ref: b2c6c2793f7432490a3609187e8b9ecdcfc58a33
dir: /libc/fltfmt.c/
#include <u.h>
#include <libc.h>
#include <float.h>
#include <ctype.h>
#include "fmtdef.h"
enum
{
FDIGIT = 30,
FDEFLT = 6,
NSIGNIF = 17
};
/*
* first few powers of 10, enough for about 1/2 of the
* total space for doubles.
*/
static double pows10[] =
{
1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9,
1e10, 1e11, 1e12, 1e13, 1e14, 1e15, 1e16, 1e17, 1e18, 1e19,
1e20, 1e21, 1e22, 1e23, 1e24, 1e25, 1e26, 1e27, 1e28, 1e29,
1e30, 1e31, 1e32, 1e33, 1e34, 1e35, 1e36, 1e37, 1e38, 1e39,
1e40, 1e41, 1e42, 1e43, 1e44, 1e45, 1e46, 1e47, 1e48, 1e49,
1e50, 1e51, 1e52, 1e53, 1e54, 1e55, 1e56, 1e57, 1e58, 1e59,
1e60, 1e61, 1e62, 1e63, 1e64, 1e65, 1e66, 1e67, 1e68, 1e69,
1e70, 1e71, 1e72, 1e73, 1e74, 1e75, 1e76, 1e77, 1e78, 1e79,
1e80, 1e81, 1e82, 1e83, 1e84, 1e85, 1e86, 1e87, 1e88, 1e89,
1e90, 1e91, 1e92, 1e93, 1e94, 1e95, 1e96, 1e97, 1e98, 1e99,
1e100, 1e101, 1e102, 1e103, 1e104, 1e105, 1e106, 1e107, 1e108, 1e109,
1e110, 1e111, 1e112, 1e113, 1e114, 1e115, 1e116, 1e117, 1e118, 1e119,
1e120, 1e121, 1e122, 1e123, 1e124, 1e125, 1e126, 1e127, 1e128, 1e129,
1e130, 1e131, 1e132, 1e133, 1e134, 1e135, 1e136, 1e137, 1e138, 1e139,
1e140, 1e141, 1e142, 1e143, 1e144, 1e145, 1e146, 1e147, 1e148, 1e149,
1e150, 1e151, 1e152, 1e153, 1e154, 1e155, 1e156, 1e157, 1e158, 1e159,
};
#undef pow10
#define pow10(x) fmtpow10(x)
static double
pow10(int n)
{
double d;
int neg;
neg = 0;
if(n < 0){
if(n < DBL_MIN_10_EXP){
return 0.;
}
neg = 1;
n = -n;
}else if(n > DBL_MAX_10_EXP){
return HUGE_VAL;
}
if(n < (int)(sizeof(pows10)/sizeof(pows10[0])))
d = pows10[n];
else{
d = pows10[sizeof(pows10)/sizeof(pows10[0]) - 1];
for(;;){
n -= sizeof(pows10)/sizeof(pows10[0]) - 1;
if(n < (int)(sizeof(pows10)/sizeof(pows10[0]))){
d *= pows10[n];
break;
}
d *= pows10[sizeof(pows10)/sizeof(pows10[0]) - 1];
}
}
if(neg){
return 1./d;
}
return d;
}
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;
}
static int
floatfmt(Fmt *fmt, double f)
{
char s[341]; /* precision+exponent+sign+'.'+null */
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);
}