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[mediawiki.git] / includes / Export.php

<?php
/**
 * Base classes for dumps and export
 *
 * Copyright © 2003, 2005, 2006 Brion Vibber <brion@pobox.com>
 * http://www.mediawiki.org/
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 */

/**
 * @defgroup Dump Dump
 */

/**
 * @ingroup SpecialPage Dump
 */
class WikiExporter {
        var $list_authors = false ; # Return distinct author list (when not returning full history)
        var $author_list = "" ;

        var $dumpUploads = false;
        var $dumpUploadFileContents = false;

        const FULL = 1;
        const CURRENT = 2;
        const STABLE = 4; // extension defined
        const LOGS = 8;
        const RANGE = 16;

        const BUFFER = 0;
        const STREAM = 1;

        const TEXT = 0;
        const STUB = 1;

        var $buffer;

        var $text;

        /**
         * @var DumpOutput
         */
        var $sink;

        /**
         * If using WikiExporter::STREAM to stream a large amount of data,
         * provide a database connection which is not managed by
         * LoadBalancer to read from: some history blob types will
         * make additional queries to pull source data while the
         * main query is still running.
         *
         * @param $db DatabaseBase
         * @param $history Mixed: one of WikiExporter::FULL, WikiExporter::CURRENT,
         *                 WikiExporter::RANGE or WikiExporter::STABLE,
         *                 or an associative array:
         *                   offset: non-inclusive offset at which to start the query
         *                   limit: maximum number of rows to return
         *                   dir: "asc" or "desc" timestamp order
         * @param $buffer Int: one of WikiExporter::BUFFER or WikiExporter::STREAM
         * @param $text Int: one of WikiExporter::TEXT or WikiExporter::STUB
         */
        function __construct( &$db, $history = WikiExporter::CURRENT,
                        $buffer = WikiExporter::BUFFER, $text = WikiExporter::TEXT ) {
                $this->db =& $db;
                $this->history = $history;
                $this->buffer  = $buffer;
                $this->writer  = new XmlDumpWriter();
                $this->sink    = new DumpOutput();
                $this->text    = $text;
        }

        /**
         * Set the DumpOutput or DumpFilter object which will receive
         * various row objects and XML output for filtering. Filters
         * can be chained or used as callbacks.
         *
         * @param $sink mixed
         */
        public function setOutputSink( &$sink ) {
                $this->sink =& $sink;
        }

        public function openStream() {
                $output = $this->writer->openStream();
                $this->sink->writeOpenStream( $output );
        }

        public function closeStream() {
                $output = $this->writer->closeStream();
                $this->sink->writeCloseStream( $output );
        }

        /**
         * Dumps a series of page and revision records for all pages
         * in the database, either including complete history or only
         * the most recent version.
         */
        public function allPages() {
                $this->dumpFrom( '' );
        }

        /**
         * Dumps a series of page and revision records for those pages
         * in the database falling within the page_id range given.
         * @param $start Int: inclusive lower limit (this id is included)
         * @param $end   Int: Exclusive upper limit (this id is not included)
         *                   If 0, no upper limit.
         */
        public function pagesByRange( $start, $end ) {
                $condition = 'page_id >= ' . intval( $start );
                if ( $end ) {
                        $condition .= ' AND page_id < ' . intval( $end );
                }
                $this->dumpFrom( $condition );
        }

        /**
         * Dumps a series of page and revision records for those pages
         * in the database with revisions falling within the rev_id range given.
         * @param $start Int: inclusive lower limit (this id is included)
         * @param $end   Int: Exclusive upper limit (this id is not included)
         *                   If 0, no upper limit.
         */
        public function revsByRange( $start, $end ) {
                $condition = 'rev_id >= ' . intval( $start );
                if ( $end ) {
                        $condition .= ' AND rev_id < ' . intval( $end );
                }
                $this->dumpFrom( $condition );
        }

        /**
         * @param $title Title
         */
        public function pageByTitle( $title ) {
                $this->dumpFrom(
                        'page_namespace=' . $title->getNamespace() .
                        ' AND page_title=' . $this->db->addQuotes( $title->getDBkey() ) );
        }

        /**
         * @param $name string
         * @throws MWException
         */
        public function pageByName( $name ) {
                $title = Title::newFromText( $name );
                if ( is_null( $title ) ) {
                        throw new MWException( "Can't export invalid title" );
                } else {
                        $this->pageByTitle( $title );
                }
        }

        /**
         * @param $names array
         */
        public function pagesByName( $names ) {
                foreach ( $names as $name ) {
                        $this->pageByName( $name );
                }
        }

        public function allLogs() {
                $this->dumpFrom( '' );
        }

        /**
         * @param $start int
         * @param $end int
         */
        public function logsByRange( $start, $end ) {
                $condition = 'log_id >= ' . intval( $start );
                if ( $end ) {
                        $condition .= ' AND log_id < ' . intval( $end );
                }
                $this->dumpFrom( $condition );
        }

        /**
         * Generates the distinct list of authors of an article
         * Not called by default (depends on $this->list_authors)
         * Can be set by Special:Export when not exporting whole history
         *
         * @param $cond
         */
        protected function do_list_authors( $cond ) {
                wfProfileIn( __METHOD__ );
                $this->author_list = "<contributors>";
                // rev_deleted

