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/*
An alternative implementation of "strtod()" that is both
simplier, and thread-safe.
From mit-threads as bundled with MySQL 3.22
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"
#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
};
// let's use a static array for not to accumulate the error
static double pastpoint[] = {
1e-1, 1e-2, 1e-3, 1e-4, 1e-5, 1e-6, 1e-7, 1e-8, 1e-9,
1e-10, 1e-11, 1e-12, 1e-13, 1e-14, 1e-15, 1e-16, 1e-17, 1e-18, 1e-19,
1e-20, 1e-21, 1e-22, 1e-23, 1e-24, 1e-25, 1e-26, 1e-27, 1e-28, 1e-29,
1e-30, 1e-31, 1e-32, 1e-33, 1e-34, 1e-35, 1e-36, 1e-37, 1e-38, 1e-39,
1e-40, 1e-41, 1e-42, 1e-43, 1e-44, 1e-45, 1e-46, 1e-47, 1e-48, 1e-49,
1e-50, 1e-51, 1e-52, 1e-53, 1e-54, 1e-55, 1e-56, 1e-57, 1e-58, 1e-59,
};
double my_strtod(const char *str, char **end)
{
double result= 0.0;
int negative, ndigits;
const char *old_str;
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 == '.')
{
int n= 0;
str++;
old_str= str;
while (my_isdigit (&my_charset_latin1, *str))
{
if (n < sizeof(pastpoint)/sizeof(pastpoint[0]))
{
result+= pastpoint[n] * (*str - '0');
n++;
}
str++;
}
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))
{
exp= exp*10 + *str - '0';
str++;
}
if (exp >= 1000)
{
if (neg)
result= 0.0;
else
result= DBL_MAX;
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 (isinf(result))
result=DBL_MAX;
return negative ? -result : result;
}
double my_atof(const char *nptr)
{
return (strtod(nptr, 0));
}
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