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//
// strtod.c
//
// Convert string to double
//
// Copyright (C) 2002 Michael Ringgaard. 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 <math.h>
#include <float.h>
#include <stdlib.h>
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;
// 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 HUGE_VAL;
}
// 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 (number == HUGE_VAL) errno = ERANGE;
if (endptr) *endptr = p;
return number;
}
float strtof(const char *str, char **endptr) {
return (float) strtod(str, endptr);
}
long double strtold(const char *str, char **endptr) {
return strtod(str, endptr);
}
double atof(const char *str) {
return strtod(str, NULL);
}