                $res = $this->db->select(
                        array( 'page', 'revision' ),
                        array( 'DISTINCT rev_user_text', 'rev_user' ),
                        array(
                                $this->db->bitAnd( 'rev_deleted', Revision::DELETED_USER ) . ' = 0',
                                $cond,
                                'page_id = rev_id',
                        ),
                        __METHOD__
                );

                foreach ( $res as $row ) {
                        $this->author_list .= "<contributor>" .
                                "<username>" .
                                htmlentities( $row->rev_user_text )  .
                                "</username>" .
                                "<id>" .
                                $row->rev_user .
                                "</id>" .
                                "</contributor>";
                }
                $this->author_list .= "</contributors>";
                wfProfileOut( __METHOD__ );
        }

        /**
         * @param $cond string
         * @throws MWException
         * @throws Exception
         */
        protected function dumpFrom( $cond = '' ) {
                wfProfileIn( __METHOD__ );
                # For logging dumps...
                if ( $this->history & self::LOGS ) {
                        $where = array( 'user_id = log_user' );
                        # Hide private logs
                        $hideLogs = LogEventsList::getExcludeClause( $this->db );
                        if ( $hideLogs ) $where[] = $hideLogs;
                        # Add on any caller specified conditions
                        if ( $cond ) $where[] = $cond;
                        # Get logging table name for logging.* clause
                        $logging = $this->db->tableName( 'logging' );

                        if ( $this->buffer == WikiExporter::STREAM ) {
                                $prev = $this->db->bufferResults( false );
                        }
                        $wrapper = null; // Assuring $wrapper is not undefined, if exception occurs early
                        try {
                                $result = $this->db->select( array( 'logging', 'user' ),
                                        array( "{$logging}.*", 'user_name' ), // grab the user name
                                        $where,
                                        __METHOD__,
                                        array( 'ORDER BY' => 'log_id', 'USE INDEX' => array( 'logging' => 'PRIMARY' ) )
                                );
                                $wrapper = $this->db->resultObject( $result );
                                $this->outputLogStream( $wrapper );
                                if ( $this->buffer == WikiExporter::STREAM ) {
                                        $this->db->bufferResults( $prev );
                                }
                        } catch ( Exception $e ) {
                                // Throwing the exception does not reliably free the resultset, and
                                // would also leave the connection in unbuffered mode.

                                // Freeing result
                                try {
                                        if ( $wrapper ) {
                                                $wrapper->free();
                                        }
                                } catch ( Exception $e2 ) {
                                        // Already in panic mode -> ignoring $e2 as $e has
                                        // higher priority
                                }

                                // Putting database back in previous buffer mode
                                try {
                                        if ( $this->buffer == WikiExporter::STREAM ) {
                                                $this->db->bufferResults( $prev );
                                        }
                                } catch ( Exception $e2 ) {
                                        // Already in panic mode -> ignoring $e2 as $e has
                                        // higher priority
                                }

                                // Inform caller about problem
                                throw $e;
                        }
                # For page dumps...
                } else {
                        $tables = array( 'page', 'revision' );
                        $opts = array( 'ORDER BY' => 'page_id ASC' );
                        $opts['USE INDEX'] = array();
                        $join = array();
                        if ( is_array( $this->history ) ) {
                                # Time offset/limit for all pages/history...
                                $revJoin = 'page_id=rev_page';
                                # Set time order
                                if ( $this->history['dir'] == 'asc' ) {
                                        $op = '>';
                                        $opts['ORDER BY'] = 'rev_timestamp ASC';
                                } else {
                                        $op = '<';
                                        $opts['ORDER BY'] = 'rev_timestamp DESC';
                                }
                                # Set offset
                                if ( !empty( $this->history['offset'] ) ) {
                                        $revJoin .= " AND rev_timestamp $op " .
                                                $this->db->addQuotes( $this->db->timestamp( $this->history['offset'] ) );
                                }
                                $join['revision'] = array( 'INNER JOIN', $revJoin );
                                # Set query limit
                                if ( !empty( $this->history['limit'] ) ) {
                                        $opts['LIMIT'] = intval( $this->history['limit'] );
                                }
                        } elseif ( $this->history & WikiExporter::FULL ) {
                                # Full history dumps...
                                $join['revision'] = array( 'INNER JOIN', 'page_id=rev_page' );
                        } elseif ( $this->history & WikiExporter::CURRENT ) {
                                # Latest revision dumps...
                                if ( $this->list_authors && $cond != '' )  { // List authors, if so desired
                                        $this->do_list_authors( $cond );
                                }
                                $join['revision'] = array( 'INNER JOIN', 'page_id=rev_page AND page_latest=rev_id' );
                        } elseif ( $this->history & WikiExporter::STABLE ) {
                                # "Stable" revision dumps...
                                # Default JOIN, to be overridden...
                                $join['revision'] = array( 'INNER JOIN', 'page_id=rev_page AND page_latest=rev_id' );
                                # One, and only one hook should set this, and return false
                                if ( wfRunHooks( 'WikiExporter::dumpStableQuery', array( &$tables, &$opts, &$join ) ) ) {
                                        wfProfileOut( __METHOD__ );
                                        throw new MWException( __METHOD__ . " given invalid history dump type." );
                                }
                        } elseif ( $this->history & WikiExporter::RANGE ) {
                                # Dump of revisions within a specified range
                                $join['revision'] = array( 'INNER JOIN', 'page_id=rev_page' );
                                $opts['ORDER BY'] = array( 'rev_page ASC', 'rev_id ASC' );
                        } else {
                                # Uknown history specification parameter?
                                wfProfileOut( __METHOD__ );
                                throw new MWException( __METHOD__ . " given invalid history dump type." );
                        }
                        # Query optimization hacks
                        if ( $cond == '' ) {
                                $opts[] = 'STRAIGHT_JOIN';
                                $opts['USE INDEX']['page'] = 'PRIMARY';
                        }
                        # Build text join options
                        if ( $this->text != WikiExporter::STUB ) { // 1-pass
                                $tables[] = 'text';
                                $join['text'] = array( 'INNER JOIN', 'rev_text_id=old_id' );
                        }

