION;
+			$news_sitemap_xsl_url = $this->finder->construct_sitemap_url( 'news-sitemap.xsl' );
+
+			$this->root = array(
+				"<!-- generator='jetpack-{$jetpack_version}' -->" . PHP_EOL
+				. "<?xml-stylesheet type='text/xsl' href='{$news_sitemap_xsl_url}'?>" . PHP_EOL
+				. '<urlset ' . $this->array_to_xml_attr_string( $namespaces ) . '>',
+				'</urlset>'
+			);
+
+			$this->byte_capacity -= strlen( join( '', $this->root ) );
+		}
+
+		return $this->root;
+	}
+}
diff --git a/plugins/jetpack/modules/sitemaps/sitemap-buffer-news.php b/plugins/jetpack/modules/sitemaps/sitemap-buffer-news.php
new file mode 100644
index 00000000..0e5b0327
--- /dev/null
+++ b/plugins/jetpack/modules/sitemaps/sitemap-buffer-news.php
@@ -0,0 +1,68 @@
+<?php
+/**
+ * Sitemaps (per the protocol) are essentially lists of XML fragments;
+ * lists which are subject to size constraints. The Jetpack_Sitemap_Buffer_News
+ * extends the Jetpack_Sitemap_Buffer class to represent the single news sitemap
+ * buffer.
+ *
+ * @since 5.3.0
+ * @package Jetpack
+ */
+
+/**
+ * A buffer for constructing sitemap image xml files.
+ *
+ * @since 5.3.0
+ */
+class Jetpack_Sitemap_Buffer_News extends Jetpack_Sitemap_Buffer {
+
+	public function __construct( $item_limit, $byte_limit, $time = '1970-01-01 00:00:00' ) {
+		parent::__construct( $item_limit, $byte_limit, $time );
+
+		$this->doc->appendChild(
+			$this->doc->createComment( "generator='jetpack-" . JETPACK__VERSION . "'" )
+		);
+
+		$this->doc->appendChild(
+			$this->doc->createProcessingInstruction(
+				'xml-stylesheet',
+				'type="text/xsl" href="' . $this->finder->construct_sitemap_url( 'news-sitemap.xsl' ) . '"'
+			)
+		);
+	}
+
+	protected function get_root_element() {
+		if ( ! isset( $this->root ) ) {
+
+			/**
+			 * Filter the attribute value pairs used for namespace and namespace URI mappings.
+			 *
+			 * @module sitemaps
+			 *
+			 * @since 4.8.0
+			 *
+			 * @param array $namespaces Associative array with namespaces and namespace URIs.
+			 */
+			$namespaces = apply_filters(
+				'jetpack_sitemap_news_ns',
+				array(
+					'xmlns:xsi'          => 'http://www.w3.org/2001/XMLSchema-instance',
+					'xsi:schemaLocation' => 'http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd',
+					'xmlns'              => 'http://www.sitemaps.org/schemas/sitemap/0.9',
+					'xmlns:news'         => 'http://www.google.com/schemas/sitemap-news/0.9',
+				)
+			);
+
+			$this->root = $this->doc->createElement( 'urlset' );
+
+			foreach ( $namespaces as $name => $value ) {
+				$this->root->setAttribute( $name, $value );
+			}
+
+			$this->doc->appendChild( $this->root );
+			$this->byte_capacity -= strlen( $this->doc->saveXML( $this->root ) );
+		}
+
+		return $this->root;
+	}
+}
diff --git a/plugins/jetpack/modules/sitemaps/sitemap-buffer-page-fallback.php b/plugins/jetpack/modules/sitemaps/sitemap-buffer-page-fallback.php
new file mode 100644
index 00000000..e64f31bc
--- /dev/null
+++ b/plugins/jetpack/modules/sitemaps/sitemap-buffer-page-fallback.php
@@ -0,0 +1,55 @@
+<?php
+/**
+ * Sitemaps (per the protocol) are essentially lists of XML fragments;
+ * lists which are subject to size constraints. The Jetpack_Sitemap_Buffer_Page
+ * extends the Jetpack_Sitemap_Buffer class to represent the single page sitemap
+ * buffer.
+ *
+ * @since 5.3.0
+ * @package Jetpack
+ */
+
+/**
+ * A buffer for constructing sitemap page xml files for users with no libxml support.
+ *
+ * @since 5.3.0
+ */
+class Jetpack_Sitemap_Buffer_Page extends Jetpack_Sitemap_Buffer_Fallback {
+
+	protected function get_root_element() {
+		if ( ! isset( $this->root ) ) {
+
+			/**
+			 * Filter the attribute value pairs used for namespace and namespace URI mappings.
+			 *
+			 * @module sitemaps
+			 *
+			 * @since 3.9.0
+			 *
+			 * @param array $namespaces Associative array with namespaces and namespace URIs.
+			 */
+			$namespaces = apply_filters(
+				'jetpack_sitemap_ns',
+				array(
+					'xmlns:xsi'          => 'http://www.w3.org/2001/XMLSchema-instance',
+					'xsi:schemaLocation' => 'http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd',
+					'xmlns'              => 'http://www.sitemaps.org/schemas/sitemap/0.9',
+				)
+			);
+
+			$jetpack_version = JETPACK__VERSION;
+			$sitemap_xsl_url = $this->finder->construct_sitemap_url( 'sitemap.xsl' );
+
+			$this->root = array(
+				"<!-- generator='jetpack-{$jetpack_version}' -->" . PHP_EOL
+				. "<?xml-stylesheet type='text/xsl' href='{$sitemap_xsl_url}'?>" . PHP_EOL
+				. '<urlset ' . $this->array_to_xml_attr_string( $namespaces ) . '>',
+				'</urlset>'
+			);
+
+			$this->byte_capacity -= strlen( join( '', $this->root ) );
+		}
+
+		return $this->root;
+	}
+}
diff --git a/plugins/jetpack/modules/sitemaps/sitemap-buffer-page.php b/plugins/jetpack/modules/sitemaps/sitemap-buffer-page.php
new file mode 100644
index 00000000..d6885900
--- /dev/null
+++ b/plugins/jetpack/modules/sitemaps/sitemap-buffer-page.php
@@ -0,0 +1,67 @@
+<?php
+/**
+ * Sitemaps (per the protocol) are essentially lists of XML fragments;
+ * lists which are subject to size constraints. The Jetpack_Sitemap_Buffer_Page
+ * extends the Jetpack_Sitemap_Buffer class to represent the single page sitemap
+ * buffer.
+ *
+ * @since 5.3.0
+ * @package Jetpack
+ */
+
+/**
+ * A buffer for constructing sitemap page xml files.
+ *
+ * @since 5.3.0
+ */
+class Jetpack_Sitemap_Buffer_Page extends Jetpack_Sitemap_Buffer {
+
+	public function __construct( $item_limit, $byte_limit, $time = '1970-01-01 00:00:00' ) {
+		parent::__construct( $item_limit, $byte_limit, $time );
+
+		$this->doc->appendChild(
+			$this->doc->createComment( "generator='jetpack-" . JETPACK__VERSION . "'" )
+		);
+
+		$this->doc->appendChild(
+			$this->doc->createProcessingInstruction(
+				'xml-stylesheet',
