a

libc/fltfmt.c

@@ -0,0 +1,312 @@
+#include <u.h>
+#include <libc.h>
+#include <ctype.h>
+#include "fmtdef.h"
+
+enum
+{
+	FDIGIT	= 30,
+	FDEFLT	= 6,
+	NSIGNIF	= 17,
+};
+
+static int
+xadd(char *a, int n, int v)
+{
+	char *b;
+	int c;
+
+	if(n < 0 || n >= NSIGNIF)
+		return 0;
+	for(b = a+n; b >= a; b--) {
+		c = *b + v;
+		if(c <= '9') {
+			*b = c;
+			return 0;
+		}
+		*b = '0';
+		v = 1;
+	}
+	*a = '1';	// overflow adding
+	return 1;
+}
+
+static int
+xsub(char *a, int n, int v)
+{
+	char *b;
+	int c;
+
+	for(b = a+n; b >= a; b--) {
+		c = *b - v;
+		if(c >= '0') {
+			*b = c;
+			return 0;
+		}
+		*b = '9';
+		v = 1;
+	}
+	*a = '9';	// underflow subtracting
+	return 1;
+}
+
+static void
+xdtoa(Fmt *fmt, char *s2, double f)
+{
+	char s1[NSIGNIF+10];
+	double g, h;
+	int e, d, i, n;
+	int c1, c2, c3, c4, ucase, sign, chr, prec;
+
+	prec = FDEFLT;
+	if(fmt->flags & FmtPrec)
+		prec = fmt->prec;
+	if(prec > FDIGIT)
+		prec = FDIGIT;
+	if(__isNaN(f)) {
+		strcpy(s2, "NaN");
+		return;
+	}
+	if(__isInf(f, 1)) {
+		strcpy(s2, "+Inf");
+		return;
+	}
+	if(__isInf(f, -1)) {
+		strcpy(s2, "-Inf");
+		return;
+	}
+	sign = 0;
+	if(f < 0) {
+		f = -f;
+		sign++;
+	}
+	ucase = 0;
+	chr = fmt->r;
+	if(isupper(chr)) {
+		ucase = 1;
+		chr = tolower(chr);
+	}
+
+	e = 0;
+	g = f;
+	if(g != 0) {
+		frexp(f, &e);
+		e = e * .301029995664;
+		if(e >= -150 && e <= +150) {
+			d = 0;
+			h = f;
+		} else {
+			d = e/2;
+			h = f * pow10(-d);
+		}
+		g = h * pow10(d-e);
+		while(g < 1) {
+			e--;
+			g = h * pow10(d-e);
+		}
+		while(g >= 10) {
+			e++;
+			g = h * pow10(d-e);
+		}
+	}
+
+	/*
+	 * convert NSIGNIF digits and convert
+	 * back to get accuracy.
+	 */
+	for(i=0; i<NSIGNIF; i++) {
+		d = g;
+		s1[i] = d + '0';
+		g = (g - d) * 10;
+	}
+	s1[i] = 0;
+
+	/*
+	 * try decimal rounding to eliminate 9s
+	 */
+	c2 = prec + 1;
+	if(chr == 'f')
+		c2 += e;
+	if(c2 >= NSIGNIF-2) {
+		strcpy(s2, s1);
+		d = e;
+		s1[NSIGNIF-2] = '0';
+		s1[NSIGNIF-1] = '0';
+		sprint(s1+NSIGNIF, "e%d", e-NSIGNIF+1);
+		g = strtod(s1, nil);
+		if(g == f)
+			goto found;
+		if(xadd(s1, NSIGNIF-3, 1)) {
+			e++;
+			sprint(s1+NSIGNIF, "e%d", e-NSIGNIF+1);
+		}
+		g = strtod(s1, nil);
+		if(g == f)
+			goto found;
+		strcpy(s1, s2);
+		e = d;
+	}
+
+	/*
+	 * convert back so s1 gets exact answer
+	 */
+	for(;;) {
+		sprint(s1+NSIGNIF, "e%d", e-NSIGNIF+1);
+		g = strtod(s1, nil);
+		if(f > g) {
+			if(xadd(s1, NSIGNIF-1, 1))
+				e--;
+			continue;
+		}
+		if(f < g) {
+			if(xsub(s1, NSIGNIF-1, 1))
+				e++;
+			continue;
+		}
+		break;
+	}
+
+found:
+	/*
+	 * sign
+	 */
+	d = 0;
+	i = 0;
+	if(sign)
+		s2[d++] = '-';
+	else if(fmt->flags & FmtSign)
+		s2[d++] = '+';
+	else if(fmt->flags & FmtSpace)
+		s2[d++] = ' ';
+
+	/*
+	 * copy into final place
+	 * c1 digits of leading '0'
+	 * c2 digits from conversion
+	 * c3 digits of trailing '0'
+	 * c4 digits after '.'