                        if ( $this->buffer == WikiExporter::STREAM ) {
                                $prev = $this->db->bufferResults( false );
                        }

                        $wrapper = null; // Assuring $wrapper is not undefined, if exception occurs early
                        try {
                                wfRunHooks( 'ModifyExportQuery',
                                                array( $this->db, &$tables, &$cond, &$opts, &$join ) );

                                # Do the query!
                                $result = $this->db->select( $tables, '*', $cond, __METHOD__, $opts, $join );
                                $wrapper = $this->db->resultObject( $result );
                                # Output dump results
                                $this->outputPageStream( $wrapper );

                                if ( $this->buffer == WikiExporter::STREAM ) {
                                        $this->db->bufferResults( $prev );
                                }
                        } catch ( Exception $e ) {
                                // Throwing the exception does not reliably free the resultset, and
                                // would also leave the connection in unbuffered mode.

                                // Freeing result
                                try {
                                        if ( $wrapper ) {
                                                $wrapper->free();
                                        }
                                } catch ( Exception $e2 ) {
                                        // Already in panic mode -> ignoring $e2 as $e has
                                        // higher priority
                                }

                                // Putting database back in previous buffer mode
                                try {
                                        if ( $this->buffer == WikiExporter::STREAM ) {
                                                $this->db->bufferResults( $prev );
                                        }
                                } catch ( Exception $e2 ) {
                                        // Already in panic mode -> ignoring $e2 as $e has
                                        // higher priority
                                }

                                // Inform caller about problem
                                throw $e;
                        }
                }
                wfProfileOut( __METHOD__ );
        }

        /**
         * Runs through a query result set dumping page and revision records.
         * The result set should be sorted/grouped by page to avoid duplicate
         * page records in the output.
         *
         * Should be safe for
         * streaming (non-buffered) queries, as long as it was made on a
         * separate database connection not managed by LoadBalancer; some
         * blob storage types will make queries to pull source data.
         *
         * @param $resultset ResultWrapper
         */
        protected function outputPageStream( $resultset ) {
                $last = null;
                foreach ( $resultset as $row ) {
                        if ( is_null( $last ) ||
                                $last->page_namespace != $row->page_namespace ||
                                $last->page_title     != $row->page_title ) {
                                if ( isset( $last ) ) {
                                        $output = '';
                                        if ( $this->dumpUploads ) {
                                                $output .= $this->writer->writeUploads( $last, $this->dumpUploadFileContents );
                                        }
                                        $output .= $this->writer->closePage();
                                        $this->sink->writeClosePage( $output );
                                }
                                $output = $this->writer->openPage( $row );
                                $this->sink->writeOpenPage( $row, $output );
                                $last = $row;
                        }
                        $output = $this->writer->writeRevision( $row );
                        $this->sink->writeRevision( $row, $output );
                }
                if ( isset( $last ) ) {
                        $output = '';
                        if ( $this->dumpUploads ) {
                                $output .= $this->writer->writeUploads( $last, $this->dumpUploadFileContents );
                        }
                        $output .= $this->author_list;
                        $output .= $this->writer->closePage();
                        $this->sink->writeClosePage( $output );
                }
        }

        /**
         * @param $resultset array
         */
        protected function outputLogStream( $resultset ) {
                foreach ( $resultset as $row ) {
                        $output = $this->writer->writeLogItem( $row );
                        $this->sink->writeLogItem( $row, $output );
                }
        }
}

/**
 * @ingroup Dump
 */
class XmlDumpWriter {
        /**
         * Returns the export schema version.
         * @return string
         */
        function schemaVersion() {
                return "0.7";
        }

        /**
         * Opens the XML output stream's root <mediawiki> element.
         * This does not include an xml directive, so is safe to include
         * as a subelement in a larger XML stream. Namespace and XML Schema
         * references are included.
         *
         * Output will be encoded in UTF-8.
         *
         * @return string
         */
        function openStream() {
                global $wgLanguageCode;
                $ver = $this->schemaVersion();
                return Xml::element( 'mediawiki', array(
                        'xmlns'              => "http://www.mediawiki.org/xml/export-$ver/",
                        'xmlns:xsi'          => "http://www.w3.org/2001/XMLSchema-instance",
                        'xsi:schemaLocation' => "http://www.mediawiki.org/xml/export-$ver/ " .
                                                "http://www.mediawiki.org/xml/export-$ver.xsd",
                        'version'            => $ver,
                        'xml:lang'           => $wgLanguageCode ),
                        null ) .
                        "\n" .
                        $this->siteInfo();
        }

        /**
         * @return string
         */
        function siteInfo() {
                $info = array(
                        $this->sitename(),
                        $this->homelink(),
                        $this->generator(),
                        $this->caseSetting(),
                        $this->namespaces() );
                return "  <siteinfo>\n    " .
                        implode( "\n    ", $info ) .
                        "\n  </siteinfo>\n";
        }

        /**
         * @return string
         */
        function sitename() {
                global $wgSitename;
                return Xml::element( 'sitename', array(), $wgSitename );
        }

