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<?php |
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namespace Netdudes\DataSourceryBundle\UQL; |
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use Netdudes\DataSourceryBundle\UQL\AST\ASTArray; |
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use Netdudes\DataSourceryBundle\UQL\AST\ASTAssertion; |
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use Netdudes\DataSourceryBundle\UQL\AST\ASTFunctionCall; |
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use Netdudes\DataSourceryBundle\UQL\AST\ASTGroup; |
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use Netdudes\DataSourceryBundle\UQL\Exception\Semantic\UqlUnexpectedEndOfExpressionException; |
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use Netdudes\DataSourceryBundle\UQL\Exception\Semantic\UqlUnexpectedTokenException; |
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use Netdudes\DataSourceryBundle\UQL\Exception\UQLSyntaxError; |
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/** |
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* Class Parser |
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* |
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* The parser translates a linear stream of tokens into a logical Abstract |
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* Syntax Tree (AST) that represents the logical structure of the language |
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* with independence of the actual end-objects (filters). |
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* |
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* @package Netdudes\NetdudesDataSourceryBundle\UQL |
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*/ |
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class Parser |
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{ |
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/** |
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* |
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* Grammar (<identifier>s and <literal>s are simple scalars defined by regular expressions on the lexer): |
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* |
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* <operator> ::= "<" | ">" | "<=" | ">=" | "!=" | "<>" | "=" |
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* <logic> ::= "AND" | "OR" |
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* <assertion> ::= <identifier> <operator> <literal> |
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* <concatenation> ::= <statement> { <logic> <statement> } |
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* <group> ::= "(" <concatenation> ")" |
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* <statement> ::= <assertion> | <group> |
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* <query> ::= <concatenation> |
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* |
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*/ |
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private $tokenIndex; |
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private $tokenStream = []; |
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public function __construct() |
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{ |
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$this->tokenIndex = -1; |
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} |
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/** |
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* Lex, initialise and return the AST. |
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* |
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* @param $string |
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* |
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* @return bool|ASTAssertion|ASTGroup |
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*/ |
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public function parse($string) |
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{ |
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$this->tokenStream = Lexer::lex($string); |
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$this->tokenIndex = -1; |
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return $this->getAST(); |
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} |
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/** |
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* Entry point of the grammar parsing. |
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* |
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* @return bool|ASTAssertion|ASTGroup |
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*/ |
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public function getAST() |
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{ |
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// The top-level syntax is, in general, a concatenation of statements with logic connectors. |
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$concatenation = $this->matchConcatenation(); |
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// Make sure we are at the end of the UQL |
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$token = $this->nextToken(); |
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if ($token === false) { |
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return $concatenation; |
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} |
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$this->throwUnexpectedTokenSyntaxError(['LOGIC'], "Logic operator or end of UQL expected after statement in first-level concatenation"); |
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} |
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/** |
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* Tries to match the following tokens to a <concatenation> grammar. |
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* |
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* @return bool|ASTAssertion|ASTGroup |
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*/ |
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public function matchConcatenation() |
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{ |
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$elements = []; |
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$firstStatement = $this->matchStatement(); |
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if ($firstStatement === false) { |
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$this->throwUnexpectedTokenSyntaxError(['IDENTIFIER', 'GROUP_START'], 'Expected statement at beginning of concatenation.'); |
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} |
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$elements[] = $firstStatement; |
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$firstLogic = $this->matchLogic(); |
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if ($firstLogic === false) { |
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// There is no actual concatenation. This is a single statement. Return as such. |
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return $firstStatement; |
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} |
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$logic = $firstLogic; |
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// While there are concatenating logic operators, keep adding elements. |
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while ($logic !== false) { |
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if ($logic['token'] != $firstLogic['token']) { |
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$this->throwSyntaxError('Can\'t mix ORs and ANDs in same-level expression, ambiguous statement.'); |
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} |
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$statement = $this->matchStatement(); |
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if ($statement === false) { |
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$this->throwUnexpectedTokenSyntaxError(['IDENTIFIER', 'GROUP_START'], 'Expected statement after logic operator'); |
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} |
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$elements[] = $statement; |
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$logic = $this->matchLogic(); |
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} |
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return new ASTGroup($firstLogic['token'], $elements); |
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} |
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/** |
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* Tries to match a general <statement>, that is a <group> or <assertion> |
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* |
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* @return bool|ASTAssertion|ASTGroup |
