cosmopolitan/third_party/gdtoa/dtoa.c
Justine Tunney fa20edc44d
Reduce header complexity
- Remove most __ASSEMBLER__ __LINKER__ ifdefs
- Rename libc/intrin/bits.h to libc/serialize.h
- Block pthread cancelation in fchmodat() polyfill
- Remove `clang-format off` statements in third_party
2023-11-28 14:39:42 -08:00

622 lines
17 KiB
C

/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8 -*-│
│vi: set et ft=c ts=8 tw=8 fenc=utf-8 :vi│
╚──────────────────────────────────────────────────────────────────────────────╝
│ │
│ The author of this software is David M. Gay. │
│ Please send bug reports to David M. Gay <dmg@acm.org> │
│ or Justine Tunney <jtunney@gmail.com> │
│ │
│ Copyright (C) 1998, 1999 by Lucent Technologies │
│ All Rights Reserved │
│ │
│ Permission to use, copy, modify, and distribute this software and │
│ its documentation for any purpose and without fee is hereby │
│ granted, provided that the above copyright notice appear in all │
│ copies and that both that the copyright notice and this │
│ permission notice and warranty disclaimer appear in supporting │
│ documentation, and that the name of Lucent or any of its entities │
│ not be used in advertising or publicity pertaining to │
│ distribution of the software without specific, written prior │
│ permission. │
│ │
│ LUCENT DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, │
│ INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. │
│ IN NO EVENT SHALL LUCENT OR ANY OF ITS ENTITIES BE LIABLE FOR ANY │
│ SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES │
│ WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER │
│ IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, │
│ ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF │
│ THIS SOFTWARE. │
│ │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/runtime/fenv.h"
#include "third_party/gdtoa/gdtoa.internal.h"
/* dtoa for IEEE arithmetic (dmg): convert double to ASCII string.
*
* Inspired by "How to Print Floating-Point Numbers Accurately" by
* Guy L. Steele, Jr. and Jon L. White [Proc. ACM SIGPLAN '90, pp. 112-126].
*
* Modifications:
* 1. Rather than iterating, we use a simple numeric overestimate
* to determine k = floor(log10(d)). We scale relevant
* quantities using O(log2(k)) rather than O(k) __gdtoa_multiplications.
* 2. For some modes > 2 (corresponding to ecvt and fcvt), we don't
* try to generate digits strictly left to right. Instead, we
* compute with fewer bits and propagate the carry if necessary
* when rounding the final digit up. This is often faster.
* 3. Under the as__gdtoa_sumption that input will be rounded nearest,
* mode 0 renders 1e23 as 1e23 rather than 9.999999999999999e22.
* That is, we allow equality in stopping tests when the
* round-nearest rule will give the same floating-point value
* as would satisfaction of the stopping test with strict
* inequality.
* 4. We remove common factors of powers of 2 from relevant
* quantities.
* 5. When converting floating-point integers less than 1e16,
* we use floating-point arithmetic rather than resorting
* to __gdtoa_multiple-precision integers.
* 6. When asked to produce fewer than 15 digits, we first try
* to get by with floating-point arithmetic; we resort to
* __gdtoa_multiple-precision integer arithmetic only if we cannot
* guarantee that the floating-point calculation has given
* the correctly rounded result. For k requested digits and
* "uniformly" distributed input, the probability is
* something like 10^(k-15) that we must resort to the Long
* calculation.
*/
char *
dtoa(double d0, int mode, int ndigits, int *decpt, int *sign, char **rve)
{
/* Arguments ndigits, decpt, sign are similar to those
of ecvt and fcvt; trailing zeros are suppressed from
the returned string. If not null, *rve is set to point
to the end of the return value. If d is +-Infinity or NaN,
then *decpt is set to 9999.
mode:
0 ==> shortest string that yields d when read in
and rounded to nearest.
1 ==> like 0, but with Steele & White stopping rule;
e.g. with IEEE P754 arithmetic , mode 0 gives
1e23 whereas mode 1 gives 9.999999999999999e22.
2 ==> max(1,ndigits) significant digits. This gives a
return value similar to that of ecvt, except
that trailing zeros are suppressed.