        /**
         * @return string
         */
        function generator() {
                global $wgVersion;
                return Xml::element( 'generator', array(), "MediaWiki $wgVersion" );
        }

        /**
         * @return string
         */
        function homelink() {
                return Xml::element( 'base', array(), Title::newMainPage()->getCanonicalUrl() );
        }

        /**
         * @return string
         */
        function caseSetting() {
                global $wgCapitalLinks;
                // "case-insensitive" option is reserved for future
                $sensitivity = $wgCapitalLinks ? 'first-letter' : 'case-sensitive';
                return Xml::element( 'case', array(), $sensitivity );
        }

        /**
         * @return string
         */
        function namespaces() {
                global $wgContLang;
                $spaces = "<namespaces>\n";
                foreach ( $wgContLang->getFormattedNamespaces() as $ns => $title ) {
                        $spaces .= '      ' .
                                Xml::element( 'namespace',
                                        array(  'key' => $ns,
                                                        'case' => MWNamespace::isCapitalized( $ns ) ? 'first-letter' : 'case-sensitive',
                                        ), $title ) . "\n";
                }
                $spaces .= "    </namespaces>";
                return $spaces;
        }

        /**
         * Closes the output stream with the closing root element.
         * Call when finished dumping things.
         *
         * @return string
         */
        function closeStream() {
                return "</mediawiki>\n";
        }

        /**
         * Opens a <page> section on the output stream, with data
         * from the given database row.
         *
         * @param $row object
         * @return string
         * @access private
         */
        function openPage( $row ) {
                $out = "  <page>\n";
                $title = Title::makeTitle( $row->page_namespace, $row->page_title );
                $out .= '    ' . Xml::elementClean( 'title', array(), self::canonicalTitle( $title ) ) . "\n";
                $out .= '    ' . Xml::element( 'ns', array(), strval( $row->page_namespace) ) . "\n";
                $out .= '    ' . Xml::element( 'id', array(), strval( $row->page_id ) ) . "\n";
                if ( $row->page_is_redirect ) {
                        $page = WikiPage::factory( $title );
                        $redirect = $page->getRedirectTarget();
                        if ( $redirect instanceOf Title && $redirect->isValidRedirectTarget() ) {
                                $out .= '    ' . Xml::element( 'redirect', array( 'title' => self::canonicalTitle( $redirect ) ) ) . "\n";
                        }
                }

                if ( $row->page_restrictions != '' ) {
                        $out .= '    ' . Xml::element( 'restrictions', array(),
                                strval( $row->page_restrictions ) ) . "\n";
                }

                wfRunHooks( 'XmlDumpWriterOpenPage', array( $this, &$out, $row, $title ) );

                return $out;
        }

        /**
         * Closes a <page> section on the output stream.
         *
         * @access private
         * @return string
         */
        function closePage() {
                return "  </page>\n";
        }

        /**
         * Dumps a <revision> section on the output stream, with
         * data filled in from the given database row.
         *
         * @param $row object
         * @return string
         * @access private
         */
        function writeRevision( $row ) {
                wfProfileIn( __METHOD__ );

                $out  = "    <revision>\n";
                $out .= "      " . Xml::element( 'id', null, strval( $row->rev_id ) ) . "\n";

                $out .= $this->writeTimestamp( $row->rev_timestamp );

                if ( $row->rev_deleted & Revision::DELETED_USER ) {
                        $out .= "      " . Xml::element( 'contributor', array( 'deleted' => 'deleted' ) ) . "\n";
                } else {
                        $out .= $this->writeContributor( $row->rev_user, $row->rev_user_text );
                }

                if ( $row->rev_minor_edit ) {
                        $out .=  "      <minor/>\n";
                }
                if ( $row->rev_deleted & Revision::DELETED_COMMENT ) {
                        $out .= "      " . Xml::element( 'comment', array( 'deleted' => 'deleted' ) ) . "\n";
                } elseif ( $row->rev_comment != '' ) {
                        $out .= "      " . Xml::elementClean( 'comment', array(), strval( $row->rev_comment ) ) . "\n";
                }

                if ( $row->rev_sha1 && !( $row->rev_deleted & Revision::DELETED_TEXT ) ) {
                        $out .= "      " . Xml::element('sha1', null, strval( $row->rev_sha1 ) ) . "\n";
                } else {
                        $out .= "      <sha1/>\n";
                }

                $text = '';
                if ( $row->rev_deleted & Revision::DELETED_TEXT ) {
                        $out .= "      " . Xml::element( 'text', array( 'deleted' => 'deleted' ) ) . "\n";
                } elseif ( isset( $row->old_text ) ) {
                        // Raw text from the database may have invalid chars
                        $text = strval( Revision::getRevisionText( $row ) );
                        $out .= "      " . Xml::elementClean( 'text',
                                array( 'xml:space' => 'preserve', 'bytes' => intval( $row->rev_len ) ),
                                strval( $text ) ) . "\n";
                } else {
                        // Stub output
                        $out .= "      " . Xml::element( 'text',
                                array( 'id' => $row->rev_text_id, 'bytes' => intval( $row->rev_len ) ),
                                "" ) . "\n";
                }

                wfRunHooks( 'XmlDumpWriterWriteRevision', array( &$this, &$out, $row, $text ) );

                $out .= "    </revision>\n";

                wfProfileOut( __METHOD__ );
                return $out;
        }

        /**
         * Dumps a <logitem> section on the output stream, with
         * data filled in from the given database row.
         *
         * @param $row object
         * @return string
         * @access private
         */
        function writeLogItem( $row ) {
                wfProfileIn( __METHOD__ );

