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<?php

/**

 * CodeIgniter

 *

 * An open source application development framework for PHP

 *

 * This content is released under the MIT License (MIT)

 *

 * Copyright (c) 2014 - 2019, British Columbia Institute of Technology

 *

 * Permission is hereby granted, free of charge, to any person obtaining a copy

 * of this software and associated documentation files (the "Software"), to deal

 * in the Software without restriction, including without limitation the rights

 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

 * copies of the Software, and to permit persons to whom the Software is

 * furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

 * THE SOFTWARE.

 *

 * @package	CodeIgniter

 * @author	EllisLab Dev Team

 * @copyright	Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)

 * @copyright	Copyright (c) 2014 - 2019, British Columbia Institute of Technology (https://bcit.ca/)

 * @license	https://opensource.org/licenses/MIT	MIT License

 * @link	https://codeigniter.com

 * @since	Version 2.0.3

 * @filesource

 */

defined('BASEPATH') OR exit('No direct script access allowed');

/**

 * SQLSRV Database Adapter Class

 *

 * Note: _DB is an extender class that the app controller

 * creates dynamically based on whether the query builder

 * class is being used or not.

 *

 * @package		CodeIgniter

 * @subpackage	Drivers

 * @category	Database

 * @author		EllisLab Dev Team

 * @link		https://codeigniter.com/user_guide/database/

 */

class CI_DB_sqlsrv_driver extends CI_DB {

	/**

	 * Database driver

	 *

	 * @var	string

	 */

	public $dbdriver = 'sqlsrv';

	/**

	 * Scrollable flag

	 *

	 * Determines what cursor type to use when executing queries.

	 *

	 * FALSE or SQLSRV_CURSOR_FORWARD would increase performance,

	 * but would disable num_rows() (and possibly insert_id())

	 *

	 * @var	mixed

	 */

	public $scrollable;

	// --------------------------------------------------------------------

	/**

	 * ORDER BY random keyword

	 *

	 * @var	array

	 */

	protected $_random_keyword = array('NEWID()', 'RAND(%d)');

	/**

	 * Quoted identifier flag

	 *

	 * Whether to use SQL-92 standard quoted identifier

	 * (double quotes) or brackets for identifier escaping.

	 *

	 * @var	bool

	 */

	protected $_quoted_identifier = TRUE;

	// --------------------------------------------------------------------

	/**

	 * Class constructor

	 *

	 * @param	array	$params

	 * @return	void

	 */

	public function __construct($params)

	{

		parent::__construct($params);

		// This is only supported as of SQLSRV 3.0

		if ($this->scrollable === NULL)

		{

			$this->scrollable = defined('SQLSRV_CURSOR_CLIENT_BUFFERED')

				? SQLSRV_CURSOR_CLIENT_BUFFERED

				: FALSE;

		}

	}

	// --------------------------------------------------------------------

	/**

	 * Database connection

	 *

	 * @param	bool	$pooling

	 * @return	resource

	 */

	public function db_connect($pooling = FALSE)

	{

		$charset = in_array(strtolower($this->char_set), array('utf-8', 'utf8'), TRUE)

			? 'UTF-8' : SQLSRV_ENC_CHAR;

		$connection = array(

			'UID'			=> empty($this->username) ? '' : $this->username,

			'PWD'			=> empty($this->password) ? '' : $this->password,

			'Database'		=> $this->database,

			'ConnectionPooling'	=> ($pooling === TRUE) ? 1 : 0,

			'CharacterSet'		=> $charset,

			'Encrypt'		=> ($this->encrypt === TRUE) ? 1 : 0,

			'ReturnDatesAsStrings'	=> 1

		);

		// If the username and password are both empty, assume this is a

		// 'Windows Authentication Mode' connection.

		if (empty($connection['UID']) && empty($connection['PWD']))

		{

			unset($connection['UID'], $connection['PWD']);

		}

		if (FALSE !== ($this->conn_id = sqlsrv_connect($this->hostname, $connection)))

		{

			// Determine how identifiers are escaped

			$query = $this->query('SELECT CASE WHEN (@@OPTIONS | 256) = @@OPTIONS THEN 1 ELSE 0 END AS qi');

			$query = $query->row_array();

			$this->_quoted_identifier = empty($query) ? FALSE : (bool) $query['qi'];

			$this->_escape_char = ($this->_quoted_identifier) ? '"' : array('[', ']');

		}

		return $this->conn_id;

	}

	// --------------------------------------------------------------------

	/**

	 * Select the database

	 *

	 * @param	string	$database

	 * @return	bool

	 */

	public function db_select($database = '')

	{

		if ($database === '')

		{

			$database = $this->database;

		}

		if ($this->_execute('USE '.$this->escape_identifiers($database)))

		{

			$this->database = $database;

			$this->data_cache = array();

			return TRUE;

		}

		return FALSE;

	}

	// --------------------------------------------------------------------

	/**

	 * Execute the query

	 *

	 * @param	string	$sql	an SQL query

	 * @return	resource

	 */

	protected function _execute($sql)

	{

		return ($this->scrollable === FALSE OR $this->is_write_type($sql))

