2 * The authors of this software are Rob Pike and Ken Thompson.
3 * Copyright (c) 2002 by Lucent Technologies.
4 * Permission to use, copy, modify, and distribute this software for any
5 * purpose without fee is hereby granted, provided that this entire notice
6 * is included in all copies of any software which is or includes a copy
7 * or modification of this software and in all copies of the supporting
8 * documentation for such software.
9 * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
10 * WARRANTY. IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES MAKE
11 * ANY REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY
12 * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
35 * first few powers of 10, enough for about 1/2 of the
36 * total space for doubles.
38 static double pows10[] =
40 1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9,
41 1e10, 1e11, 1e12, 1e13, 1e14, 1e15, 1e16, 1e17, 1e18, 1e19,
42 1e20, 1e21, 1e22, 1e23, 1e24, 1e25, 1e26, 1e27, 1e28, 1e29,
43 1e30, 1e31, 1e32, 1e33, 1e34, 1e35, 1e36, 1e37, 1e38, 1e39,
44 1e40, 1e41, 1e42, 1e43, 1e44, 1e45, 1e46, 1e47, 1e48, 1e49,
45 1e50, 1e51, 1e52, 1e53, 1e54, 1e55, 1e56, 1e57, 1e58, 1e59,
46 1e60, 1e61, 1e62, 1e63, 1e64, 1e65, 1e66, 1e67, 1e68, 1e69,
47 1e70, 1e71, 1e72, 1e73, 1e74, 1e75, 1e76, 1e77, 1e78, 1e79,
48 1e80, 1e81, 1e82, 1e83, 1e84, 1e85, 1e86, 1e87, 1e88, 1e89,
49 1e90, 1e91, 1e92, 1e93, 1e94, 1e95, 1e96, 1e97, 1e98, 1e99,
50 1e100, 1e101, 1e102, 1e103, 1e104, 1e105, 1e106, 1e107, 1e108, 1e109,
51 1e110, 1e111, 1e112, 1e113, 1e114, 1e115, 1e116, 1e117, 1e118, 1e119,
52 1e120, 1e121, 1e122, 1e123, 1e124, 1e125, 1e126, 1e127, 1e128, 1e129,
53 1e130, 1e131, 1e132, 1e133, 1e134, 1e135, 1e136, 1e137, 1e138, 1e139,
54 1e140, 1e141, 1e142, 1e143, 1e144, 1e145, 1e146, 1e147, 1e148, 1e149,
55 1e150, 1e151, 1e152, 1e153, 1e154, 1e155, 1e156, 1e157, 1e158, 1e159,
58 #define pow10(x) fmtpow10(x)
68 if(n < DBL_MIN_10_EXP){
73 }else if(n > DBL_MAX_10_EXP){
76 if(n < (int)(sizeof(pows10)/sizeof(pows10[0])))
79 d = pows10[sizeof(pows10)/sizeof(pows10[0]) - 1];
81 n -= sizeof(pows10)/sizeof(pows10[0]) - 1;
82 if(n < (int)(sizeof(pows10)/sizeof(pows10[0]))){
86 d *= pows10[sizeof(pows10)/sizeof(pows10[0]) - 1];
96 xadd(char *a, int n, int v)
101 if(n < 0 || n >= NSIGNIF)
103 for(b = a+n; b >= a; b--) {
112 *a = '1'; /* overflow adding */
117 xsub(char *a, int n, int v)
122 for(b = a+n; b >= a; b--) {
131 *a = '9'; /* underflow subtracting */
136 xdtoa(Fmt *fmt, char *s2, double f)
141 int c1, c2, c3, c4, ucase, sign, chr, prec;
144 if(fmt->flags & FmtPrec)
176 e = e * .301029995664;
177 if(e >= -150 && e <= +150) {
196 * convert NSIGNIF digits and convert
197 * back to get accuracy.
199 for(i=0; i<NSIGNIF; i++) {
207 * try decimal rounding to eliminate 9s
212 if(c2 >= NSIGNIF-2) {
217 sprint(s1+NSIGNIF, "e%d", e-NSIGNIF+1);
221 if(xadd(s1, NSIGNIF-3, 1)) {
223 sprint(s1+NSIGNIF, "e%d", e-NSIGNIF+1);
233 * convert back so s1 gets exact answer
236 sprint(s1+NSIGNIF, "e%d", e-NSIGNIF+1);
239 if(xadd(s1, NSIGNIF-1, 1))
244 if(xsub(s1, NSIGNIF-1, 1))
259 else if(fmt->flags & FmtSign)
261 else if(fmt->flags & FmtSpace)
265 * copy into final place
266 * c1 digits of leading '0'
267 * c2 digits from conversion
268 * c3 digits of trailing '0'
269 * c4 digits after '.'
282 * decide on 'e' of 'f' style convers
286 if(e >= -5 && e <= prec) {
289 chr = 'h'; // flag for 'f' style
293 if(xadd(s1, c2+e, 5))
303 * clean up c1 c2 and c3
337 * strip trailing '0' on g conv
339 if(fmt->flags & FmtSharp) {
343 if(chr == 'g' || chr == 'h') {
344 for(n=d-1; n>=0; n--)
355 if(chr == 'e' || chr == 'g') {
367 s2[d++] = c1/100 + '0';
370 s2[d++] = c1/10 + '0';
371 s2[d++] = c1%10 + '0';
377 floatfmt(Fmt *fmt, double f)
379 char s[341]; /* precision+exponent+sign+'.'+null */
382 fmt->flags &= FmtWidth|FmtLeft;
383 __fmtcpy(fmt, s, strlen(s), strlen(s));
392 d = va_arg(f->args, double);
393 return floatfmt(f, d);