                $out  = "  <logitem>\n";
                $out .= "    " . Xml::element( 'id', null, strval( $row->log_id ) ) . "\n";

                $out .= $this->writeTimestamp( $row->log_timestamp, "    " );

                if ( $row->log_deleted & LogPage::DELETED_USER ) {
                        $out .= "    " . Xml::element( 'contributor', array( 'deleted' => 'deleted' ) ) . "\n";
                } else {
                        $out .= $this->writeContributor( $row->log_user, $row->user_name, "    " );
                }

                if ( $row->log_deleted & LogPage::DELETED_COMMENT ) {
                        $out .= "    " . Xml::element( 'comment', array( 'deleted' => 'deleted' ) ) . "\n";
                } elseif ( $row->log_comment != '' ) {
                        $out .= "    " . Xml::elementClean( 'comment', null, strval( $row->log_comment ) ) . "\n";
                }

                $out .= "    " . Xml::element( 'type', null, strval( $row->log_type ) ) . "\n";
                $out .= "    " . Xml::element( 'action', null, strval( $row->log_action ) ) . "\n";

                if ( $row->log_deleted & LogPage::DELETED_ACTION ) {
                        $out .= "    " . Xml::element( 'text', array( 'deleted' => 'deleted' ) ) . "\n";
                } else {
                        $title = Title::makeTitle( $row->log_namespace, $row->log_title );
                        $out .= "    " . Xml::elementClean( 'logtitle', null, self::canonicalTitle( $title ) ) . "\n";
                        $out .= "    " . Xml::elementClean( 'params',
                                array( 'xml:space' => 'preserve' ),
                                strval( $row->log_params ) ) . "\n";
                }

                $out .= "  </logitem>\n";

                wfProfileOut( __METHOD__ );
                return $out;
        }

        /**
         * @param $timestamp string
         * @return string
         */
        function writeTimestamp( $timestamp, $indent = "      " ) {
                $ts = wfTimestamp( TS_ISO_8601, $timestamp );
                return $indent . Xml::element( 'timestamp', null, $ts ) . "\n";
        }

        /**
         * @param $id
         * @param $text string
         * @return string
         */
        function writeContributor( $id, $text, $indent = "      " ) {
                $out = $indent . "<contributor>\n";
                if ( $id || !IP::isValid( $text ) ) {
                        $out .= $indent . "  " . Xml::elementClean( 'username', null, strval( $text ) ) . "\n";
                        $out .= $indent . "  " . Xml::element( 'id', null, strval( $id ) ) . "\n";
                } else {
                        $out .= $indent . "  " . Xml::elementClean( 'ip', null, strval( $text ) ) . "\n";
                }
                $out .= $indent . "</contributor>\n";
                return $out;
        }

        /**
         * Warning! This data is potentially inconsistent. :(
         * @param $row
         * @param $dumpContents bool
         * @return string
         */
        function writeUploads( $row, $dumpContents = false ) {
                if ( $row->page_namespace == NS_IMAGE ) {
                        $img = wfLocalFile( $row->page_title );
                        if ( $img && $img->exists() ) {
                                $out = '';
                                foreach ( array_reverse( $img->getHistory() ) as $ver ) {
                                        $out .= $this->writeUpload( $ver, $dumpContents );
                                }
                                $out .= $this->writeUpload( $img, $dumpContents );
                                return $out;
                        }
                }
                return '';
        }

        /**
         * @param $file File
         * @param $dumpContents bool
         * @return string
         */
        function writeUpload( $file, $dumpContents = false ) {
                if ( $file->isOld() ) {
                        $archiveName = "      " .
                                Xml::element( 'archivename', null, $file->getArchiveName() ) . "\n";
                } else {
                        $archiveName = '';
                }
                if ( $dumpContents ) {
                        # Dump file as base64
                        # Uses only XML-safe characters, so does not need escaping
                        $contents = '      <contents encoding="base64">' .
                                chunk_split( base64_encode( file_get_contents( $file->getPath() ) ) ) .
                                "      </contents>\n";
                } else {
                        $contents = '';
                }
                if ( $file->isDeleted( File::DELETED_COMMENT ) ) {
                        $comment = Xml::element( 'comment', array( 'deleted' => 'deleted' ) );
                } else {
                        $comment = Xml::elementClean( 'comment', null, $file->getDescription() );
                }
                return "    <upload>\n" .
                        $this->writeTimestamp( $file->getTimestamp() ) .
                        $this->writeContributor( $file->getUser( 'id' ), $file->getUser( 'text' ) ) .
                        "      " . $comment . "\n" .
                        "      " . Xml::element( 'filename', null, $file->getName() ) . "\n" .
                        $archiveName .
                        "      " . Xml::element( 'src', null, $file->getCanonicalUrl() ) . "\n" .
                        "      " . Xml::element( 'size', null, $file->getSize() ) . "\n" .
                        "      " . Xml::element( 'sha1base36', null, $file->getSha1() ) . "\n" .
                        "      " . Xml::element( 'rel', null, $file->getRel() ) . "\n" .
                        $contents .
                        "    </upload>\n";
        }

