OutputHandler.php

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<?php
function wfOutputHandler( $s ) {
    global $wgDisableOutputCompression, $wgValidateAllHtml, $wgMangleFlashPolicy;
    if ( $wgMangleFlashPolicy ) {
        $s = wfMangleFlashPolicy( $s );
    }
    if ( $wgValidateAllHtml ) {
        $headers = headers_list();
        $isHTML = false;
        foreach ( $headers as $header ) {
            $parts = explode( ':', $header, 2 );
            if ( count( $parts ) !== 2 ) {
                continue;
            }
            $name = strtolower( trim( $parts[0] ) );
            $value = trim( $parts[1] );
            if ( $name == 'content-type' && ( strpos( $value, 'text/html' ) === 0
                || strpos( $value, 'application/xhtml+xml' ) === 0 )
            ) {
                $isHTML = true;
                break;
            }
        }
        if ( $isHTML ) {
            $s = wfHtmlValidationHandler( $s );
        }
    }
    if ( !$wgDisableOutputCompression && !ini_get( 'zlib.output_compression' ) ) {
        if ( !defined( 'MW_NO_OUTPUT_COMPRESSION' ) ) {
            $s = wfGzipHandler( $s );
        }
        if ( !ini_get( 'output_handler' ) ) {
            wfDoContentLength( strlen( $s ) );
        }
    }
    return $s;
}

function wfRequestExtension() {
    if ( isset( $_SERVER['REQUEST_URI'] ) ) {
        // Strip the query string...
        list( $path ) = explode( '?', $_SERVER['REQUEST_URI'], 2 );
    } elseif ( isset( $_SERVER['SCRIPT_NAME'] ) ) {
        // Probably IIS. QUERY_STRING appears separately.
        $path = $_SERVER['SCRIPT_NAME'];
    } else {
        // Can't get the path from the server? :(
        return '';
    }

    $period = strrpos( $path, '.' );
    if ( $period !== false ) {
        return strtolower( substr( $path, $period ) );
    }
    return '';
}

function wfGzipHandler( $s ) {
    if ( !function_exists( 'gzencode' ) ) {
        wfDebug( __FUNCTION__ . "() skipping compression (gzencode unavailable)\n" );
        return $s;
    }
    if ( headers_sent() ) {
        wfDebug( __FUNCTION__ . "() skipping compression (headers already sent)\n" );
        return $s;
    }

    $ext = wfRequestExtension();
    if ( $ext == '.gz' || $ext == '.tgz' ) {
        // Don't do gzip compression if the URL path ends in .gz or .tgz
        // This confuses Safari and triggers a download of the page,
        // even though it's pretty clearly labeled as viewable HTML.
        // Bad Safari! Bad!
        return $s;
    }

    if ( wfClientAcceptsGzip() ) {
        wfDebug( __FUNCTION__ . "() is compressing output\n" );
        header( 'Content-Encoding: gzip' );
        $s = gzencode( $s, 6 );
    }

    // Set vary header if it hasn't been set already
    $headers = headers_list();
    $foundVary = false;
    foreach ( $headers as $header ) {
        $headerName = strtolower( substr( $header, 0, 5 ) );
        if ( $headerName == 'vary:' ) {
            $foundVary = true;
            break;
        }
    }
    if ( !$foundVary ) {
        header( 'Vary: Accept-Encoding' );
        global $wgUseKeyHeader;
        if ( $wgUseKeyHeader ) {
            header( 'Key: Accept-Encoding;match=gzip' );
        }
    }
    return $s;
}

function wfMangleFlashPolicy( $s ) {
    # Avoid weird excessive memory usage in PCRE on big articles
    if ( preg_match( '/<\s*cross-domain-policy(?=\s|>)/i', $s ) ) {
        return preg_replace( '/<(\s*)(cross-domain-policy(?=\s|>))/i', '<$1NOT-$2', $s );
    } else {
        return $s;
    }
}

function wfDoContentLength( $length ) {
    if ( !headers_sent()
        && isset( $_SERVER['SERVER_PROTOCOL'] )
        && $_SERVER['SERVER_PROTOCOL'] == 'HTTP/1.0'
    ) {
        header( "Content-Length: $length" );
    }
}

function wfHtmlValidationHandler( $s ) {

    $errors = '';
    if ( MWTidy::checkErrors( $s, $errors ) ) {
        return $s;
    }

    header( 'Cache-Control: no-cache' );

    $out = Html::element( 'h1', null, 'HTML validation error' );
    $out .= Html::openElement( 'ul' );

    $error = strtok( $errors, "\n" );
    $badLines = [];
    while ( $error !== false ) {
        if ( preg_match( '/^line (\d+)/', $error, $m ) ) {
            $lineNum = intval( $m[1] );
            $badLines[$lineNum] = true;
            $out .= Html::rawElement( 'li', null,
                Html::element( 'a', [ 'href' => "#line-{$lineNum}" ], $error ) ) . "\n";
        }
        $error = strtok( "\n" );
    }

    $out .= Html::closeElement( 'ul' );
    $out .= Html::element( 'pre', null, $errors );
    $out .= Html::openElement( 'ol' ) . "\n";
    $line = strtok( $s, "\n" );
    $i = 1;
    while ( $line !== false ) {
        $attrs = [];
        if ( isset( $badLines[$i] ) ) {
            $attrs['class'] = 'highlight';
            $attrs['id'] = "line-$i";
        }
        $out .= Html::element( 'li', $attrs, $line ) . "\n";
        $line = strtok( "\n" );
        $i++;
    }
    $out .= Html::closeElement( 'ol' );

    $style = <<<CSS
.highlight { background-color: #ffc }
li { white-space: pre }
CSS;

    $out = Html::htmlHeader( [ 'lang' => 'en', 'dir' => 'ltr' ] ) .
        Html::rawElement( 'head', null,
            Html::element( 'title', null, 'HTML validation error' ) .
            Html::inlineStyle( $style ) ) .
        Html::rawElement( 'body', null, $out ) .
        Html::closeElement( 'html' );

    return $out;
}