3 ==> through ndigits past the decimal point. This
gives a return value similar to that from fcvt,
except that trailing zeros are suppressed, and
ndigits can be negative.
4,5 ==> similar to 2 and 3, respectively, but (in
round-nearest mode) with the tests of mode 0 to
possibly return a shorter string that rounds to d.
With IEEE arithmetic and compilation with
-DHonor_FLT_ROUNDS, modes 4 and 5 behave the same
as modes 2 and 3 when FLT_ROUNDS != 1.
6-9 ==> Debugging modes similar to mode - 4: don't try
fast floating-point estimate (if applicable).
Values of mode other than 0-9 are treated as mode 0.
Sufficient space is allocated to the return value
to hold the suppressed trailing zeros.
*/
ThInfo *TI = 0;
int bbits, b2, b5, be, dig, i, ieps, ilim, ilim0, ilim1,
j, j1, k, k0, k_check, leftright, m2, m5, s2, s5,
spec_case, try_quick;
Long L;
int denorm;
ULong x;
Bigint *b, *b1, *delta, *mlo, *mhi, *S;
U d, d2, eps, eps1;
double ds;
char *s, *s0;
int Rounding;
Rounding = FLT_ROUNDS;
d.d = d0;
if (word0(&d) & Sign_bit) {
/* set sign for everything, including 0's and NaNs */
*sign = 1;
word0(&d) &= ~Sign_bit; /* clear sign bit */
}
else
*sign = 0;
if ((word0(&d) & Exp_mask) == Exp_mask)
{
/* Infinity or NaN */
*decpt = 9999;
if (!word1(&d) && !(word0(&d) & 0xfffff))
return __gdtoa_nrv_alloc("Infinity", rve, 8, &TI);
return __gdtoa_nrv_alloc("NaN", rve, 3, &TI);
}
if (!dval(&d)) {
*decpt = 1;
return __gdtoa_nrv_alloc("0", rve, 1, &TI);
}
if (Rounding >= 2) {
if (*sign)
Rounding = Rounding == 2 ? 0 : 2;
else
if (Rounding != 2)
Rounding = 0;
}
b = __gdtoa_d2b(dval(&d), &be, &bbits, &TI);
if (( i = (int)(word0(&d) >> Exp_shift1 & (Exp_mask>>Exp_shift1)) )!=0) {
dval(&d2) = dval(&d);
word0(&d2) &= Frac_mask1;
word0(&d2) |= Exp_11;
/* log(x) ~=~ log(1.5) + (x-1.5)/1.5
* log10(x) = log(x) / log(10)
* ~=~ log(1.5)/log(10) + (x-1.5)/(1.5*log(10))
* log10(&d) = (i-Bias)*log(2)/log(10) + log10(&d2)
*
* This suggests computing an approximation k to log10(&d) by
*
* k = (i - Bias)*0.301029995663981
* + ( (d2-1.5)*0.289529654602168 + 0.176091259055681 );
*
* We want k to be too large rather than too small.
* The error in the first-order Taylor series approximation
* is in our favor, so we just round up the constant enough
* to compensate for any error in the __gdtoa_multiplication of
* (i - Bias) by 0.301029995663981; since |i - Bias| <= 1077,
* and 1077 * 0.30103 * 2^-52 ~=~ 7.2e-14,
* adding 1e-13 to the constant term more than suffices.
* Hence we adjust the constant term to 0.1760912590558.
* (We could get a more accurate k by invoking log10,
* but this is probably not worthwhile.)