        /**
         * Return prefixed text form of title, but using the content language's
         * canonical namespace. This skips any special-casing such as gendered
         * user namespaces -- which while useful, are not yet listed in the
         * XML <siteinfo> data so are unsafe in export.
         *
         * @param Title $title
         * @return string
         * @since 1.18
         */
        public static function canonicalTitle( Title $title ) {
                if ( $title->getInterwiki() ) {
                        return $title->getPrefixedText();
                }

                global $wgContLang;
                $prefix = str_replace( '_', ' ', $wgContLang->getNsText( $title->getNamespace() ) );

                if ( $prefix !== '' ) {
                        $prefix .= ':';
                }

                return $prefix . $title->getText();
        }
}


/**
 * Base class for output stream; prints to stdout or buffer or whereever.
 * @ingroup Dump
 */
class DumpOutput {

        /**
         * @param $string string
         */
        function writeOpenStream( $string ) {
                $this->write( $string );
        }

        /**
         * @param $string string
         */
        function writeCloseStream( $string ) {
                $this->write( $string );
        }

        /**
         * @param $page
         * @param $string string
         */
        function writeOpenPage( $page, $string ) {
                $this->write( $string );
        }

        /**
         * @param $string string
         */
        function writeClosePage( $string ) {
                $this->write( $string );
        }

        /**
         * @param $rev
         * @param $string string
         */
        function writeRevision( $rev, $string ) {
                $this->write( $string );
        }

        /**
         * @param $rev
         * @param $string string
         */
        function writeLogItem( $rev, $string ) {
                $this->write( $string );
        }

        /**
         * Override to write to a different stream type.
         * @param $string string
         * @return bool
         */
        function write( $string ) {
                print $string;
        }

        /**
         * Close the old file, move it to a specified name,
         * and reopen new file with the old name. Use this
         * for writing out a file in multiple pieces
         * at specified checkpoints (e.g. every n hours).
         * @param $newname mixed File name. May be a string or an array with one element
         */
        function closeRenameAndReopen( $newname ) {
                return;
        }

        /**
         * Close the old file, and move it to a specified name.
         * Use this for the last piece of a file written out
         * at specified checkpoints (e.g. every n hours).
         * @param $newname mixed File name. May be a string or an array with one element
         * @param $open bool If true, a new file with the old filename will be opened again for writing (default: false)
         */
        function closeAndRename( $newname, $open = false ) {
                return;
        }

        /**
         * Returns the name of the file or files which are
         * being written to, if there are any.
         * @return null
         */
        function getFilenames() {
                return NULL;
        }
}

/**
 * Stream outputter to send data to a file.
 * @ingroup Dump
 */
class DumpFileOutput extends DumpOutput {
        protected $handle = false, $filename;

        /**
         * @param $file
         */
        function __construct( $file ) {
                $this->handle = fopen( $file, "wt" );
                $this->filename = $file;
        }

        /**
         * @param $string string
         */
        function writeCloseStream( $string ) {
                parent::writeCloseStream( $string );
                if ( $this->handle ) {
                        fclose( $this->handle );
                        $this->handle = false;
                }
        }

        /**
         * @param $string string
         */
        function write( $string ) {
                fputs( $this->handle, $string );
        }

        /**
         * @param $newname
         */
        function closeRenameAndReopen( $newname ) {
                $this->closeAndRename( $newname, true );
        }

        /**
         * @param $newname
         * @throws MWException
         */
        function renameOrException( $newname ) {
                        if (! rename( $this->filename, $newname ) ) {
                                throw new MWException( __METHOD__ . ": rename of file {$this->filename} to $newname failed\n" );
                        }
        }

        /**
         * @param $newname array
         * @return mixed
         * @throws MWException
         */
        function checkRenameArgCount( $newname ) {
                if ( is_array( $newname ) ) {
                        if ( count( $newname ) > 1 ) {
                                throw new MWException( __METHOD__ . ": passed multiple arguments for rename of single file\n" );
                        } else {
                                $newname = $newname[0];
                        }
                }
                return $newname;
        }

        /**
         * @param $newname mixed
         * @param $open bool
         */
        function closeAndRename( $newname, $open = false ) {
                $newname = $this->checkRenameArgCount( $newname );
                if ( $newname ) {
                        if ( $this->handle ) {
                                fclose( $this->handle );
                                $this->handle = false;
                        }
                        $this->renameOrException( $newname );
                        if ( $open ) {
                                $this->handle = fopen( $this->filename, "wt" );
                        }
                }
        }

        /**
         * @return string|null
         */
        function getFilenames() {
                return $this->filename;
        }
}

/**
 * Stream outputter to send data to a file via some filter program.
 * Even if compression is available in a library, using a separate
 * program can allow us to make use of a multi-processor system.
 * @ingroup Dump
 */
class DumpPipeOutput extends DumpFileOutput {
        protected $command, $filename;
        protected $procOpenResource = false;

        /**
         * @param $command
         * @param $file null
         */
        function __construct( $command, $file = null ) {
                if ( !is_null( $file ) ) {
                        $command .=  " > " . wfEscapeShellArg( $file );
                }

                $this->startCommand( $command );
                $this->command = $command;
                $this->filename = $file;
        }

        /**
         * @param $string string
         */
        function writeCloseStream( $string ) {
                parent::writeCloseStream( $string );
                if ( $this->procOpenResource ) {
                        proc_close( $this->procOpenResource );
                        $this->procOpenResource = false;
                }
        }

        /**
         * @param $command
         */
        function startCommand( $command ) {
                $spec = array(
                        0 => array( "pipe", "r" ),
                );
                $pipes = array();
                $this->procOpenResource = proc_open( $command, $spec, $pipes );
                $this->handle = $pipes[0];
        }

        /**
         * @param mixed $newname
         */
        function closeRenameAndReopen( $newname ) {
                $this->closeAndRename( $newname, true );
        }

