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| -rw-r--r-- | lib/strtod.c | 202 |
1 files changed, 202 insertions, 0 deletions
diff --git a/lib/strtod.c b/lib/strtod.c new file mode 100644 index 00000000..10edb5cf --- /dev/null +++ b/lib/strtod.c @@ -0,0 +1,202 @@ +/* Copyright (C) 1991, 1992, 1997, 1999 Free Software Foundation, Inc. + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 2, or (at your option) + any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program; if not, write to the Free Software Foundation, + Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ + +#if HAVE_CONFIG_H +# include <config.h> +#endif + +#include <errno.h> +#ifndef errno +extern int errno; +#endif + +#include <ctype.h> + +#if defined (STDC_HEADERS) || (!defined (isascii) && !defined (HAVE_ISASCII)) +# define IN_CTYPE_DOMAIN(c) 1 +#else +# define IN_CTYPE_DOMAIN(c) isascii(c) +#endif + +#define ISSPACE(c) (IN_CTYPE_DOMAIN (c) && isspace (c)) +#define ISDIGIT(c) (IN_CTYPE_DOMAIN (c) && isdigit (c)) +#define TOLOWER(c) (IN_CTYPE_DOMAIN (c) ? tolower(c) : (c)) + +#include <math.h> + +#if HAVE_FLOAT_H +# include <float.h> +#else +# define DBL_MAX 1.7976931348623159e+308 +# define DBL_MIN 2.2250738585072010e-308 +#endif + +#if STDC_HEADERS +# include <stdlib.h> +# include <string.h> +#else +# define NULL 0 +# ifndef HUGE_VAL +# define HUGE_VAL HUGE +# endif +#endif + +/* Convert NPTR to a double. If ENDPTR is not NULL, a pointer to the + character after the last one used in the number is put in *ENDPTR. */ +double +strtod (const char *nptr, char **endptr) +{ + register const char *s; + short int sign; + + /* The number so far. */ + double num; + + int got_dot; /* Found a decimal point. */ + int got_digit; /* Seen any digits. */ + + /* The exponent of the number. */ + long int exponent; + + if (nptr == NULL) + { + errno = EINVAL; + goto noconv; + } + + s = nptr; + + /* Eat whitespace. */ + while (ISSPACE (*s)) + ++s; + + /* Get the sign. */ + sign = *s == '-' ? -1 : 1; + if (*s == '-' || *s == '+') + ++s; + + num = 0.0; + got_dot = 0; + got_digit = 0; + exponent = 0; + for (;; ++s) + { + if (ISDIGIT (*s)) + { + got_digit = 1; + + /* Make sure that multiplication by 10 will not overflow. */ + if (num > DBL_MAX * 0.1) + /* The value of the digit doesn't matter, since we have already + gotten as many digits as can be represented in a `double'. + This doesn't necessarily mean the result will overflow. + The exponent may reduce it to within range. + + We just need to record that there was another + digit so that we can multiply by 10 later. */ + ++exponent; + else + num = (num * 10.0) + (*s - '0'); + + /* Keep track of the number of digits after the decimal point. + If we just divided by 10 here, we would lose precision. */ + if (got_dot) + --exponent; + } + else if (!got_dot && *s == '.') + /* Record that we have found the decimal point. */ + got_dot = 1; + else + /* Any other character terminates the number. */ + break; + } + + if (!got_digit) + goto noconv; + + if (TOLOWER (*s) == 'e') + { + /* Get the exponent specified after the `e' or `E'. */ + int save = errno; + char *end; + long int exp; + + errno = 0; + ++s; + exp = strtol (s, &end, 10); + if (errno == ERANGE) + { + /* The exponent overflowed a `long int'. It is probably a safe + assumption that an exponent that cannot be represented by + a `long int' exceeds the limits of a `double'. */ + if (endptr != NULL) + *endptr = end; + if (exp < 0) + goto underflow; + else + goto overflow; + } + else if (end == s) + /* There was no exponent. Reset END to point to + the 'e' or 'E', so *ENDPTR will be set there. */ + end = (char *) s - 1; + errno = save; + s = end; + exponent += exp; + } + + if (endptr != NULL) + *endptr = (char *) s; + + if (num == 0.0) + return 0.0; + + /* Multiply NUM by 10 to the EXPONENT power, + checking for overflow and underflow. */ + + if (exponent < 0) + { + if (num < DBL_MIN * pow (10.0, (double) -exponent)) + goto underflow; + } + else if (exponent > 0) + { + if (num > DBL_MAX * pow (10.0, (double) -exponent)) + goto overflow; + } + + num *= pow (10.0, (double) exponent); + + return num * sign; + +overflow: + /* Return an overflow error. */ + errno = ERANGE; + return HUGE_VAL * sign; + +underflow: + /* Return an underflow error. */ + if (endptr != NULL) + *endptr = (char *) nptr; + errno = ERANGE; + return 0.0; + +noconv: + /* There was no number. */ + if (endptr != NULL) + *endptr = (char *) nptr; + return 0.0; +} |