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+<?php
+/**
+ * Efficient paging for SQL queries.
+ *
+ * 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 Pager
+ */
+
+/**
+ * IndexPager is an efficient pager which uses a (roughly unique) index in the
+ * data set to implement paging, rather than a "LIMIT offset,limit" clause.
+ * In MySQL, such a limit/offset clause requires counting through the
+ * specified number of offset rows to find the desired data, which can be
+ * expensive for large offsets.
+ *
+ * ReverseChronologicalPager is a child class of the abstract IndexPager, and
+ * contains some formatting and display code which is specific to the use of
+ * timestamps as indexes. Here is a synopsis of its operation:
+ *
+ * * The query is specified by the offset, limit and direction (dir)
+ * parameters, in addition to any subclass-specific parameters.
+ * * The offset is the non-inclusive start of the DB query. A row with an
+ * index value equal to the offset will never be shown.
+ * * The query may either be done backwards, where the rows are returned by
+ * the database in the opposite order to which they are displayed to the
+ * user, or forwards. This is specified by the "dir" parameter, dir=prev
+ * means backwards, anything else means forwards. The offset value
+ * specifies the start of the database result set, which may be either
+ * the start or end of the displayed data set. This allows "previous"
+ * links to be implemented without knowledge of the index value at the
+ * start of the previous page.
+ * * An additional row beyond the user-specified limit is always requested.
+ * This allows us to tell whether we should display a "next" link in the
+ * case of forwards mode, or a "previous" link in the case of backwards
+ * mode. Determining whether to display the other link (the one for the
+ * page before the start of the database result set) can be done
+ * heuristically by examining the offset.
+ *
+ * * An empty offset indicates that the offset condition should be omitted
+ * from the query. This naturally produces either the first page or the
+ * last page depending on the dir parameter.
+ *
+ * Subclassing the pager to implement concrete functionality should be fairly
+ * simple, please see the examples in HistoryAction.php and
+ * SpecialBlockList.php. You just need to override formatRow(),
+ * getQueryInfo() and getIndexField(). Don't forget to call the parent
+ * constructor if you override it.
+ *
+ * @ingroup Pager
+ */
+abstract class IndexPager extends ContextSource implements Pager {
+ /**
+ * Constants for the $mDefaultDirection field.
+ *
+ * These are boolean for historical reasons and should stay boolean for backwards-compatibility.
+ */
+ const DIR_ASCENDING = false;
+ const DIR_DESCENDING = true;
+
+ public $mRequest;
+ public $mLimitsShown = array( 20, 50, 100, 250, 500 );
+ public $mDefaultLimit = 50;
+ public $mOffset, $mLimit;
+ public $mQueryDone = false;
+ public $mDb;
+ public $mPastTheEndRow;
+
+ /**
+ * The index to actually be used for ordering. This is a single column,
+ * for one ordering, even if multiple orderings are supported.
+ */
+ protected $mIndexField;
+ /**
+ * An array of secondary columns to order by. These fields are not part of the offset.
+ * This is a column list for one ordering, even if multiple orderings are supported.
+ */
+ protected $mExtraSortFields;
+ /** For pages that support multiple types of ordering, which one to use.
+ */
+ protected $mOrderType;
+ /**
+ * $mDefaultDirection gives the direction to use when sorting results:
+ * DIR_ASCENDING or DIR_DESCENDING. If $mIsBackwards is set, we
+ * start from the opposite end, but we still sort the page itself according
+ * to $mDefaultDirection. E.g., if $mDefaultDirection is false but we're
+ * going backwards, we'll display the last page of results, but the last
+ * result will be at the bottom, not the top.
+ *
+ * Like $mIndexField, $mDefaultDirection will be a single value even if the
+ * class supports multiple default directions for different order types.
+ */
+ public $mDefaultDirection;
+ public $mIsBackwards;
+
+ /** True if the current result set is the first one */
+ public $mIsFirst;
+ public $mIsLast;
+
+ protected $mLastShown, $mFirstShown, $mPastTheEndIndex, $mDefaultQuery, $mNavigationBar;
+
+ /**
+ * Whether to include the offset in the query
+ */
+ protected $mIncludeOffset = false;
+
+ /**
+ * Result object for the query. Warning: seek before use.
