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