ClickHouse/dbms/include/DB/Parsers/CommonParsers.h

#ifndef DBMS_PARSERS_COMMONPARSERS_H
#define DBMS_PARSERS_COMMONPARSERS_H

#include <cstring>

#include <DB/Parsers/IParserBase.h>


namespace DB
{

using Poco::SharedPtr;


/** если прямо сейчас не s, то ошибка
  */
class ParserString : public IParserBase
{
private:
	String s;
public:
	ParserString(const String & s_) : s(s_) {}
protected:
	String getName() { return s; }

	bool parseImpl(Pos & pos, Pos end, ASTPtr & node, String & expected)
	{
		if (static_cast<ssize_t>(s.size()) > end - pos || std::strncmp(pos, s.data(), s.size()))
			return false;
		else
		{
			pos += s.size();
 			return true;
 		}
	}
};

	
/** если сейчас словарный символ - то ошибка
  * понимается только латиница
  */
class ParserNotWordCharOrEnd : public IParserBase
{
protected:
	String getName() { return "non-word character"; }

	bool parseImpl(Pos & pos, Pos end, ASTPtr & node, String & expected)
	{
		if (pos == end)
			return true;

		if ((*pos >= 'a' && *pos <= 'z') || (*pos >= 'A' && *pos <= 'Z') || (*pos >= '0' && *pos <= '9') || *pos == '_')
			return false;

		++pos;
		return true;
	}
};


/** пробельные символы
  */
class ParserWhiteSpace : public IParserBase
{
protected:
	String getName() { return "white space"; }

	bool parseImpl(Pos & pos, Pos end, ASTPtr & node, String & expected)
	{
		Pos begin = pos;
		while (*pos == ' ' || *pos == '\t' || *pos == '\n' || *pos == '\r' || *pos == '\f')
			++pos;

		return pos != begin;
	}
};


class ParserCStyleComment : public IParserBase
{
protected:
	String getName() { return "C-style comment"; }

	bool parseImpl(Pos & pos, Pos end, ASTPtr & node, String & expected)
	{
		if (end - pos >= 4 && pos[0] == '/' && pos[1] == '*')
		{
			pos += 2;
			while (end - pos >= 2 && pos[0] != '*' && pos[1] != '/')
				++pos;

			if (end - pos < 2)
			{
				expected = "closing of C-style comment '*/'";
				return false;
			}
			else
			{
				pos += 2;
				return true;
			}
		}
		else
			return false;
	}
};


class ParserSQLStyleComment : public IParserBase
{
protected:
	String getName() { return "SQL-style comment"; }

	bool parseImpl(Pos & pos, Pos end, ASTPtr & node, String & expected)
	{
		if (end - pos >= 2 && pos[0] == '-' && pos[1] == '-')
		{
			pos += 2;
			while (pos != end && *pos != '\n')
				++pos;

			if (pos != end)
				++pos;
			return true;
		}
		else
			return false;
	}
};


/** комментарии '--' или c-style
  */
class ParserComment : public IParserBase
{
protected:
	String getName() { return "comment"; }

	bool parseImpl(Pos & pos, Pos end, ASTPtr & node, String & expected)
	{
		ParserCStyleComment p1;
		ParserSQLStyleComment p2;
	
		return p1.ignore(pos, end, expected)
			|| p2.ignore(pos, end, expected);
	}
};


class ParserWhiteSpaceOrComments : public IParserBase
{
protected:
	String getName() { return "white space or comments"; }

	bool parseImpl(Pos & pos, Pos end, ASTPtr & node, String & expected)
	{
		ParserWhiteSpace p1;
		ParserComment p2;
	
		bool res = false;
		while (p1.ignore(pos, end, expected) || p2.ignore(pos, end, expected))
			res = true;
		return res;
	}
};

}

#endif