+ *
+ * @var ResultWrapper
+ */
+ public $mResult;
+
+ public function __construct( IContextSource $context = null ) {
+ if ( $context ) {
+ $this->setContext( $context );
+ }
+
+ $this->mRequest = $this->getRequest();
+
+ # NB: the offset is quoted, not validated. It is treated as an
+ # arbitrary string to support the widest variety of index types. Be
+ # careful outputting it into HTML!
+ $this->mOffset = $this->mRequest->getText( 'offset' );
+
+ # Use consistent behavior for the limit options
+ $this->mDefaultLimit = $this->getUser()->getIntOption( 'rclimit' );
+ if ( !$this->mLimit ) {
+ // Don't override if a subclass calls $this->setLimit() in its constructor.
+ list( $this->mLimit, /* $offset */ ) = $this->mRequest->getLimitOffset();
+ }
+
+ $this->mIsBackwards = ( $this->mRequest->getVal( 'dir' ) == 'prev' );
+ # Let the subclass set the DB here; otherwise use a slave DB for the current wiki
+ $this->mDb = $this->mDb ?: wfGetDB( DB_SLAVE );
+
+ $index = $this->getIndexField(); // column to sort on
+ $extraSort = $this->getExtraSortFields(); // extra columns to sort on for query planning
+ $order = $this->mRequest->getVal( 'order' );
+ if ( is_array( $index ) && isset( $index[$order] ) ) {
+ $this->mOrderType = $order;
+ $this->mIndexField = $index[$order];
+ $this->mExtraSortFields = isset( $extraSort[$order] )
+ ? (array)$extraSort[$order]
+ : array();
+ } elseif ( is_array( $index ) ) {
+ # First element is the default
+ reset( $index );
+ list( $this->mOrderType, $this->mIndexField ) = each( $index );
+ $this->mExtraSortFields = isset( $extraSort[$this->mOrderType] )
+ ? (array)$extraSort[$this->mOrderType]
+ : array();
+ } else {
+ # $index is not an array
+ $this->mOrderType = null;
+ $this->mIndexField = $index;
+ $this->mExtraSortFields = (array)$extraSort;
+ }
+
+ if ( !isset( $this->mDefaultDirection ) ) {
+ $dir = $this->getDefaultDirections();
+ $this->mDefaultDirection = is_array( $dir )
+ ? $dir[$this->mOrderType]
+ : $dir;
+ }
+ }
+
+ /**
+ * Get the Database object in use
+ *
+ * @return DatabaseBase
+ */
+ public function getDatabase() {
+ return $this->mDb;
+ }
+
+ /**
+ * Do the query, using information from the object context. This function
+ * has been kept minimal to make it overridable if necessary, to allow for
+ * result sets formed from multiple DB queries.
+ */
+ public function doQuery() {
+ # Use the child class name for profiling
+ $fname = __METHOD__ . ' (' . get_class( $this ) . ')';
+ wfProfileIn( $fname );
+
+ // @todo This should probably compare to DIR_DESCENDING and DIR_ASCENDING constants
+ $descending = ( $this->mIsBackwards == $this->mDefaultDirection );
+ # Plus an extra row so that we can tell the "next" link should be shown
+ $queryLimit = $this->mLimit + 1;
+
+ if ( $this->mOffset == '' ) {
+ $isFirst = true;
+ } else {
+ // If there's an offset, we may or may not be at the first entry.
+ // The only way to tell is to run the query in the opposite
+ // direction see if we get a row.
+ $oldIncludeOffset = $this->mIncludeOffset;
+ $this->mIncludeOffset = !$this->mIncludeOffset;
+ $isFirst = !$this->reallyDoQuery( $this->mOffset, 1, !$descending )->numRows();
+ $this->mIncludeOffset = $oldIncludeOffset;
+ }
+
+ $this->mResult = $this->reallyDoQuery(
+ $this->mOffset,
+ $queryLimit,
+ $descending
+ );
+
+ $this->extractResultInfo( $isFirst, $queryLimit, $this->mResult );
+ $this->mQueryDone = true;
+
+ $this->preprocessResults( $this->mResult );
+ $this->mResult->rewind(); // Paranoia
+
+ wfProfileOut( $fname );
+ }
+
+ /**
+ * @return ResultWrapper The result wrapper.
