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2 - 1 
#include <u.h>
2 
#include <libc.h>
3 
#include <ctype.h>
4 
#include "fmtdef.h"
5 
 
6 
enum
7 
{
8 
	FDIGIT	= 30,
9 
	FDEFLT	= 6,
10 
	NSIGNIF	= 17,
11 
	NEXP10	= 308,
12 
};
13 
 
14 
static int
15 
xadd(char *a, int n, int v)
16 
{
17 
	char *b;
18 
	int c;
19 
 
20 
	if(n < 0 || n >= NSIGNIF)
21 
		return 0;
22 
	for(b = a+n; b >= a; b--) {
23 
		c = *b + v;
24 
		if(c <= '9') {
25 
			*b = c;
26 
			return 0;
27 
		}
28 
		*b = '0';
29 
		v = 1;
30 
	}
31 
	*a = '1';	// overflow adding
32 
	return 1;
33 
}
34 
 
35 
static int
36 
xsub(char *a, int n, int v)
37 
{
38 
	char *b;
39 
	int c;
40 
 
41 
	for(b = a+n; b >= a; b--) {
42 
		c = *b - v;
43 
		if(c >= '0') {
44 
			*b = c;
45 
			return 0;
46 
		}
47 
		*b = '9';
48 
		v = 1;
49 
	}
50 
	*a = '9';	// underflow subtracting
51 
	return 1;
52 
}
53 
 
54 
static void
55 
xdtoa(Fmt *fmt, char *s2, double f)
56 
{
57 
	char s1[NSIGNIF+10];
58 
	double g, h;
59 
	int e, d, i, n;
60 
	int c1, c2, c3, c4, ucase, sign, chr, prec;
61 
 
62 
	prec = FDEFLT;
63 
	if(fmt->flags & FmtPrec)
64 
		prec = fmt->prec;
65 
	if(prec > FDIGIT)
66 
		prec = FDIGIT;
67 
	if(isNaN(f)) {
68 
		strcpy(s2, "NaN");
69 
		return;
70 
	}
71 
	if(isInf(f, 1)) {
72 
		strcpy(s2, "+Inf");
73 
		return;
74 
	}
75 
	if(isInf(f, -1)) {
76 
		strcpy(s2, "-Inf");
77 
		return;
78 
	}
79 
	sign = 0;
80 
	if(f < 0) {
81 
		f = -f;
82 
		sign++;
83 
	}
84 
	ucase = 0;
85 
	chr = fmt->r;
86 
	if(isupper(chr)) {
87 
		ucase = 1;
88 
		chr = tolower(chr);
89 
	}
90 
 
91 
	e = 0;
92 
	g = f;
93 
	if(g != 0) {
94 
		frexp(f, &e);
95 
		e = e * .301029995664;
96 
		if(e >= -150 && e <= +150) {
97 
			d = 0;
98 
			h = f;
99 
		} else {
100 
			d = e/2;
101 
			h = f * pow10(-d);
102 
		}
103 
		g = h * pow10(d-e);
104 
		while(g < 1) {
105 
			e--;
106 
			g = h * pow10(d-e);
107 
		}
108 
		while(g >= 10) {
109 
			e++;
110 
			g = h * pow10(d-e);
111 
		}
112 
	}
113 
 
114 
	/*
115 
	 * convert NSIGNIF digits and convert
116 
	 * back to get accuracy.
117 
	 */
118 
	for(i=0; i<NSIGNIF; i++) {
119 
		d = g;
120 
		s1[i] = d + '0';
121 
		g = (g - d) * 10;
122 
	}
123 
	s1[i] = 0;
124 
 
125 
	/*
126 
	 * try decimal rounding to eliminate 9s
127 
	 */
128 
	c2 = prec + 1;
129 
	if(chr == 'f')
130 
		c2 += e;
131 
	if(c2 >= NSIGNIF-2) {
132 
		strcpy(s2, s1);
133 
		d = e;
134 
		s1[NSIGNIF-2] = '0';
135 
		s1[NSIGNIF-1] = '0';
136 
		sprint(s1+NSIGNIF, "e%d", e-NSIGNIF+1);
137 
		g = strtod(s1, nil);
138 
		if(g == f)
139 
			goto found;
140 
		if(xadd(s1, NSIGNIF-3, 1)) {
141 
			e++;
142 
			sprint(s1+NSIGNIF, "e%d", e-NSIGNIF+1);
143 
		}
144 
		g = strtod(s1, nil);
145 
		if(g == f)
146 
			goto found;
147 
		strcpy(s1, s2);
148 
		e = d;
149 
	}
150 
 
151 
	/*
152 
	 * convert back so s1 gets exact answer
153 
	 */
154 
	for(;;) {
155 
		sprint(s1+NSIGNIF, "e%d", e-NSIGNIF+1);
156 
		g = strtod(s1, nil);
157 
		if(f > g) {
158 
			if(xadd(s1, NSIGNIF-1, 1))
159 
				e--;
160 
			continue;
161 
		}
162 
		if(f < g) {
163 
			if(xsub(s1, NSIGNIF-1, 1))
164 
				e++;
165 
			continue;
166 
		}
167 
		break;
168 
	}
169 
 
