xref: /netbsd-src/lib/libc/gdtoa/strtodg.c (revision 9feb722ead58d8a751d6d81d917a158e180ce5c0)

/* $NetBSD: strtodg.c,v 1.13 2021/05/06 16:15:33 christos Exp $ */

/****************************************************************

The author of this software is David M. Gay.

Copyright (C) 1998-2001 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.

****************************************************************/

/* Please send bug reports to David M. Gay (dmg at acm dot org,
 * with " at " changed at "@" and " dot " changed to ".").	*/

#include "gdtoaimp.h"

#ifdef USE_LOCALE
#include "locale.h"
#endif

#ifndef VAX
 static CONST int
fivesbits[] = {	 0,  3,  5,  7, 10, 12, 14, 17, 19, 21,
		24, 26, 28, 31, 33, 35, 38, 40, 42, 45,
		47, 49, 52
		};
#endif

 Bigint *
#ifdef KR_headers
increment(b) Bigint *b;
#else
increment(Bigint *b)
#endif
{
	ULong *x, *xe;
	Bigint *b1;
#ifdef Pack_16
	ULong carry = 1, y;
#endif

	x = b->x;
	xe = x + b->wds;
#ifdef Pack_32
	do {
		if (*x < (ULong)0xffffffffL) {
			++*x;
			return b;
			}
		*x++ = 0;
		} while(x < xe);
#else
	do {
		y = *x + carry;
		carry = y >> 16;
		*x++ = y & 0xffff;
		if (!carry)
			return b;
		} while(x < xe);
	if (carry)
#endif
	{
		if (b->wds >= b->maxwds) {
			b1 = Balloc(b->k+1);
			if (b1 == NULL)
				return NULL;
			Bcopy(b1,b);
			Bfree(b);
			b = b1;
			}
		b->x[b->wds++] = 1;
		}
	return b;
	}

 void
#ifdef KR_headers
decrement(b) Bigint *b;
#else
decrement(Bigint *b)
#endif
{
	ULong *x, *xe;
#ifdef Pack_16
	ULong borrow = 1, y;
#endif

	x = b->x;
	xe = x + b->wds;
#ifdef Pack_32
	do {
		if (*x) {
			--*x;
			break;
			}
		*x++ = 0xffffffffUL;
		}
		while(x < xe);
#else
	do {
		y = *x - borrow;
		borrow = (y & 0x10000) >> 16;
		*x++ = y & 0xffff;
		} while(borrow && x < xe);
#endif
	}

 static int
#ifdef KR_headers
all_on(b, n) CONST Bigint *b; int n;
#else
all_on(CONST Bigint *b, int n)
#endif
{
	CONST ULong *x, *xe;

	x = b->x;
	xe = x + ((unsigned int)n >> kshift);
	while(x < xe)
		if ((*x++ & ALL_ON) != ALL_ON)
			return 0;
	if (n &= kmask)
		return ((*x | (ALL_ON << n)) & ALL_ON) == ALL_ON;
	return 1;
	}

 Bigint *
#ifdef KR_headers
set_ones(b, n) Bigint *b; int n;
#else
set_ones(Bigint *b, int n)
#endif
{
	int k;
	ULong *x, *xe;

	k = (unsigned int)(n + ((1 << kshift) - 1)) >> kshift;
	if (b->k < k) {
		Bfree(b);
		b = Balloc(k);
		if (b == NULL)
			return NULL;
		}
	k = (unsigned int)n >> kshift;
	if (n &= kmask)
		k++;
	b->wds = k;
	x = b->x;
	xe = x + k;
	while(x < xe)
		*x++ = ALL_ON;
	if (n)
		x[-1] >>= ULbits - n;
	return b;
	}

 static int
rvOK
#ifdef KR_headers
 (d, fpi, expt, bits, exact, rd, irv)
 U *d; CONST FPI *fpi; Long *expt; ULong *bits; int exact, rd, *irv;
#else
 (U *d, CONST FPI *fpi, Long *expt, ULong *bits, int exact, int rd, int *irv)
#endif
{
	Bigint *b;
	ULong carry, inex, lostbits;
	int bdif, e, j, k, k1, nb, rv;