+ */
+ function getResult() {
+ return $this->mResult;
+ }
+
+ /**
+ * Set the offset from an other source than the request
+ *
+ * @param int|string $offset
+ */
+ function setOffset( $offset ) {
+ $this->mOffset = $offset;
+ }
+
+ /**
+ * Set the limit from an other source than the request
+ *
+ * Verifies limit is between 1 and 5000
+ *
+ * @param int|string $limit
+ */
+ function setLimit( $limit ) {
+ $limit = (int)$limit;
+ // WebRequest::getLimitOffset() puts a cap of 5000, so do same here.
+ if ( $limit > 5000 ) {
+ $limit = 5000;
+ }
+ if ( $limit > 0 ) {
+ $this->mLimit = $limit;
+ }
+ }
+
+ /**
+ * Get the current limit
+ *
+ * @return int
+ */
+ function getLimit() {
+ return $this->mLimit;
+ }
+
+ /**
+ * Set whether a row matching exactly the offset should be also included
+ * in the result or not. By default this is not the case, but when the
+ * offset is user-supplied this might be wanted.
+ *
+ * @param bool $include
+ */
+ public function setIncludeOffset( $include ) {
+ $this->mIncludeOffset = $include;
+ }
+
+ /**
+ * Extract some useful data from the result object for use by
+ * the navigation bar, put it into $this
+ *
+ * @param bool $isFirst False if there are rows before those fetched (i.e.
+ * if a "previous" link would make sense)
+ * @param int $limit Exact query limit
+ * @param ResultWrapper $res
+ */
+ function extractResultInfo( $isFirst, $limit, ResultWrapper $res ) {
+ $numRows = $res->numRows();
+ if ( $numRows ) {
+ # Remove any table prefix from index field
+ $parts = explode( '.', $this->mIndexField );
+ $indexColumn = end( $parts );
+
+ $row = $res->fetchRow();
+ $firstIndex = $row[$indexColumn];
+
+ # Discard the extra result row if there is one
+ if ( $numRows > $this->mLimit && $numRows > 1 ) {
+ $res->seek( $numRows - 1 );
+ $this->mPastTheEndRow = $res->fetchObject();
+ $this->mPastTheEndIndex = $this->mPastTheEndRow->$indexColumn;
+ $res->seek( $numRows - 2 );
+ $row = $res->fetchRow();
+ $lastIndex = $row[$indexColumn];
+ } else {
+ $this->mPastTheEndRow = null;
+ # Setting indexes to an empty string means that they will be
+ # omitted if they would otherwise appear in URLs. It just so
+ # happens that this is the right thing to do in the standard
+ # UI, in all the relevant cases.
+ $this->mPastTheEndIndex = '';
+ $res->seek( $numRows - 1 );
+ $row = $res->fetchRow();
+ $lastIndex = $row[$indexColumn];
+ }
+ } else {
+ $firstIndex = '';
+ $lastIndex = '';
+ $this->mPastTheEndRow = null;
+ $this->mPastTheEndIndex = '';
+ }
+
+ if ( $this->mIsBackwards ) {
+ $this->mIsFirst = ( $numRows < $limit );
+ $this->mIsLast = $isFirst;
+ $this->mLastShown = $firstIndex;
+ $this->mFirstShown = $lastIndex;
+ } else {
+ $this->mIsFirst = $isFirst;
+ $this->mIsLast = ( $numRows < $limit );
+ $this->mLastShown = $lastIndex;
+ $this->mFirstShown = $firstIndex;
+ }
+ }
+
+ /**
+ * Get some text to go in brackets in the "function name" part of the SQL comment
+ *
+ * @return string
+ */
+ function getSqlComment() {
+ return get_class( $this );
+ }
+
+ /**
+ * Do a query with specified parameters, rather than using the object
+ * context
+ *
+ * @param string $offset Index offset, inclusive
+ * @param int $limit Exact query limit
+ * @param bool $descending Query direction, false for ascending, true for descending
+ * @return ResultWrapper
+ */
+ public function reallyDoQuery( $offset, $limit, $descending ) {
+ list( $tables, $fields, $conds, $fname, $options, $join_conds ) =
+ $this->buildQueryInfo( $offset, $limit, $descending );
+
+ return $this->mDb->select( $tables, $fields, $conds, $fname, $options, $join_conds );
+ }
+
+ /**
+ * Build variables to use by the database wrapper.
