int
Fconv(Fmt *fp)
{
char buf[500];
Mpflt *fvp, fv;
double d;
fvp = va_arg(fp->args, Mpflt*);
if(fp->flags & FmtSharp) {
// alternate form - decimal for error messages.
// for well in range, convert to double and use print's %g
if(-900 < fvp->exp && fvp->exp < 900) {
d = mpgetflt(fvp);
if(d >= 0 && (fp->flags & FmtSign))
fmtprint(fp, "+");
return fmtprint(fp, "%g", d);
}
// TODO(rsc): for well out of range, print
// an approximation like 1.234e1000
}
if(sigfig(fvp) == 0) {
snprint(buf, sizeof(buf), "0p+0");
goto out;
}
fv = *fvp;
while(fv.val.a[0] == 0) {
mpshiftfix(&fv.val, -Mpscale);
fv.exp += Mpscale;
}
while((fv.val.a[0]&1) == 0) {
mpshiftfix(&fv.val, -1);
fv.exp += 1;
}
if(fv.exp >= 0) {
snprint(buf, sizeof(buf), "%#Bp+%d", &fv.val, fv.exp);
goto out;
}
snprint(buf, sizeof(buf), "%#Bp-%d", &fv.val, -fv.exp);
out:
return fmtstrcpy(fp, buf);
}
// convert (truncate) b to a.
// return -1 (but still convert) if b was non-integer.
int
mpmovefltfix(Mpint *a, Mpflt *b)
{
Mpflt f;
*a = b->val;
mpshiftfix(a, b->exp);
if(b->exp < 0) {
f.val = *a;
f.exp = 0;
mpnorm(&f);
if(mpcmpfltflt(b, &f) != 0)
return -1;
}
return 0;
}
void
mplshfixfix(Mpint *a, Mpint *b)
{
vlong s;
if(a->ovf || b->ovf) {
yyerror("ovf in mporfixfix");
mpmovecfix(a, 0);
a->ovf = 1;
return;
}
s = mpgetfix(b);
if(s < 0 || s >= Mpprec*Mpscale) {
yyerror("stupid shift: %lld", s);
mpmovecfix(a, 0);
return;
}
mpshiftfix(a, s);
}
int
Fconv(Fmt *fp)
{
char buf[500];
Mpflt *fvp, fv;
double d, dexp;
int exp;
fvp = va_arg(fp->args, Mpflt*);
if(fp->flags & FmtSharp) {
// alternate form - decimal for error messages.
// for well in range, convert to double and use print's %g
exp = fvp->exp + sigfig(fvp)*Mpscale;
if(-900 < exp && exp < 900) {
d = mpgetflt(fvp);
if(d >= 0 && (fp->flags & FmtSign))
fmtprint(fp, "+");
return fmtprint(fp, "%g", d, exp, fvp);
}
// very out of range. compute decimal approximation by hand.
// decimal exponent
dexp = fvp->exp * 0.301029995663981195; // log_10(2)
exp = (int)dexp;
// decimal mantissa
fv = *fvp;
fv.val.neg = 0;
fv.exp = 0;
d = mpgetflt(&fv);
d *= pow(10, dexp-exp);
while(d >= 9.99995) {
d /= 10;
exp++;
}
if(fvp->val.neg)
fmtprint(fp, "-");
else if(fp->flags & FmtSign)
fmtprint(fp, "+");
return fmtprint(fp, "%.5fe+%d", d, exp);
}
if(sigfig(fvp) == 0) {
snprint(buf, sizeof(buf), "0p+0");
goto out;
}
fv = *fvp;
while(fv.val.a[0] == 0) {
mpshiftfix(&fv.val, -Mpscale);
fv.exp += Mpscale;
}
while((fv.val.a[0]&1) == 0) {
mpshiftfix(&fv.val, -1);
fv.exp += 1;
}
if(fv.exp >= 0) {
snprint(buf, sizeof(buf), "%#Bp+%d", &fv.val, fv.exp);
goto out;
}
snprint(buf, sizeof(buf), "%#Bp-%d", &fv.val, -fv.exp);
out:
return fmtstrcpy(fp, buf);
}
