/*
* strtod.c
*
* Convert string to double
*
* Copyright (C) 2002 Michael Ringgaard. All rights reserved.
* Copyright 2006-2008 H. Peter Anvin - All Rights Reserved
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the project nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <errno.h>
#include <ctype.h>
#include <stdlib.h>
#include <math.h>
static inline int is_real(double x)
{
const double Inf = 1.0 / 0.0;
return (x < Inf) && (x >= -Inf);
}
double strtod(const char *str, char **endptr)
{
double number;
int exponent;
int negative;
char *p = (char *)str;
double p10;
int n;
int num_digits;
int num_decimals;
const double Inf = 1.0 / 0.0;
// Skip leading whitespace
while (isspace(*p))
p++;
// Handle optional sign
negative = 0;
switch (*p) {
case '-':
negative = 1; // Fall through to increment position
case '+':
p++;
}
number = 0.;
exponent = 0;
num_digits = 0;
num_decimals = 0;
// Process string of digits
while (isdigit(*p)) {
number = number * 10. + (*p - '0');
p++;
num_digits++;
}
// Process decimal part
if (*p == '.') {
p++;
while (isdigit(*p)) {
number = number * 10. + (*p - '0');
p++;
num_digits++;
num_decimals++;
}
exponent -= num_decimals;
}
if (num_digits == 0) {
errno = ERANGE;
return 0.0;
}
// Correct for sign
if (negative)
number = -number;
// Process an exponent string
if (*p == 'e' || *p == 'E') {
// Handle optional sign
negative = 0;
switch (*++p) {
case '-':
negative = 1; // Fall through to increment pos
case '+':
p++;
}
// Process string of digits
n = 0;
while (isdigit(*p)) {
n = n * 10 + (*p - '0');
p++;
}
if (negative)
exponent -= n;
else
exponent += n;
}
if (exponent < __DBL_MIN_EXP__ || exponent > __DBL_MAX_EXP__) {
errno = ERANGE;
return Inf;
}
// Scale the result
p10 = 10.;
n = exponent;
if (n < 0)
n = -n;
while (n) {
if (n & 1) {
if (exponent < 0)
number /= p10;
else
number *= p10;
}
n >>= 1;
p10 *= p10;
}
if (!is_real(number))
errno = ERANGE;
if (endptr)
*endptr = p;
return number;
}