+ *
+ * @param string $offset Index offset, inclusive
+ * @param int $limit Exact query limit
+ * @param bool $descending Query direction, false for ascending, true for descending
+ * @return array
+ */
+ protected function buildQueryInfo( $offset, $limit, $descending ) {
+ $fname = __METHOD__ . ' (' . $this->getSqlComment() . ')';
+ $info = $this->getQueryInfo();
+ $tables = $info['tables'];
+ $fields = $info['fields'];
+ $conds = isset( $info['conds'] ) ? $info['conds'] : array();
+ $options = isset( $info['options'] ) ? $info['options'] : array();
+ $join_conds = isset( $info['join_conds'] ) ? $info['join_conds'] : array();
+ $sortColumns = array_merge( array( $this->mIndexField ), $this->mExtraSortFields );
+ if ( $descending ) {
+ $options['ORDER BY'] = $sortColumns;
+ $operator = $this->mIncludeOffset ? '>=' : '>';
+ } else {
+ $orderBy = array();
+ foreach ( $sortColumns as $col ) {
+ $orderBy[] = $col . ' DESC';
+ }
+ $options['ORDER BY'] = $orderBy;
+ $operator = $this->mIncludeOffset ? '<=' : '<';
+ }
+ if ( $offset != '' ) {
+ $conds[] = $this->mIndexField . $operator . $this->mDb->addQuotes( $offset );
+ }
+ $options['LIMIT'] = intval( $limit );
+ return array( $tables, $fields, $conds, $fname, $options, $join_conds );
+ }
+
+ /**
+ * Pre-process results; useful for performing batch existence checks, etc.
+ *
+ * @param ResultWrapper $result
+ */
+ protected function preprocessResults( $result ) {
+ }
+
+ /**
+ * Get the formatted result list. Calls getStartBody(), formatRow() and
+ * getEndBody(), concatenates the results and returns them.
+ *
+ * @return string
+ */
+ public function getBody() {
+ if ( !$this->mQueryDone ) {
+ $this->doQuery();
+ }
+
+ if ( $this->mResult->numRows() ) {
+ # Do any special query batches before display
+ $this->doBatchLookups();
+ }
+
+ # Don't use any extra rows returned by the query
+ $numRows = min( $this->mResult->numRows(), $this->mLimit );
+
+ $s = $this->getStartBody();
+ if ( $numRows ) {
+ if ( $this->mIsBackwards ) {
+ for ( $i = $numRows - 1; $i >= 0; $i-- ) {
+ $this->mResult->seek( $i );
+ $row = $this->mResult->fetchObject();
+ $s .= $this->formatRow( $row );
+ }
+ } else {
+ $this->mResult->seek( 0 );
+ for ( $i = 0; $i < $numRows; $i++ ) {
+ $row = $this->mResult->fetchObject();
+ $s .= $this->formatRow( $row );
+ }
+ }
+ } else {
+ $s .= $this->getEmptyBody();
+ }
+ $s .= $this->getEndBody();
+ return $s;
+ }
+
+ /**
+ * Make a self-link
+ *
+ * @param string $text Text displayed on the link
+ * @param array $query Associative array of parameter to be in the query string
+ * @param string $type Link type used to create additional attributes, like "rel", "class" or
+ * "title". Valid values (non-exhaustive list): 'first', 'last', 'prev', 'next', 'asc', 'desc'.
