shithub: riscv

ref: a021f054b0aaba768b9182dadd2da4b76fdf9576
dir: /sys/src/cmd/python/Python/atof.c/

/* Just in case you haven't got an atof() around...
   This one doesn't check for bad syntax or overflow,
   and is slow and inaccurate.
   But it's good enough for the occasional string literal... */

#include "pyconfig.h"

#include <ctype.h>

double atof(char *s)
{
	double a = 0.0;
	int e = 0;
	int c;
	while ((c = *s++) != '\0' && isdigit(c)) {
		a = a*10.0 + (c - '0');
	}
	if (c == '.') {
		while ((c = *s++) != '\0' && isdigit(c)) {
			a = a*10.0 + (c - '0');
			e = e-1;
		}
	}
	if (c == 'e' || c == 'E') {
		int sign = 1;
		int i = 0;
		c = *s++;
		if (c == '+')
			c = *s++;
		else if (c == '-') {
			c = *s++;
			sign = -1;
		}
		while (isdigit(c)) {
			i = i*10 + (c - '0');
			c = *s++;
		}
		e += i*sign;
	}
	while (e > 0) {
		a *= 10.0;
		e--;
	}
	while (e < 0) {
		a *= 0.1;
		e++;
	}
	return a;
}