+				'type="text/xsl" href="' . $this->finder->construct_sitemap_url( 'sitemap.xsl' ) . '"'
+			)
+		);
+	}
+
+	protected function get_root_element() {
+		if ( ! isset( $this->root ) ) {
+
+			/**
+			 * Filter the attribute value pairs used for namespace and namespace URI mappings.
+			 *
+			 * @module sitemaps
+			 *
+			 * @since 3.9.0
+			 *
+			 * @param array $namespaces Associative array with namespaces and namespace URIs.
+			 */
+			$namespaces = apply_filters(
+				'jetpack_sitemap_ns',
+				array(
+					'xmlns:xsi'          => 'http://www.w3.org/2001/XMLSchema-instance',
+					'xsi:schemaLocation' => 'http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd',
+					'xmlns'              => 'http://www.sitemaps.org/schemas/sitemap/0.9',
+				)
+			);
+
+			$this->root = $this->doc->createElement( 'urlset' );
+
+			foreach ( $namespaces as $name => $value ) {
+				$this->root->setAttribute( $name, $value );
+			}
+
+			$this->doc->appendChild( $this->root );
+			$this->byte_capacity -= strlen( $this->doc->saveXML( $this->root ) );
+		}
+
+		return $this->root;
+	}
+}
diff --git a/plugins/jetpack/modules/sitemaps/sitemap-buffer-video-fallback.php b/plugins/jetpack/modules/sitemaps/sitemap-buffer-video-fallback.php
new file mode 100644
index 00000000..d211877d
--- /dev/null
+++ b/plugins/jetpack/modules/sitemaps/sitemap-buffer-video-fallback.php
@@ -0,0 +1,56 @@
+<?php
+/**
+ * Sitemaps (per the protocol) are essentially lists of XML fragments;
+ * lists which are subject to size constraints. The Jetpack_Sitemap_Buffer_Video
+ * extends the Jetpack_Sitemap_Buffer class to represent the single video sitemap
+ * buffer.
+ *
+ * @since 5.3.0
+ * @package Jetpack
+ */
+
+/**
+ * A buffer for constructing sitemap video xml files for users without libxml support.
+ *
+ * @since 5.3.0
+ */
+class Jetpack_Sitemap_Buffer_Video extends Jetpack_Sitemap_Buffer_Fallback {
+
+	protected function get_root_element() {
+		if ( ! isset( $this->root ) ) {
+
+			/**
+			 * Filter the XML namespaces included in video sitemaps.
+			 *
+			 * @module sitemaps
+			 *
+			 * @since 4.8.0
+			 *
+			 * @param array $namespaces Associative array with namespaces and namespace URIs.
+			 */
+			$namespaces = apply_filters(
+				'jetpack_sitemap_video_ns',
+				array(
+					'xmlns:xsi'          => 'http://www.w3.org/2001/XMLSchema-instance',
+					'xsi:schemaLocation' => 'http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd',
+					'xmlns'              => 'http://www.sitemaps.org/schemas/sitemap/0.9',
+					'xmlns:video'        => 'http://www.google.com/schemas/sitemap-video/1.1',
+				)
+			);
+
+			$video_sitemap_xsl_url = $this->finder->construct_sitemap_url( 'video-sitemap.xsl' );
+			$jetpack_version = JETPACK__VERSION;
+
+			$this->root = array(
+				"<!-- generator='jetpack-{$jetpack_version}' -->" . PHP_EOL
+				. "<?xml-stylesheet type='text/xsl' href='{$video_sitemap_xsl_url}'?>" . PHP_EOL
+				. '<urlset ' . $this->array_to_xml_attr_string( $namespaces ) . '>',
+				'</urlset>'
+			);
+
+			$this->byte_capacity -= strlen( join( '', $this->root ) );
+		}
+
+		return $this->root;
+	}
+}
diff --git a/plugins/jetpack/modules/sitemaps/sitemap-buffer-video.php b/plugins/jetpack/modules/sitemaps/sitemap-buffer-video.php
new file mode 100644
index 00000000..c6faff36
--- /dev/null
+++ b/plugins/jetpack/modules/sitemaps/sitemap-buffer-video.php
@@ -0,0 +1,68 @@
+<?php
+/**
+ * Sitemaps (per the protocol) are essentially lists of XML fragments;
+ * lists which are subject to size constraints. The Jetpack_Sitemap_Buffer_Video
+ * extends the Jetpack_Sitemap_Buffer class to represent the single video sitemap
+ * buffer.
+ *
+ * @since 5.3.0
+ * @package Jetpack
+ */
+
+/**
+ * A buffer for constructing sitemap video xml files.
+ *
+ * @since 5.3.0
+ */
+class Jetpack_Sitemap_Buffer_Video extends Jetpack_Sitemap_Buffer {
+
+	public function __construct( $item_limit, $byte_limit, $time = '1970-01-01 00:00:00' ) {
+		parent::__construct( $item_limit, $byte_limit, $time );
+
+		$this->doc->appendChild(
+			$this->doc->createComment( "generator='jetpack-" . JETPACK__VERSION . "'" )
+		);
+
+		$this->doc->appendChild(
+			$this->doc->createProcessingInstruction(
+				'xml-stylesheet',
+				'type="text/xsl" href="' . $this->finder->construct_sitemap_url( 'video-sitemap.xsl' ) . '"'
+			)
+		);
+	}
+
+	protected function get_root_element() {
+		if ( ! isset( $this->root ) ) {
+
+			/**
+			 * Filter the XML namespaces included in video sitemaps.
+			 *
+			 * @module sitemaps
+			 *
+			 * @since 4.8.0
+			 *
+			 * @param array $namespaces Associative array with namespaces and namespace URIs.
+			 */
+			$namespaces = apply_filters(
+				'jetpack_sitemap_video_ns',
+				array(
+					'xmlns:xsi'          => 'http://www.w3.org/2001/XMLSchema-instance',
+					'xsi:schemaLocation' => 'http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd',
+					'xmlns'              => 'http://www.sitemaps.org/schemas/sitemap/0.9',
+					'xmlns:video'        => 'http://www.google.com/schemas/sitemap-video/1.1',
+				)
+			);
+
+			$this->root = $this->doc->createElement( 'urlset' );
+
+			foreach ( $namespaces as $name => $value ) {
+				$this->root->setAttribute( $name, $value );
+			}
+
+			$this->doc->appendChild( $this->root );
+			$this->byte_capacity -= strlen( $this->doc->saveXML( $this->root ) );
+		}
+
+		return $this->root;
+	}
+}
diff --git a/plugins/jetpack/modules/sitemaps/sitemap-buffer.php b/plugins/jetpack/modules/sitemaps/sitemap-buffer.php
index f1a8d9b1..0853a49a 100644
--- a/plugins/jetpack/modules/sitemaps/sitemap-buffer.php
+++ b/plugins/jetpack/modules/sitemaps/sitemap-buffer.php
@@ -22,70 +22,80 @@
  *
  * @since 4.8.0
  */
-class Jetpack_Sitemap_Buffer {
+abstract class Jetpack_Sitemap_Buffer {
 