*/
i -= Bias;
denorm = 0;
}
else {
/* d is denormalized */
i = bbits + be + (Bias + (P-1) - 1);
x = i > 32 ? word0(&d) << (64 - i) | word1(&d) >> (i - 32)
: word1(&d) << (32 - i);
dval(&d2) = x;
word0(&d2) -= 31*Exp_msk1; /* adjust exponent */
i -= (Bias + (P-1) - 1) + 1;
denorm = 1;
}
ds = (dval(&d2)-1.5)*0.289529654602168 + 0.1760912590558 + i*0.301029995663981;
k = (int)ds;
if (ds < 0. && ds != k)
k--; /* want k = floor(ds) */
k_check = 1;
if (k >= 0 && k <= Ten_pmax) {
if (dval(&d) < __gdtoa_tens[k])
k--;
k_check = 0;
}
j = bbits - i - 1;
if (j >= 0) {
b2 = 0;
s2 = j;
}
else {
b2 = -j;
s2 = 0;
}
if (k >= 0) {
b5 = 0;
s5 = k;
s2 += k;
}
else {
b2 -= k;
b5 = -k;
s5 = 0;
}
if (mode < 0 || mode > 9)
mode = 0;
try_quick = Rounding == 1;
if (mode > 5) {
mode -= 4;
try_quick = 0;
}
leftright = 1;
ilim = ilim1 = -1; /* Values for cases 0 and 1; done here to */
/* silence erroneous "gcc -Wall" warning. */
switch(mode) {
case 0:
case 1:
i = 18;
ndigits = 0;
break;
case 2:
leftright = 0;
/* no break */
case 4:
if (ndigits <= 0)
ndigits = 1;
ilim = ilim1 = i = ndigits;
break;
case 3:
leftright = 0;
/* no break */
case 5:
i = ndigits + k + 1;
ilim = i;
ilim1 = i - 1;
if (i <= 0)
i = 1;
}
s = s0 = __gdtoa_rv_alloc(i, &TI);
if (mode > 1 && Rounding != 1)
leftright = 0;
if (ilim >= 0 && ilim <= Quick_max && try_quick) {
/* Try to get by with floating-point arithmetic. */
i = 0;
j1 = 0;
dval(&d2) = dval(&d);
k0 = k;
ilim0 = ilim;
ieps = 2; /* conservative */
if (k > 0) {
ds = __gdtoa_tens[k&0xf];
j = k >> 4;
if (j & Bletch) {
/* prevent overflows */
j &= Bletch - 1;
dval(&d) /= __gdtoa_bigtens[n___gdtoa_bigtens-1];
ieps++;
}
for(; j; j >>= 1, i++)
if (j & 1) {
ieps++;
ds *= __gdtoa_bigtens[i];
}
dval(&d) /= ds;
}
else if (( j1 = -k )!=0) {
dval(&d) *= __gdtoa_tens[j1 & 0xf];
for(j = j1 >> 4; j; j >>= 1, i++)
if (j & 1) {
ieps++;
dval(&d) *= __gdtoa_bigtens[i];
}
}
if (k_check && dval(&d) < 1. && ilim > 0) {
if (ilim1 <= 0)
goto fast_failed;
ilim = ilim1;
k--;
dval(&d) *= 10.;
ieps++;
}
dval(&eps) = ieps*dval(&d) + 7.;
word0(&eps) -= (P-1)*Exp_msk1;
if (ilim == 0) {
S = mhi = 0;
dval(&d) -= 5.;
if (dval(&d) > dval(&eps))
goto one_digit;
if (dval(&d) < -dval(&eps))
goto no_digits;
goto fast_failed;
}
if (leftright) {
/* Use Steele & White method of only
* generating digits needed.
