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/*
* strtod.c
*
* Stupid version of System V strtod(3) library routine.
* Does no overflow/underflow checking.
*
* A real number is defined to be
* optional leading white space
* optional sign
* string of digits with optional decimal point
* optional 'e' or 'E'
* followed by optional sign or space
* followed by an integer
*
* if ptr is not NULL a pointer to the character terminating the
* scan is returned in *ptr. If no number formed, *ptr is set to str
* and 0 is returned.
*
* For speed, we don't do the conversion ourselves. Instead, we find
* the end of the number and then call atof() to do the dirty work.
* This bought us a 10% speedup on a sample program at uunet.uu.net.
*/
#if 0
#include <ctype.h>
#endif
extern double atof();
double
strtod (s, ptr)
register const char *s;
register char **ptr;
{
double ret = 0.0;
char *start = s;
char *begin = NULL;
int success = 0;
/* optional white space */
while (isspace(*s))
s++;
/* optional sign */
if (*s == '+' || *s == '-') {
s++;
if (*(s-1) == '-')
begin = s - 1;
else
begin = s;
}
/* string of digits with optional decimal point */
if (isdigit(*s) && ! begin)
begin = s;
while (isdigit(*s)) {
s++;
success++;
}
if (*s == '.') {
if (! begin)
begin = s;
s++;
while (isdigit(*s))
s++;
success++;
}
if (s == start || success == 0) /* nothing there */
goto out;
/*
* optional 'e' or 'E'
* followed by optional sign or space
* followed by an integer
*/
if (*s == 'e' || *s == 'E') {
s++;
/* XXX - atof probably doesn't allow spaces here */
while (isspace(*s))
s++;
if (*s == '+' || *s == '-')
s++;
while (isdigit(*s))
s++;
}
/* go for it */
ret = atof(begin);
out:
if (! success)
s = start; /* in case all we did was skip whitespace */
if (ptr)
*ptr = s;
return ret;
}
#ifdef TEST
main (argc, argv)
int argc;
char **argv;
{
double d;
char *p;
for (argc--, argv++; argc; argc--, argv++) {
d = strtod (*argv, & p);
printf ("%lf [%s]\n", d, p);
}
}
#endif
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