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*/ |
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public function matchStatement() |
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{ |
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// Try <group> |
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$matchGroup = $this->matchGroup(); |
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if ($matchGroup !== false) { |
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return $matchGroup; |
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} |
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// Try <assertion> |
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$matchAssertion = $this->matchAssertion(); |
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if ($matchAssertion !== false) { |
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return $matchAssertion; |
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} |
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// None found |
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$this->rewindToken(); |
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return false; |
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} |
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/** |
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* Tries to match a <group> grammar to the following tokens |
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* |
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* @return bool|ASTAssertion|ASTGroup |
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*/ |
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public function matchGroup() |
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{ |
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$token = $this->nextToken(); |
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// Check for the open parenthesis |
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if ($token['token'] != "T_BRACKET_OPEN") { |
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$this->rewindToken(); |
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return false; |
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} |
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// The interior of a group is a <concatenation> |
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$concatenation = $this->matchConcatenation(); |
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$token = $this->nextToken(); |
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// Check for closed parenthesis. Mismatch is a Syntax Error. |
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if ($token['token'] != "T_BRACKET_CLOSE") { |
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$this->throwUnexpectedTokenSyntaxError(['GROUP_END'], 'Expected closing bracket.'); |
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} |
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return $concatenation; |
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} |
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/** |
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* Tries to match the following tokens to an <assertion>. |
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* |
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* @throws Exception\UQLSyntaxError |
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* @return bool|ASTAssertion |
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*/ |
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public function matchAssertion() |
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{ |
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$identifier = $this->nextToken(); |
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if ($identifier['token'] != 'T_IDENTIFIER') { |
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// If a stream doesn't start with an identifier, it's not an <assertion>. |
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$this->rewindToken(); |
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return false; |
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} |
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$operator = $this->matchOperator(); |
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if ($operator === false) { |
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$this->nextToken(); // MatchOperator rewinds |
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$this->throwUnexpectedTokenSyntaxError(['OPERATOR'], 'Comparison operator expected after identifier'); |
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} |
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$array = $this->matchArray(); |
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if ($array) { |
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if (!in_array($operator['token'], ['T_OP_IN', 'T_OP_NIN'])) { |
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throw new UQLSyntaxError("Arrays are only valid after IN or NOT IN operators"); |
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} |
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return new ASTAssertion($identifier['match'], $operator['token'], $array); |
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} |
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$literal = $this->nextToken(); |
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if ($literal['token'] == 'T_FUNCTION_CALL') { |
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return new ASTAssertion($identifier['match'], $operator['token'], ASTFunctionCall::createFromExpression($literal['match'])); |
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} |
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if (strpos($literal['token'], 'T_LITERAL') !== 0) { |
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$this->throwUnexpectedTokenSyntaxError(['ARRAY_START', 'LITERAL'], 'Array, value or function call expected after comparison operator'); |
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} |
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$literal = $this->transformLiteral($literal); |
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return new ASTAssertion($identifier['match'], $operator['token'], $literal['match']); |
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} |
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/** |
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* Tries to match the next token to an <operator>. |
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* |
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* @return bool |
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*/ |
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public function matchOperator() |
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{ |
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$operator = $this->nextToken(); |
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switch ($operator['token']) { |
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case 'T_OP_NEQ': |
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case 'T_OP_LTE': |
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case 'T_OP_LT': |
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case 'T_OP_GTE': |
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case 'T_OP_GT': |
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case 'T_OP_EQ': |
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case 'T_OP_LIKE': |
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case 'T_OP_IN': |
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case 'T_OP_NIN': |
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return $operator; |
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break; |
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default: |
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$this->rewindToken(); |
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return false; |
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} |
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} |
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public function matchArray() |
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{ |
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$token = $this->nextToken(); |
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if ($token['token'] != "T_ARRAY_OPEN") { |
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$this->rewindToken(); |
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return false; |
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} |
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$element = $this->nextToken(); |
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if ($element['token'] == "T_ARRAY_CLOSE") { |
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// Empty array |
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return new ASTArray(); |
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} |