 	/**
 	 * Largest number of items the buffer can hold.
 	 *
-	 * @access private
+	 * @access protected
 	 * @since 4.8.0
 	 * @var int $item_capacity The item capacity.
 	 */
-	private $item_capacity;
+	protected $item_capacity;
 
 	/**
 	 * Largest number of bytes the buffer can hold.
 	 *
-	 * @access private
+	 * @access protected
 	 * @since 4.8.0
 	 * @var int $byte_capacity The byte capacity.
 	 */
-	private $byte_capacity;
+	protected $byte_capacity;
 
 	/**
-	 * Footer text of the buffer; stored here so it can be appended when the buffer is full.
+	 * Flag which detects when the buffer is full.
 	 *
-	 * @access private
+	 * @access protected
 	 * @since 4.8.0
-	 * @var string $footer_text The footer text.
+	 * @var bool $is_full_flag The flag value. This flag is set to false on construction and only flipped to true if we've tried to add something and failed.
 	 */
-	private $footer_text;
+	protected $is_full_flag;
 
 	/**
-	 * The buffer contents.
+	 * Flag which detects when the buffer is empty.
 	 *
-	 * @access private
+	 * @access protected
 	 * @since 4.8.0
-	 * @var string The buffer contents.
+	 * @var bool $is_empty_flag The flag value. This flag is set to true on construction and only flipped to false if we've tried to add something and succeeded.
 	 */
-	private $buffer;
+	protected $is_empty_flag;
 
 	/**
-	 * Flag which detects when the buffer is full.
+	 * The most recent timestamp seen by the buffer.
 	 *
-	 * @access private
+	 * @access protected
 	 * @since 4.8.0
-	 * @var bool $is_full_flag The flag value. This flag is set to false on construction and only flipped to true if we've tried to add something and failed.
+	 * @var string $timestamp Must be in 'YYYY-MM-DD hh:mm:ss' format.
 	 */
-	private $is_full_flag;
+	protected $timestamp;
 
 	/**
-	 * Flag which detects when the buffer is empty.
+	 * The DOM document object that is currently being used to construct the XML doc.
 	 *
-	 * @access private
-	 * @since 4.8.0
-	 * @var bool $is_empty_flag The flag value. This flag is set to true on construction and only flipped to false if we've tried to add something and succeeded.
+	 * @access protected
+	 * @since 5.3.0
+	 * @var DOMDocument $doc
 	 */
-	private $is_empty_flag;
+	protected $doc = null;
 
 	/**
-	 * The most recent timestamp seen by the buffer.
+	 * The root DOM element object that holds everything inside. Do not use directly, call
+	 * the get_root_element getter method instead.
 	 *
-	 * @access private
-	 * @since 4.8.0
-	 * @var string $timestamp Must be in 'YYYY-MM-DD hh:mm:ss' format.
+	 * @access protected
+	 * @since 5.3.0
+	 * @var DOMElement $doc
+	 */
+	protected $root = null;
+
+	/**
+	 * Helper class to construct sitemap paths.
+	 *
+	 * @since 5.3.0
+	 * @protected
+	 * @var Jetpack_Sitemap_Finder
 	 */
-	private $timestamp;
+	protected $finder;
 
 	/**
 	 * Construct a new Jetpack_Sitemap_Buffer.
@@ -94,32 +104,29 @@ class Jetpack_Sitemap_Buffer {
 	 *
 	 * @param int    $item_limit The maximum size of the buffer in items.
 	 * @param int    $byte_limit The maximum size of the buffer in bytes.
-	 * @param string $header The string to prepend to the entire buffer.
-	 * @param string $footer The string to append to the entire buffer.
 	 * @param string $time The initial datetime of the buffer. Must be in 'YYYY-MM-DD hh:mm:ss' format.
 	 */
-	public function __construct(
-		$item_limit,
-		$byte_limit,
-		$header = '',
-		$footer = '',
-		$time
-	) {
-		$this->item_capacity = max( 1, intval( $item_limit ) );
-
-		mbstring_binary_safe_encoding(); // So we can safely use strlen().
-		$this->byte_capacity = max( 1, intval( $byte_limit ) ) - strlen( $header ) - strlen( $footer );
-		reset_mbstring_encoding();
-
-		$this->footer_text = $footer;
-		$this->buffer = $header;
+	public function __construct( $item_limit, $byte_limit, $time ) {
 		$this->is_full_flag = false;
-		$this->is_empty_flag = true;
 		$this->timestamp = $time;
-		return;
+
+		$this->finder = new Jetpack_Sitemap_Finder();
+		$this->doc = new DOMDocument( '1.0', 'UTF-8' );
+
+		$this->item_capacity = max( 1, intval( $item_limit ) );
+		$this->byte_capacity = max( 1, intval( $byte_limit ) ) - strlen( $this->doc->saveXML() );
 	}
 
 	/**
+	 * Returns a DOM element that contains all sitemap elements.
+	 *
+	 * @access protected
+	 * @since 5.3.0
+	 * @return DOMElement $root
+	 */
+	abstract protected function get_root_element();
+
+	/**
 	 * Append an item to the buffer, if there is room for it,
 	 * and set is_empty_flag to false. If there is no room,
 	 * we set is_full_flag to true. If $item is null,
@@ -132,24 +139,45 @@ class Jetpack_Sitemap_Buffer {
 	 * @return bool True if the append succeeded, False if not.
 	 */
 	public function try_to_add_item( $item ) {
-		if ( is_null( $item ) ) {
+		_deprecated_function(
+			'Jetpack_Sitemap_Buffer::try_to_add_item',
+			'5.3.0',
+			'Jetpack_Sitemap_Buffer::append'
+		);
+		$this->append( $item );
+	}
+
+	/**
+	 * Append an item to the buffer, if there is room for it,
+	 * and set is_empty_flag to false. If there is no room,
+	 * we set is_full_flag to true. If $item is null,
+	 * don't do anything and report success.
+	 *
+	 * @since 5.3.0
+	 *
+	 * @param array $array The item to be added.
+	 *
+	 * @return bool True if the append succeeded, False if not.
+	 */
+	public function append( $array ) {
+		if ( is_null( $array ) ) {
 			return true;
+		}
+
+		if ( $this->is_full_flag ) {
+			return false;
+		}
+
+		if ( 0 >= $this->item_capacity || 0 >= $this->byte_capacity ) {
+			$this->is_full_flag = true;
+			return false;
 		} else {
+			$this->item_capacity -= 1;
+			$added_element = $this->array_to_xml_string( $array, $this->get_root_element(), $this->doc );
 
-			mbstring_binary_safe_encoding(); // So we can safely use strlen().
-			$item_size = strlen( $item ); // Size in bytes.
-			reset_mbstring_encoding();
+			$this->byte_capacity -= strlen( $this->doc->saveXML( $added_element ) );
 
-			if ( 0 >= $this->item_capacity || 0 > $this->byte_capacity - $item_size ) {
-				$this->is_full_flag = true;
-				return false;
-			} else {
-				$this->is_empty_flag = false;
-				$this->item_capacity -= 1;
-				$this->byte_capacity -= $item_size;
-				$this->buffer .= $item;
-				return true;
-			}
+			return true;
 		}
 	}
 
@@ -161,7 +189,21 @@ class Jetpack_Sitemap_Buffer {
 	 * @return string The contents of the buffer (with the footer included).
 	 */
 	public function contents() {
-		return $this->buffer . $this->footer_text;
+		if( $this->is_empty() ) {
+			// The sitemap should have at least the root element added to the DOM
+			$this->get_root_element();
+		}
+		return $this->doc->saveXML();
+	}
+
+	/**
+	 * Retrieve the document object.
+	 *
+	 * @since 5.3.0
+	 * @return DOMDocument $doc
+	 */
+	public function get_document() {
+		return $this->doc;
 	}
 
