/**
     * Automaticaly generates an insert or update query and pass it to prepare()
     *
     * @param string $table         the table name
     * @param array  $table_fields  the array of field names
     * @param int    $mode          a type of query to make:
     *                               DB_AUTOQUERY_INSERT or DB_AUTOQUERY_UPDATE
     * @param string $where         for update queries: the WHERE clause to
     *                               append to the SQL statement.  Don't
     *                               include the "WHERE" keyword.
     *
     * @return resource  the query handle
     *
     * @uses DB_common::prepare(), DB_common::buildManipSQL()
     */
    function autoPrepare($table, $table_fields, $mode = DB_AUTOQUERY_INSERT,
                         $where = false)
    {
        $query = $this->buildManipSQL($table, $table_fields, $mode, $where);
        if (DB::isError($query)) {
            return $query;
        }
        return $this->prepare($query);
    }

    // }}}
    // {{{ autoExecute()

    /**
     * Automaticaly generates an insert or update query and call prepare()
     * and execute() with it
     *
     * @param string $table         the table name
     * @param array  $fields_values the associative array where $key is a
     *                               field name and $value its value
     * @param int    $mode          a type of query to make:
     *                               DB_AUTOQUERY_INSERT or DB_AUTOQUERY_UPDATE
     * @param string $where         for update queries: the WHERE clause to
     *                               append to the SQL statement.  Don't
     *                               include the "WHERE" keyword.
     *
     * @return mixed  a new DB_result object for successful SELECT queries
     *                 or DB_OK for successul data manipulation queries.
     *                 A DB_Error object on failure.
     *
     * @uses DB_common::autoPrepare(), DB_common::execute()
     */
    function autoExecute($table, $fields_values, $mode = DB_AUTOQUERY_INSERT,
                         $where = false)
    {
        $sth = $this->autoPrepare($table, array_keys($fields_values), $mode,
                                  $where);
        if (DB::isError($sth)) {
            return $sth;
        }
        $ret =& $this->execute($sth, array_values($fields_values));
        $this->freePrepared($sth);
        return $ret;

    }

    // }}}
    // {{{ buildManipSQL()

    /**
     * Produces an SQL query string for autoPrepare()
     *
     * Example:
     * <pre>
     * buildManipSQL('table_sql', array('field1', 'field2', 'field3'),
     *               DB_AUTOQUERY_INSERT);
     * </pre>
     *
     * That returns
     * <samp>
     * INSERT INTO table_sql (field1,field2,field3) VALUES (?,?,?)
     * </samp>
     *
     * NOTES:
     *   - This belongs more to a SQL Builder class, but this is a simple
     *     facility.
     *   - Be carefull! If you don't give a $where param with an UPDATE
     *     query, all the records of the table will be updated!
     *
     * @param string $table         the table name
     * @param array  $table_fields  the array of field names
     * @param int    $mode          a type of query to make:
     *                               DB_AUTOQUERY_INSERT or DB_AUTOQUERY_UPDATE
     * @param string $where         for update queries: the WHERE clause to
     *                               append to the SQL statement.  Don't
     *                               include the "WHERE" keyword.
     *
     * @return string  the sql query for autoPrepare()
     */
    function buildManipSQL($table, $table_fields, $mode, $where = false)
    {
        if (count($table_fields) == 0) {
            return $this->raiseError(DB_ERROR_NEED_MORE_DATA);
        }
        $first = true;
        switch ($mode) {
            case DB_AUTOQUERY_INSERT:
                $values = '';
                $names = '';
                foreach ($table_fields as $value) {
                    if ($first) {
                        $first = false;
                    } else {
                        $names .= ',';
                        $values .= ',';
                    }
                    $names .= $value;
                    $values .= '?';
                }
                return "INSERT INTO $table ($names) VALUES ($values)";
            case DB_AUTOQUERY_UPDATE:
                $set = '';
                foreach ($table_fields as $value) {
                    if ($first) {
                        $first = false;
                    } else {
                        $set .= ',';
                    }
                    $set .= "$value = ?";
                }
                $sql = "UPDATE $table SET $set";
                if ($where) {
                    $sql .= " WHERE $where";
                }
                return $sql;
            default:
                return $this->raiseError(DB_ERROR_SYNTAX);
        }
    }

