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<?php
/**
* Helper class for the --prefetch option of dumpTextPass.php
*
* Copyright © 2005 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
* @ingroup Maintenance
*/
/**
* Readahead helper for making large MediaWiki data dumps;
* reads in a previous XML dump to sequentially prefetch text
* records already normalized and decompressed.
*
* This can save load on the external database servers, hopefully.
*
* Assumes that dumps will be recorded in the canonical order:
* - ascending by page_id
* - ascending by rev_id within each page
* - text contents are immutable and should not change once
* recorded, so the previous dump is a reliable source
*
* @ingroup Maintenance
*/
class BaseDump {
var $reader = null;
var $atEnd = false;
var $atPageEnd = false;
var $lastPage = 0;
var $lastRev = 0;
var $infiles = null;
function BaseDump( $infile ) {
$this->infiles = explode( ';', $infile );
$this->reader = new XMLReader();
$infile = array_shift( $this->infiles );
if ( defined( 'LIBXML_PARSEHUGE' ) ) {
$this->reader->open( $infile, null, LIBXML_PARSEHUGE );
}
else {
$this->reader->open( $infile );
}
}
/**
* Attempts to fetch the text of a particular page revision
* from the dump stream. May return null if the page is
* unavailable.
*
* @param $page Integer: ID number of page to read
* @param $rev Integer: ID number of revision to read
* @return string or null
*/
function prefetch( $page, $rev ) {
$page = intval( $page );
$rev = intval( $rev );
while ( $this->lastPage < $page && !$this->atEnd ) {
$this->debug( "BaseDump::prefetch at page $this->lastPage, looking for $page" );
$this->nextPage();
}
if ( $this->lastPage > $page || $this->atEnd ) {
$this->debug( "BaseDump::prefetch already past page $page looking for rev $rev [$this->lastPage, $this->lastRev]" );
return null;
}
while ( $this->lastRev < $rev && !$this->atEnd && !$this->atPageEnd ) {
$this->debug( "BaseDump::prefetch at page $this->lastPage, rev $this->lastRev, looking for $page, $rev" );
$this->nextRev();
}
if ( $this->lastRev == $rev && !$this->atEnd ) {
$this->debug( "BaseDump::prefetch hit on $page, $rev [$this->lastPage, $this->lastRev]" );
return $this->nextText();
} else {
$this->debug( "BaseDump::prefetch already past rev $rev on page $page [$this->lastPage, $this->lastRev]" );
return null;
}
}
function debug( $str ) {
wfDebug( $str . "\n" );
// global $dumper;
// $dumper->progress( $str );
}
/**
* @access private
*/
function nextPage() {
if ( $this->skipTo( 'page', 'mediawiki' ) ) {
if ( $this->skipTo( 'id' ) ) {
$this->lastPage = intval( $this->nodeContents() );
$this->lastRev = 0;
$this->atPageEnd = false;
}
} else {
$this->close();
if ( count( $this->infiles ) ) {
$infile = array_shift( $this->infiles );
$this->reader->open( $infile );
$this->atEnd = false;
}
}
}
/**
* @access private
*/
function nextRev() {
if ( $this->skipTo( 'revision' ) ) {
if ( $this->skipTo( 'id' ) ) {
$this->lastRev = intval( $this->nodeContents() );
}
} else {
$this->atPageEnd = true;
}
}
/**
* @access private
* @return string
*/
function nextText() {
$this->skipTo( 'text' );
return strval( $this->nodeContents() );
}
/**
* @access private
* @param $name string
* @param $parent string
* @return bool|null
*/
function skipTo( $name, $parent = 'page' ) {
if ( $this->atEnd ) {
return false;
}
while ( $this->reader->read() ) {
if ( $this->reader->nodeType == XMLReader::ELEMENT &&
$this->reader->name == $name ) {
return true;
}
if ( $this->reader->nodeType == XMLReader::END_ELEMENT &&
$this->reader->name == $parent ) {
$this->debug( "BaseDump::skipTo found </$parent> searching for <$name>" );
return false;
}
}
return $this->close();
}
/**
* Shouldn't something like this be built-in to XMLReader?
* Fetches text contents of the current element, assuming
* no sub-elements or such scary things.
*
* @return String
* @access private
*/
function nodeContents() {
if ( $this->atEnd ) {
return null;
}
if ( $this->reader->isEmptyElement ) {
return "";
}
$buffer = "";
while ( $this->reader->read() ) {
switch ( $this->reader->nodeType ) {
case XMLReader::TEXT:
// case XMLReader::WHITESPACE:
case XMLReader::SIGNIFICANT_WHITESPACE:
$buffer .= $this->reader->value;
break;
case XMLReader::END_ELEMENT:
return $buffer;
}
}
return $this->close();
}
/**
* @access private
* @return null
*/
function close() {
$this->reader->close();
$this->atEnd = true;
return null;
}
}
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