[9fans] charstod

[9fans] charstod

[erik quanstrom]

i have a proposal for charstod that should allow it
to recognize numbers without trailing non number
characters.

	int	xcharstod(int(*f)(void*), void *vp, double *g)

returning -1 on failure to parse a number, and 0
otherwise.  in addition, g is set to 0. on failure, not
NaN in keeping with strtod.

the two uses in /sys/src are:

sys/src//cmd/units.y:272: 	yylval.val = charstod(gdigit, 0);
/sys/src//libbio/bgetd.c:31: 	d = charstod(Bgetdf, &b);

it would seem easy enough to update them to match.
eof tracking in Bgetd could just be dleted.

also, this orphan function should likely be retired:

/sys/src/ape/lib/fmt/charstod.c:28: fmtcharstod(int(*f)(void*), void *vp)
/sys/src/cmd/unix/drawterm/libc/charstod.c:13: fmtcharstod(int(*f)(void*), void *vp)
/sys/include/ape/fmt.h:106: extern	double	fmtcharstod(int(*)(void*), void*);

- erik

-----

#include <u.h>
#include <libc.h>

/*
 * Reads a floating-point number by interpreting successive characters
 * returned by (*f)(vp).  The last call it makes to f terminates the
 * scan, so is not a character in the number.  It may therefore be
 * necessary to back up the input stream up one byte after calling charstod.
 */

#define ADVANCE *s++ = c; if(s>=e) return -1; c = (*f)(vp)

int
xcharstod(int(*f)(void*), void *vp, double *g)
{
	char str[400], *s, *e, *start;
	int c;

	*g = 0.;
	s = str;
	e = str + sizeof str - 1;
	c = (*f)(vp);
	while(c == ' ' || c == '\t')
		c = (*f)(vp);
	if(c == '-' || c == '+'){
		ADVANCE;
	}
	start = s;
	while(c >= '0' && c <= '9'){
		ADVANCE;
	}
	if(c == '.'){
		ADVANCE;
		while(c >= '0' && c <= '9'){
			ADVANCE;
		}
	}
	if(s > start && (c == 'e' || c == 'E')){
		ADVANCE;
		if(c == '-' || c == '+'){
			ADVANCE;
		}
		while(c >= '0' && c <= '9'){
			ADVANCE;
		}
	}else if(s == start && (c == 'i' || c == 'I')){
		ADVANCE;
		if(c != 'n' && c != 'N')
			return -1;
		ADVANCE;
		if(c != 'f' && c != 'F')
			return -1;
		ADVANCE;
		if(c != 'i' && c != 'I')
			goto accept;
		ADVANCE;
		if(c != 'n' && c != 'N')
			return -1;
		ADVANCE;
		if(c != 'i' && c != 'I')
			return -1;
		ADVANCE;
		if(c != 't' && c != 'T')
			return -1;
		ADVANCE;
		if(c != 'y' && c != 'Y')
			return -1;
		ADVANCE;  /* so caller can back up uniformly */
		USED(c);
	}else if(s == str && (c == 'n' || c == 'N')){
		ADVANCE;
		if(c != 'a' && c != 'A')
			return -1;
		ADVANCE;
		if(c != 'n' && c != 'N')
			return -1;
		ADVANCE;  /* so caller can back up uniformly */
		USED(c);
	}
accept:
	*s = 0;
	*g = strtod(str, &s);
	if(s > str)
		return 0;
	return -1;
}