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129 lines
3.0 KiB
C++
129 lines
3.0 KiB
C++
#include <DB/Parsers/CommonParsers.h>
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#include <DB/Parsers/ParserSampleRatio.h>
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#include <DB/Parsers/ASTSampleRatio.h>
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#include <DB/IO/ReadHelpers.h>
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namespace DB
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{
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static bool parseDecimal(IParser::Pos & pos, IParser::Pos end, ASTSampleRatio::Rational & res, IParser::Pos & max_parsed_pos)
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{
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ParserWhiteSpaceOrComments ws;
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ws.ignore(pos, end);
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UInt64 num_before = 0;
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UInt64 num_after = 0;
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Int64 exponent = 0;
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IParser::Pos pos_after_first_num = tryReadIntText(num_before, pos, end);
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bool has_num_before_point = pos_after_first_num > pos;
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pos = pos_after_first_num;
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bool has_point = pos < end && *pos == '.';
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if (has_point)
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++pos;
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if (!has_num_before_point && !has_point)
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return false;
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size_t number_of_digits_after_point = 0;
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if (has_point)
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{
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IParser::Pos pos_after_second_num = tryReadIntText(num_after, pos, end);
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number_of_digits_after_point = pos_after_second_num - pos;
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pos = pos_after_second_num;
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}
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bool has_exponent = pos < end && (*pos == 'e' || *pos == 'E');
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if (has_exponent)
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{
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++pos;
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IParser::Pos pos_after_exponent = tryReadIntText(exponent, pos, end);
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if (pos_after_exponent == pos)
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return false;
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pos = pos_after_exponent;
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}
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res.numerator = num_before * exp10(number_of_digits_after_point) + num_after;
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res.denominator = exp10(number_of_digits_after_point);
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if (exponent > 0)
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res.numerator *= exp10(exponent);
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if (exponent < 0)
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res.denominator *= exp10(-exponent);
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/// NOTE Удаление общих степеней десяти из числителя и знаменателя - не нужно.
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return true;
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}
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/** Возможные варианты:
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*
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* 12345
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* - целое число
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*
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* 0.12345
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* .12345
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* 0.
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* - дробь в обычной десятичной записи
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*
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* 1.23e-1
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* - дробь в инженерной десятичной записи
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*
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* 123 / 456
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* - дробь с произвольным знаменателем
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*
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* На всякий случай, в числителе и знаменателе дроби, поддерживаем предыдущие случаи.
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* Пример:
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* 123.0 / 456e0
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*/
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bool ParserSampleRatio::parseImpl(IParser::Pos & pos, IParser::Pos end, ASTPtr & node, IParser::Pos & max_parsed_pos, Expected & expected)
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{
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auto begin = pos;
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ParserWhiteSpaceOrComments ws;
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ASTSampleRatio::Rational numerator;
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ASTSampleRatio::Rational denominator;
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ASTSampleRatio::Rational res;
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ws.ignore(pos, end);
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if (!parseDecimal(pos, end, numerator, max_parsed_pos))
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return false;
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ws.ignore(pos, end);
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bool has_slash = pos < end && *pos == '/';
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if (has_slash)
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{
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++pos;
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ws.ignore(pos, end);
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if (!parseDecimal(pos, end, denominator, max_parsed_pos))
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return false;
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res.numerator = numerator.numerator * denominator.denominator;
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res.denominator = numerator.denominator * denominator.numerator;
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}
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else
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{
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res = numerator;
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}
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ws.ignore(pos, end);
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node = new ASTSampleRatio(StringRange(begin, pos), res);
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return true;
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}
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}
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