*/
dval(&eps) = 0.5/__gdtoa_tens[ilim-1] - dval(&eps);
if (k0 < 0 && j1 >= 307) {
eps1.d = 1.01e256; /* 1.01 allows roundoff in the next few lines */
word0(&eps1) -= Exp_msk1 * (Bias+P-1);
dval(&eps1) *= __gdtoa_tens[j1 & 0xf];
for(i = 0, j = (j1-256) >> 4; j; j >>= 1, i++)
if (j & 1)
dval(&eps1) *= __gdtoa_bigtens[i];
if (eps.d < eps1.d)
eps.d = eps1.d;
if (10. - d.d < 10.*eps.d && eps.d < 1.) {
/* eps.d < 1. excludes trouble with the tiniest denormal */
*s++ = '1';
++k;
goto ret1;
}
}
for(i = 0;;) {
L = dval(&d);
dval(&d) -= L;
*s++ = '0' + (int)L;
if (dval(&d) < dval(&eps))
goto retc;
if (1. - dval(&d) < dval(&eps))
goto bump_up;
if (++i >= ilim)
break;
dval(&eps) *= 10.;
dval(&d) *= 10.;
}
}
else {
/* Generate ilim digits, then fix them up. */
dval(&eps) *= __gdtoa_tens[ilim-1];
for(i = 1;; i++, dval(&d) *= 10.) {
L = (Long)(dval(&d));
if (!(dval(&d) -= L))
ilim = i;
*s++ = '0' + (int)L;
if (i == ilim) {
if (dval(&d) > 0.5 + dval(&eps))
goto bump_up;
else if (dval(&d) < 0.5 - dval(&eps))
goto retc;
break;
}
}
}
fast_failed:
s = s0;
dval(&d) = dval(&d2);
k = k0;
ilim = ilim0;
}
/* Do we have a "small" integer? */
if (be >= 0 && k <= Int_max) {
/* Yes. */
ds = __gdtoa_tens[k];
if (ndigits < 0 && ilim <= 0) {
S = mhi = 0;
if (ilim < 0 || dval(&d) <= 5*ds)
goto no_digits;
goto one_digit;
}
for(i = 1;; i++, dval(&d) *= 10.) {
L = (Long)(dval(&d) / ds);
dval(&d) -= L*ds;
/* If FLT_ROUNDS == 2, L will usually be high by 1 */
if (dval(&d) < 0) {
L--;
dval(&d) += ds;
}
*s++ = '0' + (int)L;
if (!dval(&d)) {
break;
}
if (i == ilim) {
if (mode > 1)
switch(Rounding) {
case 0: goto retc;
case 2: goto bump_up;
}
dval(&d) += dval(&d);
if (dval(&d) > ds || (dval(&d) == ds && L & 1)) {
bump_up:
while(*--s == '9')
if (s == s0) {
k++;
*s = '0';
break;
}
++*s++;
}
break;
}
}
goto retc;
}
m2 = b2;
m5 = b5;
mhi = mlo = 0;
if (leftright) {
i = denorm ? be + (Bias + (P-1) - 1 + 1) : 1 + P - bbits;
b2 += i;
s2 += i;
mhi = __gdtoa_i2b(1, &TI);
}
if (m2 > 0 && s2 > 0) {
i = m2 < s2 ? m2 : s2;
b2 -= i;
m2 -= i;
s2 -= i;
}
if (b5 > 0) {
if (leftright) {
if (m5 > 0) {
mhi = __gdtoa_pow5mult(mhi, m5, &TI);
b1 = __gdtoa_mult(mhi, b, &TI);
__gdtoa_Bfree(b, &TI);
b = b1;
}
if (( j = b5 - m5 )!=0)
b = __gdtoa_pow5mult(b, j, &TI);
}
else
b = __gdtoa_pow5mult(b, b5, &TI);
}
S = __gdtoa_i2b(1, &TI);
if (s5 > 0)
S = __gdtoa_pow5mult(S, s5, &TI);
/* Check for special case that d is a normalized power of 2. */
spec_case = 0;
if ((mode < 2 || leftright) && Rounding == 1) {
if (!word1(&d) && !(word0(&d) & Bndry_mask) &&
word0(&d) & (Exp_mask & ~Exp_msk1)) {
/* The special case */
b2 += Log2P;
s2 += Log2P;
spec_case = 1;
}
}
/* Arrange for convenient computation of quotients:
* shift left if necessary so divisor has 4 leading 0 bits.
*
* Perhaps we should just compute leading 28 bits of S once
* and for all and pass them and a shift to __gdtoa_quorem, so it
* can do shifts and ors to compute the numerator for q.