+ * @return string HTML fragment
+ */
+ function makeLink( $text, array $query = null, $type = null ) {
+ if ( $query === null ) {
+ return $text;
+ }
+
+ $attrs = array();
+ if ( in_array( $type, array( 'prev', 'next' ) ) ) {
+ $attrs['rel'] = $type;
+ }
+
+ if ( in_array( $type, array( 'asc', 'desc' ) ) ) {
+ $attrs['title'] = wfMessage( $type == 'asc' ? 'sort-ascending' : 'sort-descending' )->text();
+ }
+
+ if ( $type ) {
+ $attrs['class'] = "mw-{$type}link";
+ }
+
+
+ return Linker::linkKnown(
+ $this->getTitle(),
+ $text,
+ $attrs,
+ $query + $this->getDefaultQuery()
+ );
+ }
+
+ /**
+ * Called from getBody(), before getStartBody() is called and
+ * after doQuery() was called. This will be called only if there
+ * are rows in the result set.
+ *
+ * @return void
+ */
+ protected function doBatchLookups() {
+ }
+
+ /**
+ * Hook into getBody(), allows text to be inserted at the start. This
+ * will be called even if there are no rows in the result set.
+ *
+ * @return string
+ */
+ protected function getStartBody() {
+ return '';
+ }
+
+ /**
+ * Hook into getBody() for the end of the list
+ *
+ * @return string
+ */
+ protected function getEndBody() {
+ return '';
+ }
+
+ /**
+ * Hook into getBody(), for the bit between the start and the
+ * end when there are no rows
+ *
+ * @return string
+ */
+ protected function getEmptyBody() {
+ return '';
+ }
+
+ /**
+ * Get an array of query parameters that should be put into self-links.
+ * By default, all parameters passed in the URL are used, except for a
+ * short blacklist.
+ *
+ * @return array Associative array
+ */
+ function getDefaultQuery() {
+ if ( !isset( $this->mDefaultQuery ) ) {
+ $this->mDefaultQuery = $this->getRequest()->getQueryValues();
+ unset( $this->mDefaultQuery['title'] );
+ unset( $this->mDefaultQuery['dir'] );
+ unset( $this->mDefaultQuery['offset'] );
+ unset( $this->mDefaultQuery['limit'] );
+ unset( $this->mDefaultQuery['order'] );
+ unset( $this->mDefaultQuery['month'] );
+ unset( $this->mDefaultQuery['year'] );
+ }
+ return $this->mDefaultQuery;
+ }
+
+ /**
+ * Get the number of rows in the result set
+ *
+ * @return int
+ */
+ function getNumRows() {
+ if ( !$this->mQueryDone ) {
+ $this->doQuery();
+ }
+ return $this->mResult->numRows();
+ }
+
+ /**
+ * Get a URL query array for the prev, next, first and last links.
+ *
+ * @return array
+ */
+ function getPagingQueries() {
+ if ( !$this->mQueryDone ) {
+ $this->doQuery();
+ }
+
+ # Don't announce the limit everywhere if it's the default
+ $urlLimit = $this->mLimit == $this->mDefaultLimit ? null : $this->mLimit;
+
+ if ( $this->mIsFirst ) {
+ $prev = false;
+ $first = false;
+ } else {
+ $prev = array(
+ 'dir' => 'prev',
+ 'offset' => $this->mFirstShown,
+ 'limit' => $urlLimit
+ );
+ $first = array( 'limit' => $urlLimit );
+ }
+ if ( $this->mIsLast ) {
+ $next = false;
+ $last = false;
+ } else {
+ $next = array( 'offset' => $this->mLastShown, 'limit' => $urlLimit );
+ $last = array( 'dir' => 'prev', 'limit' => $urlLimit );
+ }
+ return array(
+ 'prev' => $prev,
+ 'next' => $next,
+ 'first' => $first,
+ 'last' => $last
+ );
+ }
+
+ /**
+ * Returns whether to show the "navigation bar"
+ *
+ * @return bool
+ */
+ function isNavigationBarShown() {
+ if ( !$this->mQueryDone ) {
+ $this->doQuery();
+ }
+ // Hide navigation by default if there is nothing to page
+ return !( $this->mIsFirst && $this->mIsLast );
+ }
+
+ /**
+ * Get paging links. If a link is disabled, the item from $disabledTexts
+ * will be used. If there is no such item, the unlinked text from
+ * $linkTexts will be used. Both $linkTexts and $disabledTexts are arrays
+ * of HTML.
