/**
* 过滤数组键值
*
* @access private
* @param string $str 待处理字段值
* @return string
*/
private function filterColumn($str)
{
$str = $str . ' 0';
$length = strlen($str);
$lastIsAlnum = false;
$result = '';
$word = '';
$split = '';
$quotes = 0;
for ($i = 0; $i < $length; $i++) {
$cha = $str[$i];
if (ctype_alnum($cha) || false !== strpos('_*', $cha)) {
if (!$lastIsAlnum) {
if ($quotes > 0 && !ctype_digit($word) && '.' != $split && false === strpos(self::KEYWORDS, strtoupper($word))) {
$word = $this->_adapter->quoteColumn($word);
} else {
if ('.' == $split && 'table' == $word) {
$word = $this->_prefix;
$split = '';
}
}
$result .= $word . $split;
$word = '';
$quotes = 0;
}
$word .= $cha;
$lastIsAlnum = true;
} else {
if ($lastIsAlnum) {
if (0 == $quotes) {
if (false !== strpos(' ,)=<>.+-*/', $cha)) {
$quotes = 1;
} else {
if ('(' == $cha) {
$quotes = -1;
}
}
}
$split = '';
}
$split .= $cha;
$lastIsAlnum = false;
}
}
return $result;
}