72 lines
1.7 KiB
C++
72 lines
1.7 KiB
C++
#ifndef SQLPARSER_H
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#define SQLPARSER_H
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#include "SqlLexer.h"
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#include <memory>
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#include <optional>
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enum class Keyword {
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NotAKeyword,
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As,
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By,
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Delete,
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From,
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Group,
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Insert,
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Order,
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Select,
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Update,
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Where,
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};
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namespace SqlAst {
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class Select;
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class SelectList;
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}
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// The parsing works by calling functions that know either a global part
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// or a smaller specific part and is thus recursive. At certain points a function parsing something specific
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// will reach a point where it is in a valid terminal state and it encounters something that cannot be a continuation
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// of what it is parsing and thus returns succesfully or it is in a non terminal state and encounters something unexpected
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// In both cases it will return hoping that one of the functions above can continue (and recover from the error if needed)
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class SqlParser
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{
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public:
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explicit SqlParser(SqlLexer &lexer);
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void parse();
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/** Checks to see if the next token is the expected keyword.
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*
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* If it is the token is consumed and the function returns true.
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* Otherwise false is returned
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*/
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std::optional<SqlToken> expectKeyword(Keyword kw);
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std::optional<SqlToken> expectSymbol();
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std::optional<SqlToken> expectToken(BasicTokenType tt);
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/** If the next token is Keyword kw consume it otherwise do nothing.
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* In some cases the return value is unimportant as the keyword is completely optional
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* in other cases the optional keywords presence might force the next token to be something specific
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*
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* \return true if the token was found
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*/
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bool consumeOptionalKeyword(Keyword kw);
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private:
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//using TokenStack = std::stack<SqlToken>;
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//TokenStack tokenStack;
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SqlLexer &lexer;
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//bool try_reduce(SqkToken token);
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};
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#endif // SQLPARSER_H
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