1 /* Copyright (C) 1991, 1992 Free Software Foundation, Inc.
3 This program is free software; you can redistribute it and/or modify
4 it under the terms of the GNU General Public License as published by
5 the Free Software Foundation; either version 2, or (at your option)
8 This program is distributed in the hope that it will be useful,
9 but WITHOUT ANY WARRANTY; without even the implied warranty of
10 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 GNU General Public License for more details.
13 You should have received a copy of the GNU General Public License
14 along with this program; if not, write to the Free Software
15 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
28 #define DBL_MAX 1.7976931348623159e+308
29 #define DBL_MIN 2.2250738585072010e-308
43 /* Convert NPTR to a double. If ENDPTR is not NULL, a pointer to the
44 character after the last one used in the number is put in *ENDPTR. */
50 register const char *s;
53 /* The number so far. */
56 int got_dot; /* Found a decimal point. */
57 int got_digit; /* Seen any digits. */
59 /* The exponent of the number. */
75 sign = *s == '-' ? -1 : 1;
76 if (*s == '-' || *s == '+')
89 /* Make sure that multiplication by 10 will not overflow. */
90 if (num > DBL_MAX * 0.1)
91 /* The value of the digit doesn't matter, since we have already
92 gotten as many digits as can be represented in a `double'.
93 This doesn't necessarily mean the result will overflow.
94 The exponent may reduce it to within range.
96 We just need to record that there was another
97 digit so that we can multiply by 10 later. */
100 num = (num * 10.0) + (*s - '0');
102 /* Keep track of the number of digits after the decimal point.
103 If we just divided by 10 here, we would lose precision. */
107 else if (!got_dot && *s == '.')
108 /* Record that we have found the decimal point. */
111 /* Any other character terminates the number. */
118 if (tolower (*s) == 'e')
120 /* Get the exponent specified after the `e' or `E'. */
127 exp = strtol (s, &end, 10);
130 /* The exponent overflowed a `long int'. It is probably a safe
131 assumption that an exponent that cannot be represented by
132 a `long int' exceeds the limits of a `double'. */
141 /* There was no exponent. Reset END to point to
142 the 'e' or 'E', so *ENDPTR will be set there. */
143 end = (char *) s - 1;
150 *endptr = (char *) s;
155 /* Multiply NUM by 10 to the EXPONENT power,
156 checking for overflow and underflow. */
160 if (num < DBL_MIN * pow (10.0, (double) -exponent))
163 else if (exponent > 0)
165 if (num > DBL_MAX * pow (10.0, (double) -exponent))
169 num *= pow (10.0, (double) exponent);
174 /* Return an overflow error. */
176 return HUGE_VAL * sign;
179 /* Return an underflow error. */
181 *endptr = (char *) nptr;
186 /* There was no number. */
188 *endptr = (char *) nptr;