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- #include <u.h>
- #include <libc.h>
- #include <ctype.h>
- #include "fmtdef.h"
- enum
- {
- FDIGIT = 30,
- FDEFLT = 6,
- NSIGNIF = 17,
- NEXP10 = 308,
- };
- 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[1+NEXP10+1+FDIGIT+1];
- /*
- * The max length of a %f string is
- * '[+-]'+"max exponent"+'.'+"max precision"+'\0'
- * which is 341 currently.
- */
- 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);
- }
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