        /**
         * @param $newname mixed
         * @param $open bool
         */
        function closeAndRename( $newname, $open = false ) {
                $newname = $this->checkRenameArgCount( $newname );
                if ( $newname ) {
                        if ( $this->handle ) {
                                fclose( $this->handle );
                                $this->handle = false;
                        }
                        if ( $this->procOpenResource ) {
                                proc_close( $this->procOpenResource );
                                $this->procOpenResource = false;
                        }
                        $this->renameOrException( $newname );
                        if ( $open ) {
                                $command = $this->command;
                                $command .=  " > " . wfEscapeShellArg( $this->filename );
                                $this->startCommand( $command );
                        }
                }
        }

}

/**
 * Sends dump output via the gzip compressor.
 * @ingroup Dump
 */
class DumpGZipOutput extends DumpPipeOutput {

        /**
         * @param $file string
         */
        function __construct( $file ) {
                parent::__construct( "gzip", $file );
        }
}

/**
 * Sends dump output via the bgzip2 compressor.
 * @ingroup Dump
 */
class DumpBZip2Output extends DumpPipeOutput {

        /**
         * @param $file string
         */
        function __construct( $file ) {
                parent::__construct( "bzip2", $file );
        }
}

/**
 * Sends dump output via the p7zip compressor.
 * @ingroup Dump
 */
class Dump7ZipOutput extends DumpPipeOutput {

        /**
         * @param $file string
         */
        function __construct( $file ) {
                $command = $this->setup7zCommand( $file );
                parent::__construct( $command );
                $this->filename = $file;
        }

        /**
         * @param $file string
         * @return string
         */
        function setup7zCommand( $file ) {
                $command = "7za a -bd -si " . wfEscapeShellArg( $file );
                // Suppress annoying useless crap from p7zip
                // Unfortunately this could suppress real error messages too
                $command .= ' >' . wfGetNull() . ' 2>&1';
                return( $command );
        }

        /**
         * @param $newname string
         * @param $open bool
         */
        function closeAndRename( $newname, $open = false ) {
                $newname = $this->checkRenameArgCount( $newname );
                if ( $newname ) {
                        fclose( $this->handle );
                        proc_close( $this->procOpenResource );
                        $this->renameOrException( $newname );
                        if ( $open ) {
                                $command = $this->setup7zCommand( $this->filename );
                                $this->startCommand( $command );
                        }
                }
        }
}

/**
 * Dump output filter class.
 * This just does output filtering and streaming; XML formatting is done
 * higher up, so be careful in what you do.
 * @ingroup Dump
 */
class DumpFilter {

        /**
         * @var DumpOutput
         * FIXME will need to be made protected whenever legacy code
         * is updated.
         */
        public $sink;

        /**
         * @var bool
         */
        protected $sendingThisPage;

        /**
         * @param $sink DumpOutput
         */
        function __construct( &$sink ) {
                $this->sink =& $sink;
        }

        /**
         * @param $string string
         */
        function writeOpenStream( $string ) {
                $this->sink->writeOpenStream( $string );
        }

        /**
         * @param $string string
         */
        function writeCloseStream( $string ) {
                $this->sink->writeCloseStream( $string );
        }

        /**
         * @param $page
         * @param $string string
         */
        function writeOpenPage( $page, $string ) {
                $this->sendingThisPage = $this->pass( $page, $string );
                if ( $this->sendingThisPage ) {
                        $this->sink->writeOpenPage( $page, $string );
                }
        }

        /**
         * @param $string string
         */
        function writeClosePage( $string ) {
                if ( $this->sendingThisPage ) {
                        $this->sink->writeClosePage( $string );
                        $this->sendingThisPage = false;
                }
        }

        /**
         * @param $rev
         * @param $string string
         */
        function writeRevision( $rev, $string ) {
                if ( $this->sendingThisPage ) {
                        $this->sink->writeRevision( $rev, $string );
                }
        }

        /**
         * @param $rev
         * @param $string string
         */
        function writeLogItem( $rev, $string ) {
                $this->sink->writeRevision( $rev, $string );
        }

        /**
         * @param $newname string
         */
        function closeRenameAndReopen( $newname ) {
                $this->sink->closeRenameAndReopen( $newname );
        }

        /**
         * @param $newname string
         * @param $open bool
         */
        function closeAndRename( $newname, $open = false ) {
                $this->sink->closeAndRename( $newname, $open );
        }

        /**
         * @return array
         */
        function getFilenames() {
                return $this->sink->getFilenames();
        }

        /**
         * Override for page-based filter types.
         * @param $page
         * @return bool
         */
        function pass( $page ) {
                return true;
        }
}

/**
 * Simple dump output filter to exclude all talk pages.
 * @ingroup Dump
 */
class DumpNotalkFilter extends DumpFilter {

        /**
         * @param $page
         * @return bool
         */
        function pass( $page ) {
                return !MWNamespace::isTalk( $page->page_namespace );
        }
}

/**
 * Dump output filter to include or exclude pages in a given set of namespaces.
 * @ingroup Dump
 */
class DumpNamespaceFilter extends DumpFilter {
        var $invert = false;
        var $namespaces = array();

        /**
         * @param $sink DumpOutput
         * @param $param
         */
        function __construct( &$sink, $param ) {
                parent::__construct( $sink );

