<?php // phpcs:ignore WordPress.Files.FileName.InvalidClassFileName
* XMLWriter implementation of the sitemap buffer.
* @package automattic/jetpack
if ( ! defined( 'ABSPATH' ) ) {
* A buffer for constructing sitemap xml files using XMLWriter.
abstract class Jetpack_Sitemap_Buffer_XMLWriter {
* Largest number of items the buffer can hold.
* @var int $item_capacity The item capacity.
protected $item_capacity;
* Largest number of bytes the buffer can hold.
* @var int $byte_capacity The byte capacity.
protected $byte_capacity;
* Flag which detects when the buffer is full.
* @var bool $is_full_flag The flag value.
* Flag which detects when the buffer is empty.
* Set true on construction and flipped to false only after a successful append.
protected $is_empty_flag = true;
* The most recent timestamp seen by the buffer.
* @var string $timestamp Must be in 'YYYY-MM-DD hh:mm:ss' format.
* The XMLWriter instance used to construct the XML.
* Helper class to construct sitemap paths.
* @var Jetpack_Sitemap_Finder
* The XML content chunks collected from XMLWriter.
* Collect chunks and join once at the end to reduce string reallocations
* and improve performance on large sitemaps.
protected $chunks = array();
* Tracks whether the root element has been started.
protected $root_started = false;
* Mirror DOMDocument built on-demand for jetpack_print_sitemap compatibility.
protected $dom_document = null;
* Tracks whether XMLWriter document has been finalized (closed and flushed).
protected $is_finalized = false;
* Construct a new Jetpack_Sitemap_Buffer_XMLWriter.
* @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 $time The initial datetime of the buffer. Must be in 'YYYY-MM-DD hh:mm:ss' format.
public function __construct( $item_limit, $byte_limit, $time ) {
$this->is_full_flag = false;
$this->is_empty_flag = true;
$this->timestamp = $time;
$this->finder = new Jetpack_Sitemap_Finder();
$this->writer = new XMLWriter();
$this->writer->openMemory();
$this->writer->setIndent( true );
$this->writer->startDocument( '1.0', 'UTF-8' );
$this->item_capacity = max( 1, (int) $item_limit );
$this->byte_capacity = max( 1, (int) $byte_limit );
// Capture and account the XML declaration bytes to mirror DOM behavior.
$declaration = $this->writer->outputMemory( true );
$this->chunks[] = $declaration;
$this->byte_capacity -= strlen( $declaration );
// Allow subclasses to write comments and processing instructions only.
$this->initialize_buffer();
// Capture pre-root bytes (comments/PI). Do not subtract from capacity.
$pre_root_output = $this->writer->outputMemory( true );
$this->chunks[] = $pre_root_output;
* Initialize the buffer with any required headers or setup.
* This should be implemented by child classes.
abstract protected function initialize_buffer();
* Start the root element (e.g., urlset or sitemapindex) and write its attributes.
* Implemented by subclasses.
abstract protected function start_root();
* Ensure the root element has been started and account its bytes once.
protected function ensure_root_started() {
if ( $this->root_started ) {
$root_chunk = $this->writer->outputMemory( true );
$this->chunks[] = $root_chunk;
$this->byte_capacity -= strlen( $root_chunk );
$this->root_started = true;
* Finalize writer output once by closing the root and document and flushing.
protected function finalize_writer_output() {
if ( $this->is_finalized ) {
$this->ensure_root_started();
$this->writer->endElement(); // End root element (urlset/sitemapindex)
$this->writer->endDocument();
$final_content = $this->writer->outputMemory( true );
$this->chunks[] = $final_content;
$this->is_finalized = true;
* Append an item to the buffer.
* @param array $array The item to be added.
* @return bool True if the append succeeded, False if not.
public function append( $array ) {
if ( $this->is_full_flag ) {
if ( 0 >= $this->item_capacity || 0 >= $this->byte_capacity ) {
$this->is_full_flag = true;
// Ensure root is started on first append and account its bytes.
$this->ensure_root_started();
// Attempt to render the item. Subclasses may decide to skip writing
// if the input structure is invalid for that sitemap type.
$this->append_item( $array );
// Capture only the bytes produced by this item.
$new_content = $this->writer->outputMemory( true );
// If nothing was written, treat as a no-op: keep the buffer "empty"
// and do not consume item/byte capacities.
if ( '' === $new_content ) {
// Persist newly written bytes and update capacities.
$this->chunks[] = $new_content;
$this->item_capacity -= 1;
$this->byte_capacity -= strlen( $new_content );
$this->is_empty_flag = false;
// Check both capacity limits.
if ( 0 >= $this->item_capacity || $this->byte_capacity <= 0 ) {
$this->is_full_flag = true;
* Append a specific item to the buffer.
* This should be implemented by child classes.
* @param array $array The item to be added.
abstract protected function append_item( $array );
* Recursively writes XML elements from an associative array.
* This method iterates through an array and writes XML elements using the XMLWriter instance.
* If a value in the array is itself an array, it calls itself recursively.
* @param array $data The array to convert to XML.
protected function array_to_xml( $data ) {
foreach ( (array) $data as $tag => $value ) {
if ( is_array( $value ) ) {
$this->writer->startElement( $tag );
$this->array_to_xml( $value );
$this->writer->endElement();
// Write raw text; XMLWriter will escape XML-reserved chars, matching DOMDocument behavior.
$this->writer->writeElement( $tag, (string) $value );
* Retrieve the contents of the buffer.
* @return string The contents of the buffer.
public function contents() {
$this->finalize_writer_output();
if ( $this->dom_document instanceof DOMDocument ) {
return $this->dom_document->saveXML();
if ( empty( $this->chunks ) ) {
// If buffer is empty, return a minimal valid XML structure
return "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<urlset xmlns=\"http://www.sitemaps.org/schemas/sitemap/0.9\"></urlset>";
return implode( '', $this->chunks );
* Detect whether the buffer is full.
* @return bool True if the buffer is full, false otherwise.
public function is_full() {
return $this->is_full_flag;
* Detect whether the buffer is empty.
* @return bool True if the buffer is empty, false otherwise.
public function is_empty() {
return $this->is_empty_flag;
* Update the timestamp of the buffer.
* @param string $new_time A datetime string in 'YYYY-MM-DD hh:mm:ss' format.
public function view_time( $new_time ) {
$this->timestamp = max( $this->timestamp, $new_time );
* Retrieve the timestamp of the buffer.
* @return string A datetime string in 'YYYY-MM-DD hh:mm:ss' format.
public function last_modified() {
* Compatibility method for the old DOMDocument implementation.
* This is only here to satisfy the jetpack_print_sitemap filter.
* @return DOMDocument DOM representation of the current sitemap contents.
public function get_document() {
if ( $this->dom_document instanceof DOMDocument ) {
return $this->dom_document;
$this->finalize_writer_output();
$dom = new DOMDocument( '1.0', 'UTF-8' );
$dom->formatOutput = true; // phpcs:ignore WordPress.NamingConventions.ValidVariableName.UsedPropertyNotSnakeCase
$dom->preserveWhiteSpace = false; // phpcs:ignore WordPress.NamingConventions.ValidVariableName.UsedPropertyNotSnakeCase
// Load current XML content into DOM for compatibility with filters.
@$dom->loadXML( implode( '', $this->chunks ) ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged -- Avoid fatal on unexpected content
$this->dom_document = $dom;
return $this->dom_document;
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