			? sqlsrv_query($this->conn_id, $sql)

			: sqlsrv_query($this->conn_id, $sql, NULL, array('Scrollable' => $this->scrollable));

	}

	// --------------------------------------------------------------------

	/**

	 * Begin Transaction

	 *

	 * @return	bool

	 */

	protected function _trans_begin()

	{

		return sqlsrv_begin_transaction($this->conn_id);

	}

	// --------------------------------------------------------------------

	/**

	 * Commit Transaction

	 *

	 * @return	bool

	 */

	protected function _trans_commit()

	{

		return sqlsrv_commit($this->conn_id);

	}

	// --------------------------------------------------------------------

	/**

	 * Rollback Transaction

	 *

	 * @return	bool

	 */

	protected function _trans_rollback()

	{

		return sqlsrv_rollback($this->conn_id);

	}

	// --------------------------------------------------------------------

	/**

	 * Affected Rows

	 *

	 * @return	int

	 */

	public function affected_rows()

	{

		return sqlsrv_rows_affected($this->result_id);

	}

	// --------------------------------------------------------------------

	/**

	 * Insert ID

	 *

	 * Returns the last id created in the Identity column.

	 *

	 * @return	string

	 */

	public function insert_id()

	{

		return $this->query('SELECT SCOPE_IDENTITY() AS insert_id')->row()->insert_id;

	}

	// --------------------------------------------------------------------

	/**

	 * Database version number

	 *

	 * @return	string

	 */

	public function version()

	{

		if (isset($this->data_cache['version']))

		{

			return $this->data_cache['version'];

		}

		if ( ! $this->conn_id OR ($info = sqlsrv_server_info($this->conn_id)) === FALSE)

		{

			return FALSE;

		}

		return $this->data_cache['version'] = $info['SQLServerVersion'];

	}

	// --------------------------------------------------------------------

	/**

	 * List table query

	 *

	 * Generates a platform-specific query string so that the table names can be fetched

	 *

	 * @param	bool

	 * @return	string	$prefix_limit

	 */

	protected function _list_tables($prefix_limit = FALSE)

	{

		$sql = 'SELECT '.$this->escape_identifiers('name')

			.' FROM '.$this->escape_identifiers('sysobjects')

			.' WHERE '.$this->escape_identifiers('type')." = 'U'";

		if ($prefix_limit === TRUE && $this->dbprefix !== '')

		{

			$sql .= ' AND '.$this->escape_identifiers('name')." LIKE '".$this->escape_like_str($this->dbprefix)."%' "

				.sprintf($this->_escape_like_str, $this->_escape_like_chr);

		}

		return $sql.' ORDER BY '.$this->escape_identifiers('name');

	}

	// --------------------------------------------------------------------

	/**

	 * List column query

	 *

	 * Generates a platform-specific query string so that the column names can be fetched

	 *

	 * @param	string	$table

	 * @return	string

	 */

	protected function _list_columns($table = '')

	{

		return 'SELECT COLUMN_NAME

			FROM INFORMATION_SCHEMA.Columns

			WHERE UPPER(TABLE_NAME) = '.$this->escape(strtoupper($table));

	}

	// --------------------------------------------------------------------

	/**

	 * Returns an object with field data

	 *

	 * @param	string	$table

	 * @return	array

	 */

	public function field_data($table)

	{

		$sql = 'SELECT COLUMN_NAME, DATA_TYPE, CHARACTER_MAXIMUM_LENGTH, NUMERIC_PRECISION, COLUMN_DEFAULT

			FROM INFORMATION_SCHEMA.Columns

			WHERE UPPER(TABLE_NAME) = '.$this->escape(strtoupper($table));

		if (($query = $this->query($sql)) === FALSE)

		{

			return FALSE;

		}

		$query = $query->result_object();

		$retval = array();

		for ($i = 0, $c = count($query); $i < $c; $i++)

		{

			$retval[$i]			= new stdClass();

			$retval[$i]->name		= $query[$i]->COLUMN_NAME;

			$retval[$i]->type		= $query[$i]->DATA_TYPE;

			$retval[$i]->max_length		= ($query[$i]->CHARACTER_MAXIMUM_LENGTH > 0) ? $query[$i]->CHARACTER_MAXIMUM_LENGTH : $query[$i]->NUMERIC_PRECISION;

			$retval[$i]->default		= $query[$i]->COLUMN_DEFAULT;

		}

		return $retval;

	}

	// --------------------------------------------------------------------

	/**

	 * Error

	 *

	 * Returns an array containing code and message of the last

	 * database error that has occurred.