                $constants = array(
                        "NS_MAIN"           => NS_MAIN,
                        "NS_TALK"           => NS_TALK,
                        "NS_USER"           => NS_USER,
                        "NS_USER_TALK"      => NS_USER_TALK,
                        "NS_PROJECT"        => NS_PROJECT,
                        "NS_PROJECT_TALK"   => NS_PROJECT_TALK,
                        "NS_FILE"           => NS_FILE,
                        "NS_FILE_TALK"      => NS_FILE_TALK,
                        "NS_IMAGE"          => NS_IMAGE,  // NS_IMAGE is an alias for NS_FILE
                        "NS_IMAGE_TALK"     => NS_IMAGE_TALK,
                        "NS_MEDIAWIKI"      => NS_MEDIAWIKI,
                        "NS_MEDIAWIKI_TALK" => NS_MEDIAWIKI_TALK,
                        "NS_TEMPLATE"       => NS_TEMPLATE,
                        "NS_TEMPLATE_TALK"  => NS_TEMPLATE_TALK,
                        "NS_HELP"           => NS_HELP,
                        "NS_HELP_TALK"      => NS_HELP_TALK,
                        "NS_CATEGORY"       => NS_CATEGORY,
                        "NS_CATEGORY_TALK"  => NS_CATEGORY_TALK );

                if ( $param { 0 } == '!' ) {
                        $this->invert = true;
                        $param = substr( $param, 1 );
                }

                foreach ( explode( ',', $param ) as $key ) {
                        $key = trim( $key );
                        if ( isset( $constants[$key] ) ) {
                                $ns = $constants[$key];
                                $this->namespaces[$ns] = true;
                        } elseif ( is_numeric( $key ) ) {
                                $ns = intval( $key );
                                $this->namespaces[$ns] = true;
                        } else {
                                throw new MWException( "Unrecognized namespace key '$key'\n" );
                        }
                }
        }

        /**
         * @param $page
         * @return bool
         */
        function pass( $page ) {
                $match = isset( $this->namespaces[$page->page_namespace] );
                return $this->invert xor $match;
        }
}


/**
 * Dump output filter to include only the last revision in each page sequence.
 * @ingroup Dump
 */
class DumpLatestFilter extends DumpFilter {
        var $page, $pageString, $rev, $revString;

        /**
         * @param $page
         * @param $string string
         */
        function writeOpenPage( $page, $string ) {
                $this->page = $page;
                $this->pageString = $string;
        }

        /**
         * @param $string string
         */
        function writeClosePage( $string ) {
                if ( $this->rev ) {
                        $this->sink->writeOpenPage( $this->page, $this->pageString );
                        $this->sink->writeRevision( $this->rev, $this->revString );
                        $this->sink->writeClosePage( $string );
                }
                $this->rev = null;
                $this->revString = null;
                $this->page = null;
                $this->pageString = null;
        }

        /**
         * @param $rev
         * @param $string string
         */
        function writeRevision( $rev, $string ) {
                if ( $rev->rev_id == $this->page->page_latest ) {
                        $this->rev = $rev;
                        $this->revString = $string;
                }
        }
}

/**
 * Base class for output stream; prints to stdout or buffer or whereever.
 * @ingroup Dump
 */
class DumpMultiWriter {

        /**
         * @param $sinks
         */
        function __construct( $sinks ) {
                $this->sinks = $sinks;
                $this->count = count( $sinks );
        }

        /**
         * @param $string string
         */
        function writeOpenStream( $string ) {
                for ( $i = 0; $i < $this->count; $i++ ) {
                        $this->sinks[$i]->writeOpenStream( $string );
                }
        }

        /**
         * @param $string string
         */
        function writeCloseStream( $string ) {
                for ( $i = 0; $i < $this->count; $i++ ) {
                        $this->sinks[$i]->writeCloseStream( $string );
                }
        }

        /**
         * @param $page
         * @param $string string
         */
        function writeOpenPage( $page, $string ) {
                for ( $i = 0; $i < $this->count; $i++ ) {
                        $this->sinks[$i]->writeOpenPage( $page, $string );
                }
        }

        /**
         * @param $string
         */
        function writeClosePage( $string ) {
                for ( $i = 0; $i < $this->count; $i++ ) {
                        $this->sinks[$i]->writeClosePage( $string );
                }
        }

        /**
         * @param $rev
         * @param $string
         */
        function writeRevision( $rev, $string ) {
                for ( $i = 0; $i < $this->count; $i++ ) {
                        $this->sinks[$i]->writeRevision( $rev, $string );
                }
        }

        /**
         * @param $newnames
         */
        function closeRenameAndReopen( $newnames ) {
                $this->closeAndRename( $newnames, true );
        }

        /**
         * @param $newnames array
         * @param bool $open
         */
        function closeAndRename( $newnames, $open = false ) {
                for ( $i = 0; $i < $this->count; $i++ ) {
                        $this->sinks[$i]->closeAndRename( $newnames[$i], $open );
                }
        }

        /**
         * @return array
         */
        function getFilenames() {
                $filenames = array();
                for ( $i = 0; $i < $this->count; $i++ ) {
                        $filenames[] =  $this->sinks[$i]->getFilenames();
                }
                return $filenames;
        }

}

/**
 * @param $string string
 * @return string
 */
function xmlsafe( $string ) {
        wfProfileIn( __FUNCTION__ );

        /**
         * The page may contain old data which has not been properly normalized.
         * Invalid UTF-8 sequences or forbidden control characters will make our
         * XML output invalid, so be sure to strip them out.
         */
        $string = UtfNormal::cleanUp( $string );

        $string = htmlspecialchars( $string );
        wfProfileOut( __FUNCTION__ );
        return $string;
}