+	 */
+	c1 = 0;
+	c2 = prec + 1;
+	c3 = 0;
+	c4 = prec;
+	switch(chr) {
+	default:
+		if(xadd(s1, c2, 5))
+			e++;
+		break;
+	case 'g':
+		/*
+		 * decide on 'e' of 'f' style convers
+		 */
+		if(xadd(s1, c2, 5))
+			e++;
+		if(e >= -5 && e <= prec) {
+			c1 = -e - 1;
+			c4 = prec - e;
+			chr = 'h';	// flag for 'f' style
+		}
+		break;
+	case 'f':
+		if(xadd(s1, c2+e, 5))
+			e++;
+		c1 = -e;
+		if(c1 > prec)
+			c1 = c2;
+		c2 += e;
+		break;
+	}
+
+	/*
+	 * clean up c1 c2 and c3
+	 */
+	if(c1 < 0)
+		c1 = 0;
+	if(c2 < 0)
+		c2 = 0;
+	if(c2 > NSIGNIF) {
+		c3 = c2-NSIGNIF;
+		c2 = NSIGNIF;
+	}
+
+	/*
+	 * copy digits
+	 */
+	while(c1 > 0) {
+		if(c1+c2+c3 == c4)
+			s2[d++] = '.';
+		s2[d++] = '0';
+		c1--;
+	}
+	while(c2 > 0) {
+		if(c2+c3 == c4)
+			s2[d++] = '.';
+		s2[d++] = s1[i++];
+		c2--;
+	}
+	while(c3 > 0) {
+		if(c3 == c4)
+			s2[d++] = '.';
+		s2[d++] = '0';
+		c3--;
+	}
+
+	/*
+	 * strip trailing '0' on g conv
+	 */
+	if(fmt->flags & FmtSharp) {
+		if(0 == c4)
+			s2[d++] = '.';
+	} else
+	if(chr == 'g' || chr == 'h') {
+		for(n=d-1; n>=0; n--)
+			if(s2[n] != '0')
+				break;
+		for(i=n; i>=0; i--)
+			if(s2[i] == '.') {
+				d = n;
+				if(i != n)
+					d++;
+				break;
+			}
+	}
+	if(chr == 'e' || chr == 'g') {
+		if(ucase)
+			s2[d++] = 'E';
+		else
+			s2[d++] = 'e';
+		c1 = e;
+		if(c1 < 0) {
+			s2[d++] = '-';
+			c1 = -c1;
+		} else
+			s2[d++] = '+';
+		if(c1 >= 100) {
+			s2[d++] = c1/100 + '0';
+			c1 = c1%100;
+		}
+		s2[d++] = c1/10 + '0';
+		s2[d++] = c1%10 + '0';
+	}
+	s2[d] = 0;
+}
+
+int
+_floatfmt(Fmt *fmt, double f)
+{
+	char s[FDIGIT+10];
+
+	xdtoa(fmt, s, f);
+	fmt->flags &= FmtWidth|FmtLeft;
+	_fmtcpy(fmt, s, strlen(s), strlen(s));
+	return 0;
+}
+
+int
+_efgfmt(Fmt *f)
+{
+	double d;
+
+	d = va_arg(f->args, double);
+	return _floatfmt(f, d);
+}