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125 lines
2.4 KiB
C
125 lines
2.4 KiB
C
/*
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An alternative implementation of "strtod()" that is both
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simplier, and thread-safe.
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From mit-threads as bundled with MySQL 3.22
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SQL:2003 specifies a number as
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<signed numeric literal> ::= [ <sign> ] <unsigned numeric literal>
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<unsigned numeric literal> ::=
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<exact numeric literal>
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| <approximate numeric literal>
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<exact numeric literal> ::=
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<unsigned integer> [ <period> [ <unsigned integer> ] ]
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| <period> <unsigned integer>
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<approximate numeric literal> ::= <mantissa> E <exponent>
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<mantissa> ::= <exact numeric literal>
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<exponent> ::= <signed integer>
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So do we.
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*/
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#include "my_base.h"
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#include "m_ctype.h"
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static double scaler10[] = {
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1.0, 1e10, 1e20, 1e30, 1e40, 1e50, 1e60, 1e70, 1e80, 1e90
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};
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static double scaler1[] = {
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1.0, 10.0, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9
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};
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#ifndef HUGE_VAL /* Should be +Infinitive */
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#define HUGE_VAL DBL_MAX
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#endif
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double my_strtod(const char *str, char **end)
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{
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double result= 0.0;
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int negative, ndigits;
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const char *old_str;
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while (my_isspace(&my_charset_latin1, *str))
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str++;
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if ((negative= (*str == '-')) || *str=='+')
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str++;
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old_str= str;
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while (my_isdigit (&my_charset_latin1, *str))
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{
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result= result*10.0 + (*str - '0');
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str++;
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}
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ndigits= str-old_str;
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if (*str == '.')
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{
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double p10=10;
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str++;
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old_str= str;
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while (my_isdigit (&my_charset_latin1, *str))
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{
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result+= (*str++ - '0')/p10;
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p10*=10;
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}
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ndigits+= str-old_str;
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if (!ndigits) str--;
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}
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if (ndigits && (*str=='e' || *str=='E'))
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{
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int exp= 0;
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int neg= 0;
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const char *old_str= str++;
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if ((neg= (*str == '-')) || *str == '+')
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str++;
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if (!my_isdigit (&my_charset_latin1, *str))
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str= old_str;
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else
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{
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double scaler= 1.0;
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while (my_isdigit (&my_charset_latin1, *str))
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{
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exp= exp*10 + *str - '0';
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str++;
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}
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if (exp >= 1000)
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{
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result= neg ? 0.0 : HUGE_VAL;
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goto done;
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}
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while (exp >= 100)
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{
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scaler*= 1.0e100;
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exp-= 100;
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}
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scaler*= scaler10[exp/10]*scaler1[exp%10];
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if (neg)
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result/= scaler;
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else
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result*= scaler;
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}
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}
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done:
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if (end)
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*end = (char *)str;
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return negative ? -result : result;
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}
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double my_atof(const char *nptr)
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{
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return (my_strtod(nptr, 0));
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}
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