    // }}}
    // {{{ execute()

    /**
     * Executes a DB statement prepared with prepare()
     *
     * Example 1.
     * <code>
     * $sth = $db->prepare('INSERT INTO tbl (a, b, c) VALUES (?, !, &)');
     * $data = array(
     *     "John's text",
     *     "'it''s good'",
     *     'filename.txt'
     * );
     * $res =& $db->execute($sth, $data);
     * </code>
     *
     * @param resource $stmt  a DB statement resource returned from prepare()
     * @param mixed    $data  array, string or numeric data to be used in
     *                         execution of the statement.  Quantity of items
     *                         passed must match quantity of placeholders in
     *                         query:  meaning 1 placeholder for non-array
     *                         parameters or 1 placeholder per array element.
     *
     * @return mixed  a new DB_result object for successful SELECT queries
     *                 or DB_OK for successul data manipulation queries.
     *                 A DB_Error object on failure.
     *
     * {@internal ibase and oci8 have their own execute() methods.}}
     *
     * @see DB_common::prepare()
     */
    function &execute($stmt, $data = array())
    {
        $realquery = $this->executeEmulateQuery($stmt, $data);
        if (DB::isError($realquery)) {
            return $realquery;
        }
        $result = $this->simpleQuery($realquery);

        if ($result === DB_OK || DB::isError($result)) {
            return $result;
        } else {
            $tmp =& new DB_result($this, $result);
            return $tmp;
        }
    }

    // }}}
    // {{{ executeEmulateQuery()

    /**
     * Emulates executing prepared statements if the DBMS not support them
     *
     * @param resource $stmt  a DB statement resource returned from execute()
     * @param mixed    $data  array, string or numeric data to be used in
     *                         execution of the statement.  Quantity of items
     *                         passed must match quantity of placeholders in
     *                         query:  meaning 1 placeholder for non-array
     *                         parameters or 1 placeholder per array element.
     *
     * @return mixed  a string containing the real query run when emulating
     *                 prepare/execute.  A DB_Error object on failure.
     *
     * @access protected
     * @see DB_common::execute()
     */
    function executeEmulateQuery($stmt, $data = array())
    {
        $stmt = (int)$stmt;
        $data = (array)$data;
        $this->last_parameters = $data;

        if (count($this->prepare_types[$stmt]) != count($data)) {
            $this->last_query = $this->prepared_queries[$stmt];
            return $this->raiseError(DB_ERROR_MISMATCH);
        }

        $realquery = $this->prepare_tokens[$stmt][0];

        $i = 0;
        foreach ($data as $value) {
            if ($this->prepare_types[$stmt][$i] == DB_PARAM_SCALAR) {
                $realquery .= $this->quoteSmart($value);
            } elseif ($this->prepare_types[$stmt][$i] == DB_PARAM_OPAQUE) {
                $fp = @fopen($value, 'rb');
                if (!$fp) {
                    return $this->raiseError(DB_ERROR_ACCESS_VIOLATION);
                }
                $realquery .= $this->quoteSmart(fread($fp, filesize($value)));
                fclose($fp);
            } else {
                $realquery .= $value;
            }

            $realquery .= $this->prepare_tokens[$stmt][++$i];
        }

        return $realquery;
    }

    // }}}
    // {{{ executeMultiple()