 	/**
@@ -183,7 +225,10 @@ class Jetpack_Sitemap_Buffer {
 	 * @return bool True if the buffer is empty, false otherwise.
 	 */
 	public function is_empty() {
-		return $this->is_empty_flag;
+		return (
+			! isset( $this->root )
+			|| ! $this->root->hasChildNodes()
+		);
 	}
 
 	/**
@@ -195,7 +240,6 @@ class Jetpack_Sitemap_Buffer {
 	 */
 	public function view_time( $new_time ) {
 		$this->timestamp = max( $this->timestamp, $new_time );
-		return;
 	}
 
 	/**
@@ -231,56 +275,52 @@ class Jetpack_Sitemap_Buffer {
 	 *   ),                                  |</html>
 	 * )
 	 *
-	 * @access public
+	 * @access protected
 	 * @since 3.9.0
 	 * @since 4.8.0 Rename, add $depth parameter, and change return type.
+	 * @since 5.3.0 Refactor, remove $depth parameter, add $parent and $root, make access protected.
 	 *
 	 * @param array  $array A recursive associative array of tag/child relationships.
-	 * @param string $depth String to prepend to each line. For internal use only.
+	 * @param DOMElement $parent (optional) an element to which new children should be added.
+	 * @param DOMDocument $root (optional) the parent document.
 	 *
-	 * @return string The rendered XML string.
+	 * @return string|DOMDocument The rendered XML string or an object if root element is specified.
 	 */
-	public static function array_to_xml_string( $array, $depth = '' ) {
-		$string = '';
-
-		foreach ( $array as $key => $value ) {
+	protected function array_to_xml_string( $array, $parent = null, $root = null ) {
+		$return_string = false;
 
-			// Only allow a-z, A-Z, colon, underscore, and hyphen.
-			$tag = preg_replace( '/[^a-zA-Z:_-]/', '_', $key );
-
-			if ( is_array( $value ) ) {
-				$string .= $depth . "<$tag>\n";
-				$string .= self::array_to_xml_string( $value, $depth . '  ' );
-				$string .= $depth . "</$tag>\n";
-			} elseif ( is_null( $value ) ) {
-				$string .= $depth . "<$tag />\n";
-			} else {
-				$string .= $depth . "<$tag>" . ent2ncr( $value ) . "</$tag>\n";
-			}
+		if ( null === $parent ) {
+			$return_string = true;
+			$parent = $root = new DOMDocument();
 		}
 
-		return $string;
-	}
+		if ( is_array( $array ) ) {
 
-	/**
-	 * Render an associative array of XML attribute key/value pairs.
-	 *
-	 * @access public
-	 * @since 4.8.0
-	 *
-	 * @param array $array Key/value array of attributes.
-	 *
-	 * @return string The rendered attribute string.
-	 */
-	public static function array_to_xml_attr_string( $array ) {
-		$string = '';
+			foreach ( $array as $key => $value ) {
+				$element = $root->createElement( $key );
+				$parent->appendChild( $element );
 
-		foreach ( $array as $key => $value ) {
-			$key = preg_replace( '/[^a-zA-Z:_-]/', '_', $key );
-			$string .= ' ' . $key . '="' . esc_attr( $value ) . '"';
+				if ( is_array( $value ) ) {
+					foreach ( $value as $child_key => $child_value ) {
+						$child = $root->createElement( $child_key );
+						$element->appendChild( $child );
+						$child->appendChild( self::array_to_xml_string( $child_value, $child, $root ) );
+					}
+				} else {
+					$element->appendChild(
+						$root->createTextNode( $value )
+					);
+				}
+			}
+		} else {
+			$element = $root->createTextNode( $array );
+			$parent->appendChild( $element );
 		}
 
-		return $string;
+		if ( $return_string ) {
+			return $root->saveHTML();
+		} else {
+			return $element;
+		}
 	}
-
 }
diff --git a/plugins/jetpack/modules/sitemaps/sitemap-builder.php b/plugins/jetpack/modules/sitemaps/sitemap-builder.php
index cfd7b9a1..9cf91c24 100644
--- a/plugins/jetpack/modules/sitemaps/sitemap-builder.php
+++ b/plugins/jetpack/modules/sitemaps/sitemap-builder.php
@@ -9,6 +9,22 @@
 
 require_once dirname( __FILE__ ) . '/sitemap-constants.php';
 require_once dirname( __FILE__ ) . '/sitemap-buffer.php';
+
+if ( ! class_exists( 'DOMDocument' ) ) {
+	require_once dirname( __FILE__ ) . '/sitemap-buffer-fallback.php';
+	require_once dirname( __FILE__ ) . '/sitemap-buffer-image-fallback.php';
+	require_once dirname( __FILE__ ) . '/sitemap-buffer-master-fallback.php';
+	require_once dirname( __FILE__ ) . '/sitemap-buffer-news-fallback.php';
+	require_once dirname( __FILE__ ) . '/sitemap-buffer-page-fallback.php';
+	require_once dirname( __FILE__ ) . '/sitemap-buffer-video-fallback.php';
+} else {
+	require_once dirname( __FILE__ ) . '/sitemap-buffer-image.php';
+	require_once dirname( __FILE__ ) . '/sitemap-buffer-master.php';
+	require_once dirname( __FILE__ ) . '/sitemap-buffer-news.php';
+	require_once dirname( __FILE__ ) . '/sitemap-buffer-page.php';
+	require_once dirname( __FILE__ ) . '/sitemap-buffer-video.php';
+}
+
 require_once dirname( __FILE__ ) . '/sitemap-librarian.php';
 require_once dirname( __FILE__ ) . '/sitemap-finder.php';
 require_once dirname( __FILE__ ) . '/sitemap-state.php';
@@ -87,8 +103,6 @@ class Jetpack_Sitemap_Builder {
 				array( 'post', 'page' )
 			)
 		);
-
-		return;
 	}
 
 	/**
@@ -101,6 +115,17 @@ class Jetpack_Sitemap_Builder {
 	public function update_sitemap() {
 		if ( $this->logger ) {
 			$this->logger->report( '-- Updating...' );
+			if ( ! class_exists( 'DOMDocument' ) ) {
+				$this->logger->report(
+					__(
+						'-- WARNING: Jetpack can not load necessary XML manipulation libraries. '
+						. 'This can happen if XML support in PHP is not enabled on your server. '
+						. 'XML support is highly recommended for WordPress and Jetpack, please enable '
+						. 'it or contact your hosting provider about it.',
+						'jetpack'
+					)
+				);
+			}
 		}
 
 		for ( $i = 1; $i <= JP_SITEMAP_UPDATE_SIZE; $i++ ) {
@@ -201,12 +226,10 @@ class Jetpack_Sitemap_Builder {
 					JP_PAGE_SITEMAP_TYPE
 				);
 				die();
-		}
+		} // End switch().
 
