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53 lines
2.1 KiB
53 lines
2.1 KiB
Introduction
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============
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Doctrine Lexer is a library that can be used in Top-Down, Recursive
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Descent Parsers. This lexer is used in Doctrine Annotations and in
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Doctrine ORM (DQL).
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To write your own parser you just need to extend ``Doctrine\Common\Lexer\AbstractLexer``
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and implement the following three abstract methods.
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.. code-block:: php
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/**
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* Lexical catchable patterns.
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*
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* @return array
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*/
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abstract protected function getCatchablePatterns();
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/**
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* Lexical non-catchable patterns.
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*
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* @return array
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*/
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abstract protected function getNonCatchablePatterns();
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/**
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* Retrieve token type. Also processes the token value if necessary.
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*
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* @param string $value
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* @return integer
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*/
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abstract protected function getType(&$value);
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These methods define the `lexical <http://en.wikipedia.org/wiki/Lexical_analysis>`_
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catchable and non-catchable patterns and a method for returning the
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type of a token and filtering the value if necessary.
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The Lexer is responsible for giving you an API to walk across a
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string one character at a time and analyze the type of each character, value and position of
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each token in the string. The low level API of the lexer is pretty simple:
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- ``setInput($input)`` - Sets the input data to be tokenized. The Lexer is immediately reset and the new input tokenized.
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- ``reset()`` - Resets the lexer.
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- ``resetPeek()`` - Resets the peek pointer to 0.
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- ``resetPosition($position = 0)`` - Resets the lexer position on the input to the given position.
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- ``isNextToken($token)`` - Checks whether a given token matches the current lookahead.
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- ``isNextTokenAny(array $tokens)`` - Checks whether any of the given tokens matches the current lookahead.
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- ``moveNext()`` - Moves to the next token in the input string.
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- ``skipUntil($type)`` - Tells the lexer to skip input tokens until it sees a token with the given value.
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- ``isA($value, $token)`` - Checks if given value is identical to the given token.
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- ``peek()`` - Moves the lookahead token forward.
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- ``glimpse()`` - Peeks at the next token, returns it and immediately resets the peek.
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