1#include <Common/intExp.h>
2
3#include <Parsers/CommonParsers.h>
4#include <Parsers/ParserSampleRatio.h>
5#include <Parsers/ASTSampleRatio.h>
6#include <IO/ReadHelpers.h>
7
8
9namespace DB
10{
11
12
13static bool parseDecimal(const char * pos, const char * end, ASTSampleRatio::Rational & res)
14{
15 UInt64 num_before = 0;
16 UInt64 num_after = 0;
17 Int64 exponent = 0;
18
19 const char * pos_after_first_num = tryReadIntText(num_before, pos, end);
20
21 bool has_num_before_point = pos_after_first_num > pos;
22 pos = pos_after_first_num;
23 bool has_point = pos < end && *pos == '.';
24
25 if (has_point)
26 ++pos;
27
28 if (!has_num_before_point && !has_point)
29 return false;
30
31 size_t number_of_digits_after_point = 0;
32
33 if (has_point)
34 {
35 const char * pos_after_second_num = tryReadIntText(num_after, pos, end);
36 number_of_digits_after_point = pos_after_second_num - pos;
37 pos = pos_after_second_num;
38 }
39
40 bool has_exponent = pos < end && (*pos == 'e' || *pos == 'E');
41
42 if (has_exponent)
43 {
44 ++pos;
45 const char * pos_after_exponent = tryReadIntText(exponent, pos, end);
46
47 if (pos_after_exponent == pos)
48 return false;
49 }
50
51 res.numerator = num_before * intExp10(number_of_digits_after_point) + num_after;
52 res.denominator = intExp10(number_of_digits_after_point);
53
54 if (exponent > 0)
55 res.numerator *= intExp10(exponent);
56 if (exponent < 0)
57 res.denominator *= intExp10(-exponent);
58
59 /// NOTE You do not need to remove the common power of ten from the numerator and denominator.
60 return true;
61}
62
63
64/** Possible options:
65 *
66 * 12345
67 * - an integer
68 *
69 * 0.12345
70 * .12345
71 * 0.
72 * - fraction in ordinary decimal notation
73 *
74 * 1.23e-1
75 * - fraction in scientific decimal notation
76 *
77 * 123 / 456
78 * - fraction with an ordinary denominator
79 *
80 * Just in case, in the numerator and denominator of the fraction, we support the previous cases.
81 * Example:
82 * 123.0 / 456e0
83 */
84bool ParserSampleRatio::parseImpl(Pos & pos, ASTPtr & node, Expected &)
85{
86 ASTSampleRatio::Rational numerator;
87 ASTSampleRatio::Rational denominator;
88 ASTSampleRatio::Rational res;
89
90 if (!parseDecimal(pos->begin, pos->end, numerator))
91 return false;
92 ++pos;
93
94 bool has_slash = pos->type == TokenType::Slash;
95
96 if (has_slash)
97 {
98 ++pos;
99
100 if (!parseDecimal(pos->begin, pos->end, denominator))
101 return false;
102 ++pos;
103
104 res.numerator = numerator.numerator * denominator.denominator;
105 res.denominator = numerator.denominator * denominator.numerator;
106 }
107 else
108 {
109 res = numerator;
110 }
111
112 node = std::make_shared<ASTSampleRatio>(res);
113 return true;
114}
115
116}
117