 		// Unlock the state.
 		Jetpack_Sitemap_State::unlock();
-
-		return;
 	}
 
 	/**
@@ -280,8 +303,6 @@ class Jetpack_Sitemap_Builder {
 		$this->librarian->delete_numbered_sitemap_rows_after(
 			$state['number'] + 1, $sitemap_type
 		);
-
-		return;
 	}
 
 	/**
@@ -387,29 +408,13 @@ class Jetpack_Sitemap_Builder {
 	 * @since 4.8.0
 	 */
 	private function build_master_sitemap( $max ) {
-		$sitemap_index_xsl_url = $this->finder->construct_sitemap_url( 'sitemap-index.xsl' );
-		$jetpack_version = JETPACK__VERSION;
-
 		if ( $this->logger ) {
 			$this->logger->report( '-- Building Master Sitemap.' );
 		}
 
-		$buffer = new Jetpack_Sitemap_Buffer(
+		$buffer = new Jetpack_Sitemap_Buffer_Master(
 			JP_SITEMAP_MAX_ITEMS,
-			JP_SITEMAP_MAX_BYTES,
-			<<<HEADER
-<?xml version='1.0' encoding='UTF-8'?>
-<!-- generator='jetpack-{$jetpack_version}' -->
-<?xml-stylesheet type='text/xsl' href='{$sitemap_index_xsl_url}'?>
-<sitemapindex xmlns='http://www.sitemaps.org/schemas/sitemap/0.9'>
-HEADER
-			,
-			<<<FOOTER
-</sitemapindex>\n
-FOOTER
-			,
-			/* epoch */
-			'1970-01-01 00:00:00'
+			JP_SITEMAP_MAX_BYTES
 		);
 
 		if ( 0 < $max[ JP_PAGE_SITEMAP_TYPE ]['number'] ) {
@@ -424,14 +429,14 @@ FOOTER
 				$page['last_modified'] = jp_sitemap_datetime( $max[ JP_PAGE_SITEMAP_INDEX_TYPE ]['lastmod'] );
 			}
 
-			$buffer->try_to_add_item( Jetpack_Sitemap_Buffer::array_to_xml_string(
+			$buffer->append(
 				array(
 					'sitemap' => array(
 						'loc'     => $this->finder->construct_sitemap_url( $page['filename'] ),
 						'lastmod' => $page['last_modified'],
 					),
 				)
-			) );
+			);
 		}
 
 		if ( 0 < $max[ JP_IMAGE_SITEMAP_TYPE ]['number'] ) {
@@ -446,14 +451,14 @@ FOOTER
 				$image['last_modified'] = jp_sitemap_datetime( $max[ JP_IMAGE_SITEMAP_INDEX_TYPE ]['lastmod'] );
 			}
 
-			$buffer->try_to_add_item( Jetpack_Sitemap_Buffer::array_to_xml_string(
+			$buffer->append(
 				array(
 					'sitemap' => array(
 						'loc'     => $this->finder->construct_sitemap_url( $image['filename'] ),
 						'lastmod' => $image['last_modified'],
 					),
 				)
-			) );
+			);
 		}
 
 		if ( 0 < $max[ JP_VIDEO_SITEMAP_TYPE ]['number'] ) {
@@ -468,14 +473,14 @@ FOOTER
 				$video['last_modified'] = $max[ JP_VIDEO_SITEMAP_INDEX_TYPE ]['lastmod'];
 			}
 
-			$buffer->try_to_add_item( Jetpack_Sitemap_Buffer::array_to_xml_string(
+			$buffer->append(
 				array(
 					'sitemap' => array(
 						'loc'     => $this->finder->construct_sitemap_url( $video['filename'] ),
 						'lastmod' => $video['last_modified'],
 					),
 				)
-			) );
+			);
 		}
 
 		$this->librarian->store_sitemap_data(
@@ -484,8 +489,6 @@ FOOTER
 			$buffer->contents(),
 			''
 		);
-
-		return;
 	}
 
 	/**
@@ -514,46 +517,9 @@ FOOTER
 			$this->logger->report( "-- Building $debug_name" );
 		}
 
-		$sitemap_xsl_url = $this->finder->construct_sitemap_url( 'sitemap.xsl' );
-
-		$jetpack_version = JETPACK__VERSION;
-
-		$namespaces = Jetpack_Sitemap_Buffer::array_to_xml_attr_string(
-			/**
-			 * Filter the attribute value pairs used for namespace and namespace URI mappings.
-			 *
-			 * @module sitemaps
-			 *
-			 * @since 3.9.0
-			 *
-			 * @param array $namespaces Associative array with namespaces and namespace URIs.
-			 */
-			apply_filters(
-				'jetpack_sitemap_ns',
-				array(
-					'xmlns:xsi'          => 'http://www.w3.org/2001/XMLSchema-instance',
-					'xsi:schemaLocation' => 'http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd',
-					'xmlns'              => 'http://www.sitemaps.org/schemas/sitemap/0.9',
-				)
-			)
-		);
-
-		$buffer = new Jetpack_Sitemap_Buffer(
+		$buffer = new Jetpack_Sitemap_Buffer_Page(
 			JP_SITEMAP_MAX_ITEMS,
-			JP_SITEMAP_MAX_BYTES,
-			<<<HEADER
-<?xml version='1.0' encoding='UTF-8'?>
-<!-- generator='jetpack-{$jetpack_version}' -->
-<?xml-stylesheet type='text/xsl' href='{$sitemap_xsl_url}'?>
-<urlset{$namespaces}>\n
-HEADER
-			,
-			<<<FOOTER
-</urlset>\n
-FOOTER
-			,
-			/* epoch */
-			'1970-01-01 00:00:00'
+			JP_SITEMAP_MAX_BYTES
 		);
 
 		// Add entry for the main page (only if we're at the first one).
@@ -576,7 +542,7 @@ FOOTER
 			 */
 			$item_array = apply_filters( 'jetpack_sitemap_url_home', $item_array );
 
-			$buffer->try_to_add_item( Jetpack_Sitemap_Buffer::array_to_xml_string( $item_array ) );
+			$buffer->append( $item_array );
 		}
 
 		// Add as many items to the buffer as possible.
@@ -593,7 +559,7 @@ FOOTER
 			foreach ( $posts as $post ) {
 				$current_item = $this->post_to_sitemap_item( $post );
 
-				if ( true === $buffer->try_to_add_item( $current_item['xml'] ) ) {
+				if ( true === $buffer->append( $current_item['xml'] ) ) {
 					$last_post_id = $post->ID;
 					$buffer->view_time( $current_item['last_modified'] );
 				} else {
@@ -613,13 +579,14 @@ FOOTER
 		 * @module sitemaps
 		 *
 		 * @since 3.9.0
+		 * @since 5.3.0 returns an element of DOMDocument type instead of SimpleXMLElement
 		 *
-		 * @param SimpleXMLElement $tree Data tree for sitemap.
+		 * @param DOMDocument      $doc Data tree for sitemap.
 		 * @param string           $last_modified Date of last modification.
 		 */
 		$tree = apply_filters(
 			'jetpack_print_sitemap',
-			simplexml_load_string( $buffer->contents() ),
+			$buffer->get_document(),
 			$buffer->last_modified()
 		);
 
@@ -627,7 +594,7 @@ FOOTER
 		$this->librarian->store_sitemap_data(
 			$number,
 			JP_PAGE_SITEMAP_TYPE,
-			$tree->asXML(),
+			$buffer->contents(),
 			$buffer->last_modified()
 		);
 
@@ -668,47 +635,9 @@ FOOTER
 			$this->logger->report( "-- Building $debug_name" );
 		}
 
