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<?php
/**
* Parses a reference to a LOCK expression.
*/
namespace PhpMyAdmin\SqlParser\Components;
use PhpMyAdmin\SqlParser\Component;
use PhpMyAdmin\SqlParser\Parser;
use PhpMyAdmin\SqlParser\Token;
use PhpMyAdmin\SqlParser\TokensList;
/**
* Parses a reference to a LOCK expression.
*
* @category Components
*
* @license https://www.gnu.org/licenses/gpl-2.0.txt GPL-2.0+
*/
class LockExpression extends Component
{
/**
* The table to be locked.
*
* @var Expression
*/
public $table;
/**
* The type of lock to be applied.
*
* @var string
*/
public $type;
/**
* @param Parser $parser the parser that serves as context
* @param TokensList $list the list of tokens that are being parsed
* @param array $options parameters for parsing
*
* @return CaseExpression
*/
public static function parse(Parser $parser, TokensList $list, array $options = array())
{
$ret = new self();
/**
* The state of the parser.
*
* Below are the states of the parser.
*
* 0 ---------------- [ tbl_name ] -----------------> 1
* 1 ---------------- [ lock_type ] ----------------> 2
* 2 -------------------- [ , ] --------------------> break
*
* @var int
*/
$state = 0;
$prevToken = null;
for (; $list->idx < $list->count; ++$list->idx) {
/**
* Token parsed at this moment.
*
* @var Token
*/
$token = $list->tokens[$list->idx];
// End of statement.
if ($token->type === Token::TYPE_DELIMITER
|| ($token->type === Token::TYPE_OPERATOR
&& $token->value === ',')
) {
break;
}
if ($state === 0) {
$ret->table = Expression::parse($parser, $list, array('parseField' => 'table'));
$state = 1;
} elseif ($state === 1) {
// parse lock type
$ret->type = self::parseLockType($parser, $list);
$state = 2;
}
$prevToken = $token;
}
// 2 is the only valid end state
if ($state !== 2) {
$parser->error('Unexpected end of LOCK expression.', $prevToken);
}
--$list->idx;
return $ret;
}
/**
* @param LockExpression|LockExpression[] $component the component to be built
* @param array $options parameters for building
*
* @return string
*/
public static function build($component, array $options = array())
{
if (is_array($component)) {
return implode(', ', $component);
}
return $component->table . ' ' . $component->type;
}
private static function parseLockType(Parser $parser, TokensList $list)
{
$lockType = '';
/**
* The state of the parser while parsing for lock type.
*
* Below are the states of the parser.
*
* 0 ---------------- [ READ ] -----------------> 1
* 0 ------------- [ LOW_PRIORITY ] ------------> 2
* 0 ---------------- [ WRITE ] ----------------> 3
* 1 ---------------- [ LOCAL ] ----------------> 3
* 2 ---------------- [ WRITE ] ----------------> 3
*
* @var int
*/
$state = 0;
$prevToken = null;
for (; $list->idx < $list->count; ++$list->idx) {
/**
* Token parsed at this moment.
*
* @var Token
*/
$token = $list->tokens[$list->idx];
// End of statement.
if ($token->type === Token::TYPE_DELIMITER
|| ($token->type === Token::TYPE_OPERATOR
&& $token->value === ',')
) {
--$list->idx;
break;
}
// Skipping whitespaces and comments.
if ($token->type === Token::TYPE_WHITESPACE || $token->type === Token::TYPE_COMMENT) {
continue;
}
// We only expect keywords
if ($token->type !== Token::TYPE_KEYWORD) {
$parser->error('Unexpected token.', $token);
break;
}
if ($state === 0) {
if ($token->keyword === 'READ') {
$state = 1;
} elseif ($token->keyword === 'LOW_PRIORITY') {
$state = 2;
} elseif ($token->keyword === 'WRITE') {
$state = 3;
} else {
$parser->error('Unexpected keyword.', $token);
break;
}
$lockType .= $token->keyword;
} elseif ($state === 1) {
if ($token->keyword === 'LOCAL') {
$lockType .= ' ' . $token->keyword;
$state = 3;
} else {
$parser->error('Unexpected keyword.', $token);
break;
}
} elseif ($state === 2) {
if ($token->keyword === 'WRITE') {
$lockType .= ' ' . $token->keyword;
$state = 3; // parsing over
} else {
$parser->error('Unexpected keyword.', $token);
break;
}
}
$prevToken = $token;
}
// Only two possible end states
if ($state !== 1 && $state !== 3) {
$parser->error('Unexpected end of Lock expression.', $prevToken);
}
return $lockType;
}
}