98 lines
2 KiB
C++
98 lines
2 KiB
C++
#include "SqlParser.h"
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#include "SqlAstSelect.h"
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#include <stdexcept>
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#include <unordered_map>
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using namespace SqlAst;
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Keyword isKeyword(const QString &symbol)
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{
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static std::unordered_map<std::string, Keyword> lookup_map = {
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{ "as", Keyword::As },
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{ "by", Keyword::By },
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{ "delete", Keyword::Delete },
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{ "from", Keyword::From },
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{ "group", Keyword::Group },
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{ "insert", Keyword::Insert },
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{ "order", Keyword::Order },
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{ "select", Keyword::Select },
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{ "update", Keyword::Update },
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{ "where", Keyword::Where }
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};
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auto res = lookup_map.find(symbol.toLower().toUtf8().data());
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if (res != lookup_map.end())
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return res->second;
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return Keyword::NotAKeyword;
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}
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/*
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Put tokens on a stack
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Every time something is put on the stack see if it matches a rule
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The stack needs to contain both tokens from the lexical analyzer as tokens for reductions done by the parser.
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Matching rules, as we need to match against the top of the stack we should match the rules end to start.
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Meaning if we have on the stack A B C then we need to consider rules ending with a C
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*/
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class StackItem {
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public:
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int Token;
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};
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SqlParser::SqlParser(SqlLexer &lexer)
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: lexer(lexer)
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{
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}
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std::shared_ptr<SqlAst::Node> SqlParser::parse()
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{
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// Basic algo:
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// LOOP
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// GET token
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// IF NOT try_reduce(token)
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// THEN SHIFT
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// END LOOP
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std::shared_ptr<SqlAst::Node> result;
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while (true) {
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SqlToken token = lexer.nextBasicToken();
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if (token.ok) {
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if (token.tokenType == BasicTokenType::Symbol) {
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Keyword kw = isKeyword(token.out);
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switch (kw) {
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case Keyword::Select:
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parseSelect(*this);
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break;
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case Keyword::NotAKeyword:
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default:
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// unexpected
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break;
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}
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}
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else if (token.tokenType == BasicTokenType::End) {
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// Are we at the top level?
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return result;
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}
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}
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else {
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// error during lexical analysis, need to recover
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throw std::runtime_error("Unrecognized input");
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}
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}
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}
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//bool try_reduce(SqkToken token)
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//{
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// // what state are we in? what are we expecting
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//}
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