-		$image_sitemap_xsl_url = $this->finder->construct_sitemap_url( 'image-sitemap.xsl' );
-
-		$jetpack_version = JETPACK__VERSION;
-
-		$namespaces = Jetpack_Sitemap_Buffer::array_to_xml_attr_string(
-			/**
-			 * Filter the XML namespaces included in image sitemaps.
-			 *
-			 * @module sitemaps
-			 *
-			 * @since 4.8.0
-			 *
-			 * @param array $namespaces Associative array with namespaces and namespace URIs.
-			 */
-			apply_filters(
-				'jetpack_sitemap_image_ns',
-				array(
-					'xmlns:xsi'          => 'http://www.w3.org/2001/XMLSchema-instance',
-					'xsi:schemaLocation' => 'http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd',
-					'xmlns'              => 'http://www.sitemaps.org/schemas/sitemap/0.9',
-					'xmlns:image'        => 'http://www.google.com/schemas/sitemap-image/1.1',
-				)
-			)
-		);
-
-		$buffer = new Jetpack_Sitemap_Buffer(
+		$buffer = new Jetpack_Sitemap_Buffer_Image(
 			JP_SITEMAP_MAX_ITEMS,
-			JP_SITEMAP_MAX_BYTES,
-			<<<HEADER
-<?xml version='1.0' encoding='UTF-8'?>
-<!-- generator='jetpack-{$jetpack_version}' -->
-<?xml-stylesheet type='text/xsl' href='{$image_sitemap_xsl_url}'?>
-<urlset{$namespaces}>\n
-HEADER
-			,
-			<<<FOOTER
-</urlset>\n
-FOOTER
-			,
-			/* epoch */
-			'1970-01-01 00:00:00'
+			JP_SITEMAP_MAX_BYTES
 		);
 
 		// Add as many items to the buffer as possible.
@@ -725,7 +654,7 @@ FOOTER
 			foreach ( $posts as $post ) {
 				$current_item = $this->image_post_to_sitemap_item( $post );
 
-				if ( true === $buffer->try_to_add_item( $current_item['xml'] ) ) {
+				if ( true === $buffer->append( $current_item['xml'] ) ) {
 					$last_post_id = $post->ID;
 					$buffer->view_time( $current_item['last_modified'] );
 				} else {
@@ -784,47 +713,9 @@ FOOTER
 			$this->logger->report( "-- Building $debug_name" );
 		}
 
-		$video_sitemap_xsl_url = $this->finder->construct_sitemap_url( 'video-sitemap.xsl' );
-
-		$jetpack_version = JETPACK__VERSION;
-
-		$namespaces = Jetpack_Sitemap_Buffer::array_to_xml_attr_string(
-			/**
-			 * Filter the XML namespaces included in video sitemaps.
-			 *
-			 * @module sitemaps
-			 *
-			 * @since 4.8.0
-			 *
-			 * @param array $namespaces Associative array with namespaces and namespace URIs.
-			 */
-			apply_filters(
-				'jetpack_sitemap_video_ns',
-				array(
-					'xmlns:xsi'          => 'http://www.w3.org/2001/XMLSchema-instance',
-					'xsi:schemaLocation' => 'http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd',
-					'xmlns'              => 'http://www.sitemaps.org/schemas/sitemap/0.9',
-					'xmlns:video'        => 'http://www.google.com/schemas/sitemap-video/1.1',
-				)
-			)
-		);
-
-		$buffer = new Jetpack_Sitemap_Buffer(
+		$buffer = new Jetpack_Sitemap_Buffer_Video(
 			JP_SITEMAP_MAX_ITEMS,
-			JP_SITEMAP_MAX_BYTES,
-			<<<HEADER
-<?xml version='1.0' encoding='UTF-8'?>
-<!-- generator='jetpack-{$jetpack_version}' -->
-<?xml-stylesheet type='text/xsl' href='{$video_sitemap_xsl_url}'?>
-<urlset{$namespaces}>\n
-HEADER
-			,
-			<<<FOOTER
-</urlset>\n
-FOOTER
-			,
-			/* epoch */
-			'1970-01-01 00:00:00'
+			JP_SITEMAP_MAX_BYTES
 		);
 
 		// Add as many items to the buffer as possible.
@@ -841,7 +732,7 @@ FOOTER
 			foreach ( $posts as $post ) {
 				$current_item = $this->video_post_to_sitemap_item( $post );
 
-				if ( true === $buffer->try_to_add_item( $current_item['xml'] ) ) {
+				if ( true === $buffer->append( $current_item['xml'] ) ) {
 					$last_post_id = $post->ID;
 					$buffer->view_time( $current_item['last_modified'] );
 				} else {
@@ -908,25 +799,9 @@ FOOTER
 			$this->logger->report( "-- Building $index_debug_name" );
 		}
 
-		$sitemap_index_xsl_url = $this->finder->construct_sitemap_url( 'sitemap-index.xsl' );
-
-		$jetpack_version = JETPACK__VERSION;
-
-		$buffer = new Jetpack_Sitemap_Buffer(
+		$buffer = new Jetpack_Sitemap_Buffer_Master(
 			JP_SITEMAP_MAX_ITEMS,
 			JP_SITEMAP_MAX_BYTES,
-			<<<HEADER
-<?xml version='1.0' encoding='UTF-8'?>
-<!-- generator='jetpack-{$jetpack_version}' -->
-<?xml-stylesheet type='text/xsl' href='{$sitemap_index_xsl_url}'?>
-<sitemapindex xmlns='http://www.sitemaps.org/schemas/sitemap/0.9'>\n
-HEADER
-			,
-			<<<FOOTER
-</sitemapindex>\n
-FOOTER
-			,
-			/* initial last_modified value */
 			$datetime
 		);
 
@@ -944,7 +819,7 @@ FOOTER
 				),
 			);
 
-			$buffer->try_to_add_item( Jetpack_Sitemap_Buffer::array_to_xml_string( $item_array ) );
+			$buffer->append( $item_array );
 		}
 
 		// Add as many items to the buffer as possible.
@@ -966,7 +841,7 @@ FOOTER
 				$current_item = $this->sitemap_row_to_index_item( (array) $post );
 
 				// Try adding this item to the buffer.
-				if ( true === $buffer->try_to_add_item( $current_item['xml'] ) ) {
+				if ( true === $buffer->append( $current_item['xml'] ) ) {
 					$last_sitemap_id = $post['ID'];
 					$buffer->view_time( $current_item['last_modified'] );
 				} else {
@@ -1023,7 +898,7 @@ FOOTER
 		);
 
 		return array(
-			'xml'           => Jetpack_Sitemap_Buffer::array_to_xml_string( $item_array ),
+			'xml'           => $item_array,
 			'last_modified' => $row['post_date'],
 		);
 	}
@@ -1046,10 +921,6 @@ FOOTER
 				$this->logger->report( 'Beginning news sitemap generation.' );
 			}
 
-			$news_sitemap_xsl_url = $this->finder->construct_sitemap_url( 'news-sitemap.xsl' );
-
-			$jetpack_version = JETPACK__VERSION;
-
 			/**
 			 * Filter limit of entries to include in news sitemap.
 			 *
@@ -1064,43 +935,9 @@ FOOTER
 				JP_NEWS_SITEMAP_MAX_ITEMS
 			);
 