*/
if (( i = ((s5 ? 32 - hi0bits(S->x[S->wds-1]) : 1) + s2) & 0x1f )!=0)
i = 32 - i;
if (i > 4) {
i -= 4;
b2 += i;
m2 += i;
s2 += i;
}
else if (i < 4) {
i += 28;
b2 += i;
m2 += i;
s2 += i;
}
if (b2 > 0)
b = __gdtoa_lshift(b, b2, &TI);
if (s2 > 0)
S = __gdtoa_lshift(S, s2, &TI);
if (k_check) {
if (__gdtoa_cmp(b,S) < 0) {
k--;
b = __gdtoa_multadd(b, 10, 0, &TI); /* we botched the k estimate */
if (leftright)
mhi = __gdtoa_multadd(mhi, 10, 0, &TI);
ilim = ilim1;
}
}
if (ilim <= 0 && (mode == 3 || mode == 5)) {
if (ilim < 0 || __gdtoa_cmp(b,S = __gdtoa_multadd(S,5,0,&TI)) <= 0) {
/* no digits, fcvt style */
no_digits:
k = -1 - ndigits;
goto ret;
}
one_digit:
*s++ = '1';
k++;
goto ret;
}
if (leftright) {
if (m2 > 0)
mhi = __gdtoa_lshift(mhi, m2, &TI);
/* Compute mlo -- check for special case
* that d is a normalized power of 2.
*/
mlo = mhi;
if (spec_case) {
mhi = __gdtoa_Balloc(mhi->k, &TI);
Bcopy(mhi, mlo);
mhi = __gdtoa_lshift(mhi, Log2P, &TI);
}
for(i = 1;;i++) {
dig = __gdtoa_quorem(b,S) + '0';
/* Do we yet have the shortest decimal string
* that will round to d?
*/
j = __gdtoa_cmp(b, mlo);
delta = __gdtoa_diff(S, mhi, &TI);
j1 = delta->sign ? 1 : __gdtoa_cmp(b, delta);
__gdtoa_Bfree(delta, &TI);
if (j1 == 0 && mode != 1 && !(word1(&d) & 1) && Rounding >= 1) {
if (dig == '9')
goto round_9_up;
if (j > 0)
dig++;
*s++ = dig;
goto ret;
}
if (j < 0 || (j == 0 && mode != 1 && !(word1(&d) & 1)
)) {
if (!b->x[0] && b->wds <= 1) {
goto accept_dig;
}
if (mode > 1)
switch(Rounding) {
case 0: goto accept_dig;
case 2: goto keep_dig;
}
if (j1 > 0) {
b = __gdtoa_lshift(b, 1, &TI);
j1 = __gdtoa_cmp(b, S);
if ((j1 > 0 || (j1 == 0 && dig & 1))
&& dig++ == '9')
goto round_9_up;
}
accept_dig:
*s++ = dig;
goto ret;
}
if (j1 > 0) {
if (!Rounding && mode > 1)
goto accept_dig;
if (dig == '9') { /* possible if i == 1 */
round_9_up:
*s++ = '9';
goto roundoff;
}
*s++ = dig + 1;
goto ret;
}
keep_dig:
*s++ = dig;
if (i == ilim)
break;
b = __gdtoa_multadd(b, 10, 0, &TI);
if (mlo == mhi)
mlo = mhi = __gdtoa_multadd(mhi, 10, 0, &TI);
else {
mlo = __gdtoa_multadd(mlo, 10, 0, &TI);
mhi = __gdtoa_multadd(mhi, 10, 0, &TI);
}
}
}
else {
for(i = 1;; i++) {
*s++ = dig = __gdtoa_quorem(b,S) + '0';
if (!b->x[0] && b->wds <= 1) {
goto ret;
}
if (i >= ilim)
break;
b = __gdtoa_multadd(b, 10, 0, &TI);
}
}
/* Round off last digit */
switch(Rounding) {
case 0: goto trimzeros;
case 2: goto roundoff;
}
b = __gdtoa_lshift(b, 1, &TI);
j = __gdtoa_cmp(b, S);
if (j > 0 || (j == 0 && dig & 1))
{
roundoff:
while(*--s == '9')
if (s == s0) {
k++;
*s++ = '1';
goto ret;
}
++*s++;
}
else {
trimzeros:
while(*--s == '0');
s++;
}
ret:
__gdtoa_Bfree(S, &TI);
if (mhi) {
if (mlo && mlo != mhi)
__gdtoa_Bfree(mlo, &TI);
__gdtoa_Bfree(mhi, &TI);
}
retc:
while(s > s0 && s[-1] == '0')
--s;
ret1:
__gdtoa_Bfree(b, &TI);
*s = 0;
*decpt = k + 1;
if (rve)
*rve = s;
return s0;
}