	carry = rv = 0;
	b = d2b(dval(d), &e, &bdif);
	bdif -= nb = fpi->nbits;
	e += bdif;
	if (bdif <= 0) {
		if (exact)
			goto trunc;
		goto ret;
		}
	if (P == nb) {
		if (
#ifndef IMPRECISE_INEXACT
			exact &&
#endif
			fpi->rounding ==
#ifdef RND_PRODQUOT
					FPI_Round_near
#else
					Flt_Rounds
#endif
			) goto trunc;
		goto ret;
		}
	switch(rd) {
	  case 1: /* round down (toward -Infinity) */
		goto trunc;
	  case 2: /* round up (toward +Infinity) */
		break;
	  default: /* round near */
		k = bdif - 1;
		if (!k) {
			if (!exact)
				goto ret;
			if (b->x[0] & 2)
				break;
			goto trunc;
			}
		if (b->x[(unsigned int)k>>kshift] & ((ULong)1 << (k & kmask)))
			break;
		goto trunc;
	  }
	/* "break" cases: round up 1 bit, then truncate; bdif > 0 */
	carry = 1;
 trunc:
	inex = lostbits = 0;
	if (bdif > 0) {
		if ( (lostbits = any_on(b, bdif)) !=0)
			inex = STRTOG_Inexlo;
		rshift(b, bdif);
		if (carry) {
			inex = STRTOG_Inexhi;
			b = increment(b);
			if ( (j = nb & kmask) !=0)
				j = ULbits - j;
			if (hi0bits(b->x[b->wds - 1]) != j) {
				if (!lostbits)
					lostbits = b->x[0] & 1;
				rshift(b, 1);
				e++;
				}
			}
		}
	else if (bdif < 0) {
		b = lshift(b, -bdif);
		if (b == NULL)
			return STRTOG_NoMemory;
		}
	if (e < fpi->emin) {
		k = fpi->emin - e;
		e = fpi->emin;
		if (k > nb || fpi->sudden_underflow) {
			b->wds = inex = 0;
			*irv = STRTOG_Underflow | STRTOG_Inexlo;
			}
		else {
			k1 = k - 1;
			if (k1 > 0 && !lostbits)
				lostbits = any_on(b, k1);
			if (!lostbits && !exact)
				goto ret;
			lostbits |=
			  carry = b->x[(unsigned int)k1>>kshift] &
			               (1 << (k1 & kmask));
			rshift(b, k);
			*irv = STRTOG_Denormal;
			if (carry) {
				b = increment(b);
				inex = STRTOG_Inexhi | STRTOG_Underflow;
				}
			else if (lostbits)
				inex = STRTOG_Inexlo | STRTOG_Underflow;
			}
		}
	else if (e > fpi->emax) {
		e = fpi->emax + 1;
		*irv = STRTOG_Infinite | STRTOG_Overflow | STRTOG_Inexhi;
#ifndef NO_ERRNO
		errno = ERANGE;
#endif
		b->wds = inex = 0;
		}
	*expt = e;
	copybits(bits, nb, b);
	*irv |= inex;
	rv = 1;
 ret:
	Bfree(b);
	return rv;
	}

#ifndef VAX
 static int
#ifdef KR_headers
mantbits(d) U *d;
#else
mantbits(U *d)
#endif
{
	ULong L;
#ifdef VAX
	L = word1(d) << 16 | word1(d) >> 16;
	if (L)
#else
	if ( (L = word1(d)) !=0)
#endif
		return P - lo0bits(&L);
#ifdef VAX
	L = word0(d) << 16 | word0(d) >> 16 | Exp_msk11;
#else
	L = word0(d) | Exp_msk1;
#endif
	return P - 32 - lo0bits(&L);
	}
#endif /* !VAX */

 int
strtodg(CONST char *s00, char **se, CONST FPI *fpi, Long *expt, ULong *bits,
	locale_t loc)
{
	int abe, abits, asub;
#ifdef INFNAN_CHECK
	int decpt;
#endif
	int bb0, bb2, bb5, bbe, bd2, bd5, bbbits, bs2, c, denorm;
	int dsign, e, e1, e2, emin, esign, finished, i, inex, irv;
	int j, k, nbits, nd, nd0, nf, nz, nz0, rd, rvbits, rve, rve1, sign;
	int sudden_underflow = 0; /* pacify gcc */
	CONST char *s, *s0, *s1;
	double adj0, tol;
	Long L;
	U adj, rv;
	ULong *b, *be, y, z;
	Bigint *ab, *bb, *bb1, *bd, *bd0, *bs, *delta, *rvb, *rvb0;
#ifdef USE_LOCALE /*{{*/
	char *decimalpoint = localeconv_l(loc)->decimal_point;
	size_t dplen = strlen(decimalpoint);
#endif /*USE_LOCALE}}*/