-			$namespaces = Jetpack_Sitemap_Buffer::array_to_xml_attr_string(
-				/**
-				 * Filter the attribute value pairs used for namespace and namespace URI mappings.
-				 *
-				 * @module sitemaps
-				 *
-				 * @since 4.8.0
-				 *
-				 * @param array $namespaces Associative array with namespaces and namespace URIs.
-				 */
-				apply_filters(
-					'jetpack_sitemap_news_ns',
-					array(
-						'xmlns:xsi'          => 'http://www.w3.org/2001/XMLSchema-instance',
-						'xsi:schemaLocation' => 'http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd',
-						'xmlns'              => 'http://www.sitemaps.org/schemas/sitemap/0.9',
-						'xmlns:news'         => 'http://www.google.com/schemas/sitemap-news/0.9',
-					)
-				)
-			);
-
-			$buffer = new Jetpack_Sitemap_Buffer(
+			$buffer = new Jetpack_Sitemap_Buffer_News(
 				min( $item_limit, JP_NEWS_SITEMAP_MAX_ITEMS ),
-				JP_SITEMAP_MAX_BYTES,
-				<<<HEADER
-<?xml version='1.0' encoding='UTF-8'?>
-<!-- generator='jetpack-{$jetpack_version}' -->
-<?xml-stylesheet type='text/xsl' href='{$news_sitemap_xsl_url}'?>
-<urlset{$namespaces}>\n
-HEADER
-				,
-				<<<FOOTER
-</urlset>\n
-FOOTER
-				,
-				/* epoch */
-				'1970-01-01 00:00:00'
+				JP_SITEMAP_MAX_BYTES
 			);
 
 			$posts = $this->librarian->query_most_recent_posts( JP_NEWS_SITEMAP_MAX_ITEMS );
@@ -1108,7 +945,7 @@ FOOTER
 			foreach ( $posts as $post ) {
 				$current_item = $this->post_to_news_sitemap_item( $post );
 
-				if ( false === $buffer->try_to_add_item( $current_item['xml'] ) ) {
+				if ( false === $buffer->append( $current_item['xml'] ) ) {
 					break;
 				}
 			}
@@ -1124,7 +961,7 @@ FOOTER
 				$the_stored_news_sitemap,
 				JP_NEWS_SITEMAP_INTERVAL
 			);
-		}
+		} // End if().
 
 		return $the_stored_news_sitemap;
 	}
@@ -1138,7 +975,7 @@ FOOTER
 	 *
 	 * @param WP_Post $post The post to be processed.
 	 *
-	 * @return string An XML fragment representing the post URL.
+	 * @return array An array representing the post URL.
 	 */
 	private function post_to_sitemap_item( $post ) {
 
@@ -1200,7 +1037,7 @@ FOOTER
 		$item_array = apply_filters( 'jetpack_sitemap_url', $item_array, $post->ID );
 
 		return array(
-			'xml'           => Jetpack_Sitemap_Buffer::array_to_xml_string( $item_array ),
+			'xml'           => $item_array,
 			'last_modified' => $last_modified,
 		);
 	}
@@ -1236,11 +1073,11 @@ FOOTER
 			);
 		}
 
-		$url = esc_url( wp_get_attachment_url( $post->ID ) );
+		$url = wp_get_attachment_url( $post->ID );
 
-		$parent_url = esc_url( get_permalink( get_post( $post->post_parent ) ) );
+		$parent_url = get_permalink( get_post( $post->post_parent ) );
 		if ( '' == $parent_url ) { // WPCS: loose comparison ok.
-			$parent_url = esc_url( get_permalink( $post ) );
+			$parent_url = get_permalink( $post );
 		}
 
 		$item_array = array(
@@ -1252,16 +1089,9 @@ FOOTER
 				),
 			),
 		);
-		/** This filter is already documented in core/wp-includes/feed.php */
-		$title = apply_filters( 'the_title_rss', $post->post_title );
-		if ( '' !== $title ) {
-			$item_array['url']['image:image']['image:title'] = htmlentities( $title );
-		}
-		/** This filter is already documented in core/wp-includes/feed.php */
-		$caption = apply_filters( 'the_excerpt_rss', $post->post_excerpt );
-		if ( '' !== $caption ) {
-			$item_array['url']['image:image']['image:caption'] = "<![CDATA[" . $caption . "]]>";
-		}
+
+		$item_array['url']['image:image']['image:title'] = $post->post_title;
+		$item_array['url']['image:image']['image:caption'] = $post->post_excerpt;
 
 		/**
 		 * Filter associative array with data to build <url> node
@@ -1281,7 +1111,7 @@ FOOTER
 		);
 
 		return array(
-			'xml'           => Jetpack_Sitemap_Buffer::array_to_xml_string( $item_array ),
+			'xml'           => $item_array,
 			'last_modified' => $post->post_modified_gmt,
 		);
 	}
@@ -1323,11 +1153,11 @@ FOOTER
 			$parent_url = esc_url( get_permalink( $post ) );
 		}
 
-		// Prepare the content like get_the_content_feed()
+		// Prepare the content like get_the_content_feed().
 		$content = $post->post_content;
 		/** This filter is already documented in core/wp-includes/post-template.php */
 		$content = apply_filters( 'the_content', $content );
-		$content = str_replace(']]>', ']]&gt;', $content);
+
 		/** This filter is already documented in core/wp-includes/feed.php */
 		$content = apply_filters( 'the_content_feed', $content, 'rss2' );
 
@@ -1339,7 +1169,7 @@ FOOTER
 					/** This filter is already documented in core/wp-includes/feed.php */
 					'video:title'         => apply_filters( 'the_title_rss', $post->post_title ),
 					'video:thumbnail_loc' => '',
-					'video:description'   => '<![CDATA[' . $content . ']]>',
+					'video:description'   => $content,
 					'video:content_loc'   => esc_url( wp_get_attachment_url( $post->ID ) ),
 				),
 			),
@@ -1366,7 +1196,7 @@ FOOTER
 		);
 
 		return array(
-			'xml'           => Jetpack_Sitemap_Buffer::array_to_xml_string( $item_array ),
+			'xml'           => $item_array,
 			'last_modified' => $post->post_modified_gmt,
 		);
 	}
@@ -1430,7 +1260,7 @@ FOOTER
 				'lastmod' => jp_sitemap_datetime( $post->post_modified_gmt ),
 				'news:news' => array(
 					'news:publication' => array(
-						'news:name'     => esc_html( get_bloginfo( 'name' ) ),
+						'news:name'     => get_bloginfo( 'name' ),
 						'news:language' => $language,
 					),
 					/** This filter is already documented in core/wp-includes/feed.php */
@@ -1459,8 +1289,7 @@ FOOTER
 		);
 
 		return array(
-			'xml' => Jetpack_Sitemap_Buffer::array_to_xml_string( $item_array ),
+			'xml' => $item_array,
 		);
 	}
-
 }
diff --git a/plugins/jetpack/modules/sitemaps/sitemap-librarian.php b/plugins/jetpack/modules/sitemaps/sitemap-librarian.php
index ac895749..89a86830 100644
--- a/plugins/jetpack/modules/sitemaps/sitemap-librarian.php
+++ b/plugins/jetpack/modules/sitemaps/sitemap-librarian.php
@@ -39,7 +39,14 @@ class Jetpack_Sitemap_Librarian {
 	 * }
 	 */
 	public function read_sitemap_data( $name, $type ) {
-		$the_post = get_page_by_title( $name, 'OBJECT', $type );
+		$post_array = get_posts( array(
+			'numberposts' => 1,
+			'title' => $name,
+			'post_type' => $type,
+			'post_status' => 'draft'
+		) );
+
+		$the_post = array_shift( $post_array );
 
 		if ( null === $the_post ) {
 			return null;
@@ -49,15 +56,14 @@ class Jetpack_Sitemap_Librarian {
 				'timestamp' => $the_post->post_date,
 				'name'      => $the_post->post_title,
 				'type'      => $the_post->post_type,
-				'text'      => $the_post->post_content,
+				'text'      => base64_decode( $the_post->post_content ),
 			);
 		}
 	}
 