	 *

	 * @return	array

	 */

	public function error()

	{

		$error = array('code' => '00000', 'message' => '');

		$sqlsrv_errors = sqlsrv_errors(SQLSRV_ERR_ERRORS);

		if ( ! is_array($sqlsrv_errors))

		{

			return $error;

		}

		$sqlsrv_error = array_shift($sqlsrv_errors);

		if (isset($sqlsrv_error['SQLSTATE']))

		{

			$error['code'] = isset($sqlsrv_error['code']) ? $sqlsrv_error['SQLSTATE'].'/'.$sqlsrv_error['code'] : $sqlsrv_error['SQLSTATE'];

		}

		elseif (isset($sqlsrv_error['code']))

		{

			$error['code'] = $sqlsrv_error['code'];

		}

		if (isset($sqlsrv_error['message']))

		{

			$error['message'] = $sqlsrv_error['message'];

		}

		return $error;

	}

	// --------------------------------------------------------------------

	/**

	 * Update statement

	 *

	 * Generates a platform-specific update string from the supplied data

	 *

	 * @param	string	$table

	 * @param	array	$values

	 * @return	string

	 */

	protected function _update($table, $values)

	{

		$this->qb_limit = FALSE;

		$this->qb_orderby = array();

		return parent::_update($table, $values);

	}

	// --------------------------------------------------------------------

	/**

	 * Truncate statement

	 *

	 * Generates a platform-specific truncate string from the supplied data

	 *

	 * If the database does not support the TRUNCATE statement,

	 * then this method maps to 'DELETE FROM table'

	 *

	 * @param	string	$table

	 * @return	string

	 */

	protected function _truncate($table)

	{

		return 'TRUNCATE TABLE '.$table;

	}

	// --------------------------------------------------------------------

	/**

	 * Delete statement

	 *

	 * Generates a platform-specific delete string from the supplied data

	 *

	 * @param	string	$table

	 * @return	string

	 */

	protected function _delete($table)

	{

		if ($this->qb_limit)

		{

			return 'WITH ci_delete AS (SELECT TOP '.$this->qb_limit.' * FROM '.$table.$this->_compile_wh('qb_where').') DELETE FROM ci_delete';

		}

		return parent::_delete($table);

	}

	// --------------------------------------------------------------------

	/**

	 * LIMIT

	 *

	 * Generates a platform-specific LIMIT clause

	 *

	 * @param	string	$sql	SQL Query

	 * @return	string

	 */

	protected function _limit($sql)

	{

		// As of SQL Server 2012 (11.0.*) OFFSET is supported

		if (version_compare($this->version(), '11', '>='))

		{

			// SQL Server OFFSET-FETCH can be used only with the ORDER BY clause

			empty($this->qb_orderby) && $sql .= ' ORDER BY 1';

			return $sql.' OFFSET '.(int) $this->qb_offset.' ROWS FETCH NEXT '.$this->qb_limit.' ROWS ONLY';

		}

		$limit = $this->qb_offset + $this->qb_limit;

		// An ORDER BY clause is required for ROW_NUMBER() to work

		if ($this->qb_offset && ! empty($this->qb_orderby))

		{

			$orderby = $this->_compile_order_by();

			// We have to strip the ORDER BY clause

			$sql = trim(substr($sql, 0, strrpos($sql, $orderby)));

			// Get the fields to select from our subquery, so that we can avoid CI_rownum appearing in the actual results

			if (count($this->qb_select) === 0 OR strpos(implode(',', $this->qb_select), '*') !== FALSE)

			{

				$select = '*'; // Inevitable

			}

			else

			{

				// Use only field names and their aliases, everything else is out of our scope.

				$select = array();

				$field_regexp = ($this->_quoted_identifier)

					? '("[^\"]+")' : '(\[[^\]]+\])';

				for ($i = 0, $c = count($this->qb_select); $i < $c; $i++)

				{

					$select[] = preg_match('/(?:\s|\.)'.$field_regexp.'$/i', $this->qb_select[$i], $m)

						? $m[1] : $this->qb_select[$i];

				}

				$select = implode(', ', $select);

			}

			return 'SELECT '.$select." FROM (\n\n"

				.preg_replace('/^(SELECT( DISTINCT)?)/i', '\\1 ROW_NUMBER() OVER('.trim($orderby).') AS '.$this->escape_identifiers('CI_rownum').', ', $sql)

				."\n\n) ".$this->escape_identifiers('CI_subquery')

				."\nWHERE ".$this->escape_identifiers('CI_rownum').' BETWEEN '.($this->qb_offset + 1).' AND '.$limit;

		}

		return preg_replace('/(^\SELECT (DISTINCT)?)/i','\\1 TOP '.$limit.' ', $sql);

	}

	// --------------------------------------------------------------------

	/**

	 * Insert batch statement

	 *

	 * Generates a platform-specific insert string from the supplied data.

	 *

	 * @param	string	$table	Table name

	 * @param	array	$keys	INSERT keys

	 * @param	array	$values	INSERT values

	 * @return	string|bool

	 */

	protected function _insert_batch($table, $keys, $values)

	{

		// Multiple-value inserts are only supported as of SQL Server 2008

		if (version_compare($this->version(), '10', '>='))

		{

			return parent::_insert_batch($table, $keys, $values);

		}

		return ($this->db_debug) ? $this->display_error('db_unsupported_feature') : FALSE;

	}

	// --------------------------------------------------------------------

	/**

	 * Close DB Connection

	 *

	 * @return	void

	 */

	protected function _close()

	{

		sqlsrv_close($this->conn_id);

	}

}