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<?php

/*

 *  $Id: PropelPDO.php 1262 2009-10-26 20:54:39Z francois $

 *

 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 *

 * This software consists of voluntary contributions made by many individuals

 * and is licensed under the LGPL. For more information please see

 * <http://propel.phpdb.org>.

 */

/**

 * PDO connection subclass that provides the basic fixes to PDO that are required by Propel.

 *

 * This class was designed to work around the limitation in PDO where attempting to begin

 * a transaction when one has already been begun will trigger a PDOException.  Propel

 * relies on the ability to create nested transactions, even if the underlying layer

 * simply ignores these (because it doesn't support nested transactions).

 *

 * The changes that this class makes to the underlying API include the addition of the

 * getNestedTransactionDepth() and isInTransaction() and the fact that beginTransaction()

 * will no longer throw a PDOException (or trigger an error) if a transaction is already

 * in-progress.

 *

 * @author     Cameron Brunner <cameron.brunner@gmail.com>

 * @author     Hans Lellelid <hans@xmpl.org>

 * @author     Christian Abegg <abegg.ch@gmail.com>

 * @since      2006-09-22

 * @package    propel.util

 */

class PropelPDO extends PDO {

	/**

	 * Attribute to use to set whether to cache prepared statements.

	 */

	const PROPEL_ATTR_CACHE_PREPARES = -1;

	/**

	 * The current transaction depth.

	 * @var        int

	 */

	protected $nestedTransactionCount = 0;

	/**

	 * Cache of prepared statements (PDOStatement) keyed by md5 of SQL.

	 *

	 * @var        array [md5(sql) => PDOStatement]

	 */

	protected $preparedStatements = array();

	/**

	 * Whether to cache prepared statements.

	 *

	 * @var        boolean

	 */

	protected $cachePreparedStatements = false;

	/**

	 * Whether the final commit is possible

	 * Is false if a nested transaction is rolled back

	 */

	protected $isUncommitable = false;

	/**

	 * Gets the current transaction depth.

	 * @return     int

	 */

	public function getNestedTransactionCount()

	{

		return $this->nestedTransactionCount;

	}

	/**

	 * Set the current transaction depth.

	 * @param      int $v The new depth.

	 */

	protected function setNestedTransactionCount($v)

	{

		$this->nestedTransactionCount = $v;

	}

	/**

	 * Decrements the current transaction depth by one.

	 */

	protected function decrementNestedTransactionCount()

	{

		$this->nestedTransactionCount--;

	}

	/**

	 * Increments the current transaction depth by one.

	 */

	protected function incrementNestedTransactionCount()

	{

		$this->nestedTransactionCount++;

	}

	/**

	 * Is this PDO connection currently in-transaction?

	 * This is equivalent to asking whether the current nested transaction count

	 * is greater than 0.

	 * @return     boolean

	 */

	public function isInTransaction()

	{

		return ($this->getNestedTransactionCount() > 0);

	}

	/**

	 * Overrides PDO::beginTransaction() to prevent errors due to already-in-progress transaction.

	 */

	public function beginTransaction()

	{

		$return = true;

		$opcount = $this->getNestedTransactionCount();

		if ( $opcount === 0 ) {

			$return = parent::beginTransaction();

			$this->isUncommitable = false;

		}

		$this->incrementNestedTransactionCount();

		return $return;

	}

	/**

	 * Overrides PDO::commit() to only commit the transaction if we are in the outermost

	 * transaction nesting level.

	 */

	public function commit()

	{

		$return = true;

		$opcount = $this->getNestedTransactionCount();

		if ($opcount > 0) {

			if ($opcount === 1) {

				if ($this->isUncommitable) {

					throw new PropelException('Cannot commit because a nested transaction was rolled back');

				} else {

					$return = parent::commit();

				}

			}

			$this->decrementNestedTransactionCount();

		}

		return $return;

	}

	/**

	 * Overrides PDO::rollBack() to only rollback the transaction if we are in the outermost

	 * transaction nesting level

	 * @return     boolean Whether operation was successful.

	 */

	public function rollBack()

	{

		$return = true;

		$opcount = $this->getNestedTransactionCount();

		if ($opcount > 0) {

			if ($opcount === 1) {

				$return = parent::rollBack();

			} else {

				$this->isUncommitable = true;

			}

			$this->decrementNestedTransactionCount();

		}

		return $return;

	}

	/**

	* Rollback the whole transaction, even if this is a nested rollback

	* and reset the nested transaction count to 0.

	* @return     boolean Whether operation was successful.

	*/

	public function forceRollBack()

	{

		$return = true;

		$opcount = $this->getNestedTransactionCount();

		if ($opcount > 0) {

			// If we're in a transaction, always roll it back

			// regardless of nesting level.

			$return = parent::rollBack();

			// reset nested transaction count to 0 so that we don't

			// try to commit (or rollback) the transaction outside this scope.

			$this->nestedTransactionCount = 0;

		}

		return $return;

	}

	/**

	 * Sets a connection attribute.

	 *

	 * This is overridden here to provide support for setting Propel-specific attributes

	 * too.

	 *

	 * @param      int $attribute The attribute to set (e.g. PropelPDO::PROPEL_ATTR_CACHE_PREPARES).

	 * @param      mixed $value The attribute value.

	 */

	public function setAttribute($attribute, $value)

	{

		switch($attribute) {

			case self::PROPEL_ATTR_CACHE_PREPARES:

				$this->cachePreparedStatements = $value;

				break;

			default:

				parent::setAttribute($attribute, $value);

		}

	}

	/**

	 * Gets a connection attribute.

	 *

	 * This is overridden here to provide support for setting Propel-specific attributes

	 * too.

	 *

	 * @param      int $attribute The attribute to get (e.g. PropelPDO::PROPEL_ATTR_CACHE_PREPARES).

	 */

	public function getAttribute($attribute)

	{

		switch($attribute) {

			case self::PROPEL_ATTR_CACHE_PREPARES:

				return $this->cachePreparedStatements;

				break;

			default:

				return parent::getAttribute($attribute);

		}

	}

	/**

	 * Overrides PDO::prepare() to add query caching support if the

	 * PropelPDO::PROPEL_ATTR_CACHE_PREPARES was set to true.

	 * .

	 * @param      string $sql

	 * @param      array

	 * @return     PDOStatement

	 */

	public function prepare($sql, $driver_options = array())

	{

		if ($this->cachePreparedStatements) {

			$key = $sql;

			if (!isset($this->preparedStatements[$key])) {

				$stmt = parent::prepare($sql, $driver_options);

				$this->preparedStatements[$key] = $stmt;

				return $stmt;

			} else {

				return $this->preparedStatements[$key];

			}

		} else {

			return parent::prepare($sql, $driver_options);

		}

	}

	/**

	 * Clears any stored prepared statements for this connection.

	 */

	public function clearStatementCache()

	{

		$this->preparedStatements = array();

	}

}