 	/**
 	 * Store a sitemap of given type and index in the database.
-	 * Note that the sitemap contents are run through esc_html before
-	 * being stored, and the timestamp reencoded as 'Y-m-d H:i:s'.
+	 * Note that the timestamp is reencoded as 'Y-m-d H:i:s'.
 	 *
 	 * If a sitemap with that type and name does not exist, create it.
 	 * If a sitemap with that type and name does exist, update it.
@@ -73,27 +79,26 @@ class Jetpack_Sitemap_Librarian {
 	public function store_sitemap_data( $index, $type, $contents, $timestamp ) {
 		$name = jp_sitemap_filename( $type, $index );
 
-		$the_post = get_page_by_title( $name, 'OBJECT', $type );
+		$the_post = $this->read_sitemap_data( $name, $type );
 
 		if ( null === $the_post ) {
 			// Post does not exist.
 			wp_insert_post(array(
 				'post_title'   => $name,
-				'post_content' => esc_html( $contents ),
+				'post_content' => base64_encode( $contents ),
 				'post_type'    => $type,
 				'post_date'    => date( 'Y-m-d H:i:s', strtotime( $timestamp ) ),
 			));
 		} else {
 			// Post does exist.
 			wp_insert_post(array(
-				'ID'           => $the_post->ID,
+				'ID'           => $the_post['id'],
 				'post_title'   => $name,
-				'post_content' => esc_html( $contents ),
+				'post_content' => base64_encode( $contents ),
 				'post_type'    => $type,
 				'post_date'    => date( 'Y-m-d H:i:s', strtotime( $timestamp ) ),
 			));
 		}
-		return;
 	}
 
 	/**
@@ -108,12 +113,12 @@ class Jetpack_Sitemap_Librarian {
 	 * @return bool 'true' if a row was deleted, 'false' otherwise.
 	 */
 	public function delete_sitemap_data( $name, $type ) {
-		$the_post = get_page_by_title( $name, 'OBJECT', $type );
+		$the_post = $this->read_sitemap_data( $name, $type );
 
 		if ( null === $the_post ) {
 			return false;
 		} else {
-			wp_delete_post( $the_post->ID );
+			wp_delete_post( $the_post['id'] );
 			return true;
 		}
 	}
@@ -137,7 +142,7 @@ class Jetpack_Sitemap_Librarian {
 		if ( null === $row ) {
 			return '';
 		} else {
-			return wp_specialchars_decode( $row['text'], ENT_QUOTES );
+			return $row['text'];
 		}
 	}
 
@@ -159,8 +164,6 @@ class Jetpack_Sitemap_Librarian {
 			$name = jp_sitemap_filename( $type, $position );
 			$any_left = $this->delete_sitemap_data( $name, $type );
 		}
-
-		return;
 	}
 
 	/**
@@ -170,35 +173,33 @@ class Jetpack_Sitemap_Librarian {
 	 * @since 4.8.0
 	 */
 	public function delete_all_stored_sitemap_data() {
-		$this->delete_sitemap_data(
-			jp_sitemap_filename( JP_MASTER_SITEMAP_TYPE ),
-			JP_MASTER_SITEMAP_TYPE
-		);
-
-		$this->delete_numbered_sitemap_rows_after(
-			0, JP_PAGE_SITEMAP_TYPE
-		);
-
-		$this->delete_numbered_sitemap_rows_after(
-			0, JP_PAGE_SITEMAP_INDEX_TYPE
-		);
-
-		$this->delete_numbered_sitemap_rows_after(
-			0, JP_IMAGE_SITEMAP_TYPE
-		);
-
-		$this->delete_numbered_sitemap_rows_after(
-			0, JP_IMAGE_SITEMAP_INDEX_TYPE
-		);
-
-		$this->delete_numbered_sitemap_rows_after(
-			0, JP_VIDEO_SITEMAP_TYPE
-		);
+		$this->delete_sitemap_type_data( JP_MASTER_SITEMAP_TYPE );
+		$this->delete_sitemap_type_data( JP_PAGE_SITEMAP_TYPE );
+		$this->delete_sitemap_type_data( JP_PAGE_SITEMAP_INDEX_TYPE );
+		$this->delete_sitemap_type_data( JP_IMAGE_SITEMAP_TYPE );
+		$this->delete_sitemap_type_data( JP_IMAGE_SITEMAP_INDEX_TYPE );
+		$this->delete_sitemap_type_data( JP_VIDEO_SITEMAP_TYPE );
+		$this->delete_sitemap_type_data( JP_VIDEO_SITEMAP_INDEX_TYPE );
+	}
 
-		$this->delete_numbered_sitemap_rows_after(
-			0, JP_VIDEO_SITEMAP_INDEX_TYPE
-		);
-		return;
+	/**
+	 * Deletes all sitemap data of specific type
+	 *
+	 * @access protected
+	 * @since 5.3.0
+	 *
+	 * @param String $type
+	 */
+	protected function delete_sitemap_type_data( $type ) {
+		$ids = get_posts( array(
+			'post_type' => $type,
+			'post_status' => 'draft',
+			'fields' => 'ids'
+		) );
+
+		foreach( $ids as $id ) {
+			wp_trash_post( $id );
+		}
 	}
 
 	/**
diff --git a/plugins/jetpack/modules/sitemaps/sitemaps.php b/plugins/jetpack/modules/sitemaps/sitemaps.php
index 3620957c..2c433a1d 100644
--- a/plugins/jetpack/modules/sitemaps/sitemaps.php
+++ b/plugins/jetpack/modules/sitemaps/sitemaps.php
@@ -108,6 +108,12 @@ class Jetpack_Sitemap_Manager {
 			10
 		);
 
+		// In case we need to purge all sitemaps, we do this.
+		add_action(
+			'jetpack_sitemaps_purge_data',
+			array( $this, 'callback_action_purge_data' )
+		);
+
 		/*
 		 * Module parameters are stored as options in the database.
 		 * This allows us to avoid having to process all of init
@@ -434,6 +440,17 @@ class Jetpack_Sitemap_Manager {
 	}
 
 	/**
+	 * Callback for resetting stored sitemap data.
+	 *
+	 * @access public
+	 * @since 5.3.0
+	 */
+	public function callback_action_purge_data() {
+		$this->callback_action_flush_news_sitemap_cache();
+		$this->librarian->delete_all_stored_sitemap_data();
+	}
+
+	/**
 	 * Callback to set the sitemap location.
 	 *
 	 * @access public