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$elements = [$element['match']]; |
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$comma = $this->nextToken(); |
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while ($comma['token'] == "T_ARRAY_SEPARATOR") { |
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$element = $this->nextToken(); |
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if ($element['token'] !== 'T_LITERAL') { |
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$this->throwUnexpectedTokenSyntaxError(['LITERAL'], "An array must consist of literals"); |
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} |
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$elements[] = $element['match']; |
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$comma = $this->nextToken(); |
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} |
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if ($comma['token'] != 'T_ARRAY_CLOSE') { |
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// Unterminated array |
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$this->throwUnexpectedTokenSyntaxError(['ARRAY_END'], "An array must end with ']'."); |
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} |
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return new ASTArray($elements); |
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} |
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285
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/** |
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* Tries to match the next token to a <logic> operator |
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* |
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* @return bool |
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*/ |
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public function matchLogic() |
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{ |
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$token = $this->nextToken(); |
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if ($token['token'] == 'T_LOGIC_AND' || $token['token'] == 'T_LOGIC_OR' || $token['token'] == 'T_LOGIC_XOR') { |
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return $token; |
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} |
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// None found |
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$this->rewindToken(); |
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return false; |
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} |
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/** |
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* @return mixed |
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306
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*/ |
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public function getTokenStream() |
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308
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{ |
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return $this->tokenStream; |
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} |
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/** |
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* @param mixed $tokenStream |
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314
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*/ |
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315
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public function setTokenStream($tokenStream) |
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316
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{ |
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$this->tokenStream = $tokenStream; |
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318
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} |
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319
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320
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/** |
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321
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* @return mixed |
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322
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*/ |
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323
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public function getTokenIndex() |
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324
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{ |
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325
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return $this->tokenIndex; |
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326
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} |
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327
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328
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/** |
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329
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* @param mixed $tokenIndex |
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330
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*/ |
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331
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public function setTokenIndex($tokenIndex) |
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332
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{ |
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333
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$this->tokenIndex = $tokenIndex; |
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334
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} |
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335
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336
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|
|
/** |
|
337
|
|
|
* Advance the token index and return. |
|
338
|
|
|
* |
|
339
|
|
|
* @return bool |
|
340
|
|
|
*/ |
|
341
|
|
|
private function nextToken() |
|
342
|
|
|
{ |
|
343
|
|
|
$this->tokenIndex++; |
|
344
|
|
|
|
|
345
|
|
|
return $this->currentToken(); |
|
346
|
|
|
} |
|
347
|
|
|
|
|
348
|
|
|
/** |
|
349
|
|
|
* Return the current token, without advancing the index. |
|
350
|
|
|
* |
|
351
|
|
|
* @return bool |
|
352
|
|
|
*/ |
|
353
|
|
|
private function currentToken() |
|
354
|
|
|
{ |
|
355
|
|
|
return isset($this->tokenStream[$this->tokenIndex]) ? $this->tokenStream[$this->tokenIndex] : false; |
|
356
|
|
|
} |
|
357
|
|
|
|
|
358
|
|
|
/** |
|
359
|
|
|
* Move back the token index once. |
|
360
|
|
|
*/ |
|
361
|
|
|
private function rewindToken() |
|
362
|
|
|
{ |
|
363
|
|
|
$this->tokenIndex--; |
|
364
|
|
|
} |
|
365
|
|
|
|
|
366
|
|
|
/** |
|
367
|
|
|
* Helper method. Throws an Exception representing a Syntax Error. |
|
368
|
|
|
* |
|
369
|
|
|
* @param $message |
|
370
|
|
|
* |
|
371
|
|
|
* @throws \Exception |
|
372
|
|
|
*/ |
|
373
|
|
|
private function throwUnexpectedTokenSyntaxError(array $expectedTokenCategories, $message = null) |
|
374
|
|
|
{ |
|
375
|
|
|
$parsedTokenStream = array_slice($this->tokenStream, 0, $this->tokenIndex + 1); |
|
376
|
|
|
if ($this->currentToken() === false) { |
|
377
|
|
|
throw new UqlUnexpectedEndOfExpressionException( |
|
378
|
|
|
$expectedTokenCategories, |
|
379
|
|
|
$parsedTokenStream, |
|
380
|
|
|
$message); |
|
381
|
|
|
} |
|
382
|
|
|
throw new UqlUnexpectedTokenException( |
|
383
|
|
|
$this->currentToken()['token'], |
|
384
|
|
|
$this->currentToken()['match'], |
|
385
|
|
|
$expectedTokenCategories, |
|
386
|
|
|
$parsedTokenStream, |
|
387
|
|
|
$message |
|
388
|
|
|
); |
|
389
|
|
|
} |
|
390
|
|
|
|
|
391
|
|
|
private function throwSyntaxError($message) |
|
392
|
|
|
{ |
|
393
|
|
|
throw new UQLSyntaxError('Syntax error: ' . $message); |
|
394
|
|
|
} |
|
395
|
|
|
|
|
396
|
|
|
/** |
|
397
|
|
|
* Transforms a literal subtype (e.g. T_LITERAL_FALSE) into a plain |
|
398
|
|
|
* literal match. Plain literals are unchanged. |
|
399
|
|
|
* |
|
400
|
|
|
* @param $literal |
|
401
|
|
|
* |
|
402
|
|
|
* @return array |
|
403
|
|
|
*/ |
|
404
|
|
|
private function transformLiteral($literal) |
|
405
|
|
|
{ |
|
406
|
|
|
switch ($literal['token']) { |
|
407
|
|
|
case 'T_LITERAL_FALSE': |
|
408
|
|
|
$match = false; |
|
409
|
|
|
break; |
|
410
|
|
|
case 'T_LITERAL_TRUE': |
|
411
|
|
|
$match = true; |
|
412
|
|
|
break; |
|
413
|
|
|
case 'T_LITERAL_EMPTY': |
|
414
|
|
|
$match = null; |
|
415
|
|
|
break; |
|
416
|
|
|
default: |
|
417
|
|
|
$match = $literal['match']; |
|
418
|
|
|
} |
|
419
|
|
|
|
|
420
|
|
|
return [ |
|
421
|
|
|
'token' => 'T_LITERAL', |
|
422
|
|
|
'match' => $match |
|
423
|
|
|
]; |
|
424
|
|
|
} |
|
425
|
|
|
} |
|
426
|
|
|
|
The break statement is not necessary if it is preceded for example by a return statement:
If you would like to keep this construct to be consistent with other case statements, you can safely mark this issue as a false-positive.