170 
found:
171 
	/*
172 
	 * sign
173 
	 */
174 
	d = 0;
175 
	i = 0;
176 
	if(sign)
177 
		s2[d++] = '-';
178 
	else if(fmt->flags & FmtSign)
179 
		s2[d++] = '+';
180 
	else if(fmt->flags & FmtSpace)
181 
		s2[d++] = ' ';
182 
 
183 
	/*
184 
	 * copy into final place
185 
	 * c1 digits of leading '0'
186 
	 * c2 digits from conversion
187 
	 * c3 digits of trailing '0'
188 
	 * c4 digits after '.'
189 
	 */
190 
	c1 = 0;
191 
	c2 = prec + 1;
192 
	c3 = 0;
193 
	c4 = prec;
194 
	switch(chr) {
195 
	default:
196 
		if(xadd(s1, c2, 5))
197 
			e++;
198 
		break;
199 
	case 'g':
200 
		/*
201 
		 * decide on 'e' of 'f' style convers
202 
		 */
203 
		if(xadd(s1, c2, 5))
204 
			e++;
205 
		if(e >= -5 && e <= prec) {
206 
			c1 = -e - 1;
207 
			c4 = prec - e;
208 
			chr = 'h';	// flag for 'f' style
209 
		}
210 
		break;
211 
	case 'f':
212 
		if(xadd(s1, c2+e, 5))
213 
			e++;
214 
		c1 = -e;
215 
		if(c1 > prec)
216 
			c1 = c2;
217 
		c2 += e;
218 
		break;
219 
	}
220 
 
221 
	/*
222 
	 * clean up c1 c2 and c3
223 
	 */
224 
	if(c1 < 0)
225 
		c1 = 0;
226 
	if(c2 < 0)
227 
		c2 = 0;
228 
	if(c2 > NSIGNIF) {
229 
		c3 = c2-NSIGNIF;
230 
		c2 = NSIGNIF;
231 
	}
232 
 
233 
	/*
234 
	 * copy digits
235 
	 */
236 
	while(c1 > 0) {
237 
		if(c1+c2+c3 == c4)
238 
			s2[d++] = '.';
239 
		s2[d++] = '0';
240 
		c1--;
241 
	}
242 
	while(c2 > 0) {
243 
		if(c2+c3 == c4)
244 
			s2[d++] = '.';
245 
		s2[d++] = s1[i++];
246 
		c2--;
247 
	}
248 
	while(c3 > 0) {
249 
		if(c3 == c4)
250 
			s2[d++] = '.';
251 
		s2[d++] = '0';
252 
		c3--;
253 
	}
254 
 
255 
	/*
256 
	 * strip trailing '0' on g conv
257 
	 */
258 
	if(fmt->flags & FmtSharp) {
259 
		if(0 == c4)
260 
			s2[d++] = '.';
261 
	} else
262 
	if(chr == 'g' || chr == 'h') {
263 
		for(n=d-1; n>=0; n--)
264 
			if(s2[n] != '0')
265 
				break;
266 
		for(i=n; i>=0; i--)
267 
			if(s2[i] == '.') {
268 
				d = n;
269 
				if(i != n)
270 
					d++;
271 
				break;
272 
			}
273 
	}
274 
	if(chr == 'e' || chr == 'g') {
275 
		if(ucase)
276 
			s2[d++] = 'E';
277 
		else
278 
			s2[d++] = 'e';
279 
		c1 = e;
280 
		if(c1 < 0) {
281 
			s2[d++] = '-';
282 
			c1 = -c1;
283 
		} else
284 
			s2[d++] = '+';
285 
		if(c1 >= 100) {
286 
			s2[d++] = c1/100 + '0';
287 
			c1 = c1%100;
288 
		}
289 
		s2[d++] = c1/10 + '0';
290 
		s2[d++] = c1%10 + '0';
291 
	}
292 
	s2[d] = 0;
293 
}
294 
 
295 
int
296 
_floatfmt(Fmt *fmt, double f)
297 
{
298 
	char s[1+NEXP10+1+FDIGIT+1];
299 
 
300 
	/*
301 
	 * The max length of a %f string is
302 
	 *	'[+-]'+"max exponent"+'.'+"max precision"+'\0'
303 
	 * which is 341 currently.
304 
	 */
305 
	xdtoa(fmt, s, f);
306 
	fmt->flags &= FmtWidth|FmtLeft;
307 
	_fmtcpy(fmt, s, strlen(s), strlen(s));
308 
	return 0;
309 
}
310 
 
311 
int
312 
_efgfmt(Fmt *f)
313 
{
314 
	double d;
315 
 
316 
	d = va_arg(f->args, double);
317 
	return _floatfmt(f, d);
318 
}