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[mediawiki.git] / includes / db / DatabaseUtility.php

<?php
/**
 * This file contains database-related utility classes.
 *
 * 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 Database
 */

/**
 * Utility class
 * @ingroup Database
 *
 * This allows us to distinguish a blob from a normal string and an array of strings
 */
class Blob {
        /** @var string */
        protected $mData;

        function __construct( $data ) {
                $this->mData = $data;
        }

        function fetch() {
                return $this->mData;
        }
}

/**
 * Base for all database-specific classes representing information about database fields
 * @ingroup Database
 */
interface Field {
        /**
         * Field name
         * @return string
         */
        function name();

        /**
         * Name of table this field belongs to
         * @return string
         */
        function tableName();

        /**
         * Database type
         * @return string
         */
        function type();

        /**
         * Whether this field can store NULL values
         * @return bool
         */
        function isNullable();
}

/**
 * Result wrapper for grabbing data queried by someone else
 * @ingroup Database
 */
class ResultWrapper implements Iterator {
        /** @var resource */
        public $result;

        /** @var DatabaseBase */
        protected $db;

        /** @var int */
        protected $pos = 0;

        /** @var object|null */
        protected $currentRow = null;

        /**
         * Create a new result object from a result resource and a Database object
         *
         * @param DatabaseBase $database
         * @param resource|ResultWrapper $result
         */
        function __construct( $database, $result ) {
                $this->db = $database;

                if ( $result instanceof ResultWrapper ) {
                        $this->result = $result->result;
                } else {
                        $this->result = $result;
                }
        }

        /**
         * Get the number of rows in a result object
         *
         * @return int
         */
        function numRows() {
                return $this->db->numRows( $this );
        }

        /**
         * Fetch the next row from the given result object, in object form. Fields can be retrieved with
         * $row->fieldname, with fields acting like member variables. If no more rows are available,
         * false is returned.
         *
         * @return stdClass|bool
         * @throws DBUnexpectedError Thrown if the database returns an error
         */
        function fetchObject() {
                return $this->db->fetchObject( $this );
        }

        /**
         * Fetch the next row from the given result object, in associative array form. Fields are
         * retrieved with $row['fieldname']. If no more rows are available, false is returned.
         *
         * @return array|bool
         * @throws DBUnexpectedError Thrown if the database returns an error
         */
        function fetchRow() {
                return $this->db->fetchRow( $this );
        }

        /**
         * Free a result object
         */
        function free() {
                $this->db->freeResult( $this );
                unset( $this->result );
                unset( $this->db );
        }

        /**
         * Change the position of the cursor in a result object.
         * See mysql_data_seek()
         *
         * @param int $row
         */
        function seek( $row ) {
                $this->db->dataSeek( $this, $row );
        }

        /*
         * ======= Iterator functions =======
         * Note that using these in combination with the non-iterator functions
         * above may cause rows to be skipped or repeated.
         */

        function rewind() {
                if ( $this->numRows() ) {
                        $this->db->dataSeek( $this, 0 );
                }
                $this->pos = 0;
                $this->currentRow = null;
        }

        /**
         * @return stdClass|array|bool
         */
        function current() {
                if ( is_null( $this->currentRow ) ) {
                        $this->next();
                }

                return $this->currentRow;
        }

        /**
         * @return int
         */
        function key() {
                return $this->pos;
        }

        /**
         * @return stdClass
         */
        function next() {
                $this->pos++;
                $this->currentRow = $this->fetchObject();

                return $this->currentRow;
        }

        /**
         * @return bool
         */
        function valid() {
                return $this->current() !== false;
        }
}

/**
 * Overloads the relevant methods of the real ResultsWrapper so it
 * doesn't go anywhere near an actual database.
 */
class FakeResultWrapper extends ResultWrapper {
        /** @var array */
        public $result = array();

        /** @var null And it's going to stay that way :D */
        protected $db = null;

        /** @var int */
        protected $pos = 0;

        /** @var array|stdClass|bool */
        protected $currentRow = null;

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

        /**
         * @return int
         */
        function numRows() {
                return count( $this->result );
        }

        /**
         * @return array|bool
         */
        function fetchRow() {
                if ( $this->pos < count( $this->result ) ) {
                        $this->currentRow = $this->result[$this->pos];
                } else {
                        $this->currentRow = false;
                }
                $this->pos++;
                if ( is_object( $this->currentRow ) ) {
                        return get_object_vars( $this->currentRow );
                } else {
                        return $this->currentRow;
                }
        }

        function seek( $row ) {
                $this->pos = $row;
        }

        function free() {
        }

        /**
         * Callers want to be able to access fields with $this->fieldName
         * @return bool|stdClass
         */
        function fetchObject() {
                $this->fetchRow();
                if ( $this->currentRow ) {
                        return (object)$this->currentRow;
                } else {
                        return false;
                }
        }

        function rewind() {
                $this->pos = 0;
                $this->currentRow = null;
        }

        /**
         * @return bool|stdClass
         */
        function next() {
                return $this->fetchObject();
        }
}

/**
 * Used by DatabaseBase::buildLike() to represent characters that have special
 * meaning in SQL LIKE clauses and thus need no escaping. Don't instantiate it
 * manually, use DatabaseBase::anyChar() and anyString() instead.
 */
class LikeMatch {
        /** @var string */
        private $str;

        /**
         * Store a string into a LikeMatch marker object.
         *
         * @param string $s
         */
        public function __construct( $s ) {
                $this->str = $s;
        }

        /**
         * Return the original stored string.
         *
         * @return string
         */
        public function toString() {
                return $this->str;
        }
}

/**
 * An object representing a master or slave position in a replicated setup.
 *
 * The implementation details of this opaque type are up to the database subclass.
 */
interface DBMasterPos {
        /**
         * @return float UNIX timestamp
         * @since 1.25
         */
        public function asOfTime();

        /**
         * @param DBMasterPos $pos
         * @return bool Whether this position is at or higher than $pos
         * @since 1.27
         */
        public function hasReached( DBMasterPos $pos );

        /**
         * @return string
         * @since 1.27
         */
        public function __toString();
}