1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
|
/*
An alternative implementation of "strtod()" that is both
simplier, and thread-safe.
From mit-threads as bundled with MySQL 3.23
SQL:2003 specifies a number as
<signed numeric literal> ::= [ <sign> ] <unsigned numeric literal>
<unsigned numeric literal> ::=
<exact numeric literal>
| <approximate numeric literal>
<exact numeric literal> ::=
<unsigned integer> [ <period> [ <unsigned integer> ] ]
| <period> <unsigned integer>
<approximate numeric literal> ::= <mantissa> E <exponent>
<mantissa> ::= <exact numeric literal>
<exponent> ::= <signed integer>
So do we.
*/
#include "my_base.h" /* Includes errno.h */
#include "m_ctype.h"
static double scaler10[] = {
1.0, 1e10, 1e20, 1e30, 1e40, 1e50, 1e60, 1e70, 1e80, 1e90
};
static double scaler1[] = {
1.0, 10.0, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9
};
double my_strtod(const char *str, char **end)
{
double result= 0.0;
int negative, ndigits;
const char *old_str;
my_bool overflow=0;
while (my_isspace(&my_charset_latin1, *str))
str++;
if ((negative= (*str == '-')) || *str=='+')
str++;
old_str= str;
while (my_isdigit (&my_charset_latin1, *str))
{
result= result*10.0 + (*str - '0');
str++;
}
ndigits= str-old_str;
if (*str == '.')
{
double p10=10;
str++;
old_str= str;
while (my_isdigit (&my_charset_latin1, *str))
{
result+= (*str++ - '0')/p10;
p10*=10;
}
ndigits+= str-old_str;
if (!ndigits) str--;
}
if (ndigits && (*str=='e' || *str=='E'))
{
int exp= 0;
int neg= 0;
const char *old_str= str++;
if ((neg= (*str == '-')) || *str == '+')
str++;
if (!my_isdigit (&my_charset_latin1, *str))
str= old_str;
else
{
double scaler= 1.0;
while (my_isdigit (&my_charset_latin1, *str))
{
if (exp < 9999) /* protection against exp overflow */
exp= exp*10 + *str - '0';
str++;
}
if (exp >= 1000)
{
if (neg)
result= 0.0;
else
overflow= 1;
goto done;
}
while (exp >= 100)
{
scaler*= 1.0e100;
exp-= 100;
}
scaler*= scaler10[exp/10]*scaler1[exp%10];
if (neg)
result/= scaler;
else
result*= scaler;
}
}
done:
if (end)
*end = (char *)str;
if (overflow || isinf(result))
{
result= DBL_MAX;
errno= EOVERFLOW;
}
return negative ? -result : result;
}
double my_atof(const char *nptr)
{
return (my_strtod(nptr, 0));
}
|