    /**
     * Performs several execute() calls on the same statement handle
     *
     * $data must be an array indexed numerically
     * from 0, one execute call is done for every "row" in the array.
     *
     * If an error occurs during execute(), executeMultiple() does not
     * execute the unfinished rows, but rather returns that error.
     *
     * @param resource $stmt  query handle from prepare()
     * @param array    $data  numeric array containing the
     *                         data to insert into the query
     *
     * @return int  DB_OK on success.  A DB_Error object on failure.
     *
     * @see DB_common::prepare(), DB_common::execute()
     */
    function executeMultiple($stmt, $data)
    {
        foreach ($data as $value) {
            $res =& $this->execute($stmt, $value);
            if (DB::isError($res)) {
                return $res;
            }
        }
        return DB_OK;
    }

    // }}}
    // {{{ freePrepared()

    /**
     * Frees the internal resources associated with a prepared query
     *
     * @param resource $stmt           the prepared statement's PHP resource
     * @param bool     $free_resource  should the PHP resource be freed too?
     *                                  Use false if you need to get data
     *                                  from the result set later.
     *
     * @return bool  TRUE on success, FALSE if $result is invalid
     *
     * @see DB_common::prepare()
     */
    function freePrepared($stmt, $free_resource = true)
    {
        $stmt = (int)$stmt;
        if (isset($this->prepare_tokens[$stmt])) {
            unset($this->prepare_tokens[$stmt]);
            unset($this->prepare_types[$stmt]);
            unset($this->prepared_queries[$stmt]);
            return true;
        }
        return false;
    }

    // }}}
    // {{{ modifyQuery()

    /**
     * Changes a query string for various DBMS specific reasons
     *
     * It is defined here to ensure all drivers have this method available.
     *
     * @param string $query  the query string to modify
     *
     * @return string  the modified query string
     *
     * @access protected
     * @see DB_mysql::modifyQuery(), DB_oci8::modifyQuery(),
     *      DB_sqlite::modifyQuery()
     */
    function modifyQuery($query)
    {
        return $query;
    }

    // }}}
    // {{{ modifyLimitQuery()

    /**
     * Adds LIMIT clauses to a query string according to current DBMS standards
     *
     * It is defined here to assure that all implementations
     * have this method defined.
     *
     * @param string $query   the query to modify
     * @param int    $from    the row to start to fetching (0 = the first row)
     * @param int    $count   the numbers of rows to fetch
     * @param mixed  $params  array, string or numeric data to be used in
     *                         execution of the statement.  Quantity of items
     *                         passed must match quantity of placeholders in
     *                         query:  meaning 1 placeholder for non-array
     *                         parameters or 1 placeholder per array element.
     *
     * @return string  the query string with LIMIT clauses added
     *
     * @access protected
     */
    function modifyLimitQuery($query, $from, $count, $params = array())
    {
        return $query;
    }

    // }}}
    // {{{ query()

    /**
     * Sends a query to the database server
     *
     * The query string can be either a normal statement to be sent directly
     * to the server OR if <var>$params</var> are passed the query can have
     * placeholders and it will be passed through prepare() and execute().
     *
     * @param string $query   the SQL query or the statement to prepare
     * @param mixed  $params  array, string or numeric data to be used in
     *                         execution of the statement.  Quantity of items
     *                         passed must match quantity of placeholders in
     *                         query:  meaning 1 placeholder for non-array
     *                         parameters or 1 placeholder per array element.
     *
     * @return mixed  a new DB_result object for successful SELECT queries
     *                 or DB_OK for successul data manipulation queries.
     *                 A DB_Error object on failure.
     *
     * @see DB_result, DB_common::prepare(), DB_common::execute()
     */
    function &query($query, $params = array())
    {
        if (sizeof($params) > 0) {
            $sth = $this->prepare($query);
            if (DB::isError($sth)) {
                return $sth;
            }
            $ret =& $this->execute($sth, $params);
            $this->freePrepared($sth, false);
            return $ret;
        } else {
            $this->last_parameters = array();
            $result = $this->simpleQuery($query);
            if ($result === DB_OK || DB::isError($result)) {
                return $result;
            } else {
                $tmp =& new DB_result($this, $result);
                return $tmp;
            }
        }
    }

    // }}}
    // {{{ limitQuery()

    /**
     * Generates and executes a LIMIT query