+ *
+ * @param array $linkTexts
+ * @param array $disabledTexts
+ * @return array
+ */
+ function getPagingLinks( $linkTexts, $disabledTexts = array() ) {
+ $queries = $this->getPagingQueries();
+ $links = array();
+
+ foreach ( $queries as $type => $query ) {
+ if ( $query !== false ) {
+ $links[$type] = $this->makeLink(
+ $linkTexts[$type],
+ $queries[$type],
+ $type
+ );
+ } elseif ( isset( $disabledTexts[$type] ) ) {
+ $links[$type] = $disabledTexts[$type];
+ } else {
+ $links[$type] = $linkTexts[$type];
+ }
+ }
+
+ return $links;
+ }
+
+ function getLimitLinks() {
+ $links = array();
+ if ( $this->mIsBackwards ) {
+ $offset = $this->mPastTheEndIndex;
+ } else {
+ $offset = $this->mOffset;
+ }
+ foreach ( $this->mLimitsShown as $limit ) {
+ $links[] = $this->makeLink(
+ $this->getLanguage()->formatNum( $limit ),
+ array( 'offset' => $offset, 'limit' => $limit ),
+ 'num'
+ );
+ }
+ return $links;
+ }
+
+ /**
+ * Abstract formatting function. This should return an HTML string
+ * representing the result row $row. Rows will be concatenated and
+ * returned by getBody()
+ *
+ * @param array|stdClass $row Database row
+ * @return string
+ */
+ abstract function formatRow( $row );
+
+ /**
+ * This function should be overridden to provide all parameters
+ * needed for the main paged query. It returns an associative
+ * array with the following elements:
+ * tables => Table(s) for passing to Database::select()
+ * fields => Field(s) for passing to Database::select(), may be *
+ * conds => WHERE conditions
+ * options => option array
+ * join_conds => JOIN conditions
+ *
+ * @return array
+ */
+ abstract function getQueryInfo();
+
+ /**
+ * This function should be overridden to return the name of the index fi-
+ * eld. If the pager supports multiple orders, it may return an array of
+ * 'querykey' => 'indexfield' pairs, so that a request with &count=querykey
+ * will use indexfield to sort. In this case, the first returned key is
+ * the default.
+ *
+ * Needless to say, it's really not a good idea to use a non-unique index
+ * for this! That won't page right.
+ *
+ * @return string|array
+ */
+ abstract function getIndexField();
+
+ /**
+ * This function should be overridden to return the names of secondary columns
+ * to order by in addition to the column in getIndexField(). These fields will
+ * not be used in the pager offset or in any links for users.
+ *
+ * If getIndexField() returns an array of 'querykey' => 'indexfield' pairs then
+ * this must return a corresponding array of 'querykey' => array( fields...) pairs
+ * in order for a request with &count=querykey to use array( fields...) to sort.
+ *
+ * This is useful for pagers that GROUP BY a unique column (say page_id)
+ * and ORDER BY another (say page_len). Using GROUP BY and ORDER BY both on
+ * page_len,page_id avoids temp tables (given a page_len index). This would
+ * also work if page_id was non-unique but we had a page_len,page_id index.
+ *
+ * @return array
+ */
+ protected function getExtraSortFields() {
+ return array();
+ }
+
+ /**
+ * Return the default sorting direction: DIR_ASCENDING or DIR_DESCENDING.
+ * You can also have an associative array of ordertype => dir,
+ * if multiple order types are supported. In this case getIndexField()
+ * must return an array, and the keys of that must exactly match the keys
+ * of this.
+ *
+ * For backward compatibility, this method's return value will be ignored
+ * if $this->mDefaultDirection is already set when the constructor is
+ * called, for instance if it's statically initialized. In that case the
+ * value of that variable (which must be a boolean) will be used.
+ *
+ * Note that despite its name, this does not return the value of the
+ * $this->mDefaultDirection member variable. That's the default for this
+ * particular instantiation, which is a single value. This is the set of
+ * all defaults for the class.
+ *
+ * @return bool
+ */
+ protected function getDefaultDirections() {
+ return IndexPager::DIR_ASCENDING;
+ }
+}