	e2 = 0;	/* XXX gcc */

	irv = STRTOG_Zero;
	denorm = sign = nz0 = nz = 0;
	dval(&rv) = 0.;
	rvb = 0;
	nbits = fpi->nbits;
	for(s = s00;;s++) switch(*s) {
		case '-':
			sign = 1;
			/* FALLTHROUGH */
		case '+':
			if (*++s)
				goto break2;
			/* FALLTHROUGH */
		case 0:
			sign = 0;
			irv = STRTOG_NoNumber;
			s = s00;
			goto ret;
		case '\t':
		case '\n':
		case '\v':
		case '\f':
		case '\r':
		case ' ':
			continue;
		default:
			goto break2;
		}
 break2:
	if (*s == '0') {
#ifndef NO_HEX_FP
		switch(s[1]) {
		  case 'x':
		  case 'X':
			irv = gethex(&s, fpi, expt, &rvb, sign, loc);
			if (irv == STRTOG_NoNumber) {
				s = s00;
				sign = 0;
				}
			goto ret;
		  }
#endif
		nz0 = 1;
		while(*++s == '0') ;
		if (!*s)
			goto ret;
		}
	sudden_underflow = fpi->sudden_underflow;
	s0 = s;
	y = z = 0;
#ifdef INFNAN_CHECK
	decpt = 0;
#endif
	for(nd = nf = 0; (c = *s) >= '0' && c <= '9'; nd++, s++)
		if (nd < 9)
			y = 10*y + c - '0';
		else if (nd < 16)
			z = 10*z + c - '0';
	nd0 = nd;
#ifdef USE_LOCALE
	if (c == *decimalpoint) {
		for(i = 1; decimalpoint[i]; ++i)
			if (s[i] != decimalpoint[i])
				goto dig_done;
		s += i;
		c = *s;
#else
	if (c == '.') {
		c = *++s;
#endif
#ifdef INFNAN_CHECK
		decpt = 1;
#endif
		if (!nd) {
			for(; c == '0'; c = *++s)
				nz++;
			if (c > '0' && c <= '9') {
				s0 = s;
				nf += nz;
				nz = 0;
				goto have_dig;
				}
			goto dig_done;
			}
		for(; c >= '0' && c <= '9'; c = *++s) {
 have_dig:
			nz++;
			if (c -= '0') {
				nf += nz;
				for(i = 1; i < nz; i++)
					if (nd++ < 9)
						y *= 10;
					else if (nd <= DBL_DIG + 1)
						z *= 10;
				if (nd++ < 9)
					y = 10*y + c;
				else if (nd <= DBL_DIG + 1)
					z = 10*z + c;
				nz = 0;
				}
			}
		}/*}*/
 dig_done:
	e = 0;
	if (c == 'e' || c == 'E') {
		if (!nd && !nz && !nz0) {
			irv = STRTOG_NoNumber;
			s = s00;
			goto ret;
			}
		s00 = s;
		esign = 0;
		switch(c = *++s) {
			case '-':
				esign = 1;
				/* FALLTHROUGH */
			case '+':
				c = *++s;
			}
		if (c >= '0' && c <= '9') {
			while(c == '0')
				c = *++s;
			if (c > '0' && c <= '9') {
				L = c - '0';
				s1 = s;
				while((c = *++s) >= '0' && c <= '9')
					L = 10*L + c - '0';
				if (s - s1 > 8 || L > 19999)
					/* Avoid confusion from exponents
					 * so large that e might overflow.
					 */
					e = 19999; /* safe for 16 bit ints */
				else
					e = (int)L;
				if (esign)
					e = -e;
				}
			else
				e = 0;
			}
		else
			s = s00;
		}
	if (!nd) {
		if (!nz && !nz0) {
#ifdef INFNAN_CHECK
			/* Check for Nan and Infinity */
			if (!decpt)
			 switch(c) {
			  case 'i':
			  case 'I':
				if (match(&s,"nf")) {
					--s;
					if (!match(&s,"inity"))
						++s;
					irv = STRTOG_Infinite;
					goto infnanexp;
					}
				break;
			  case 'n':
			  case 'N':
				if (match(&s, "an")) {
					irv = STRTOG_NaN;
					*expt = fpi->emax + 1;
#ifndef No_Hex_NaN
					if (*s == '(') /*)*/
						irv = hexnan(&s, fpi, bits);
#endif
					goto infnanexp;
					}
			  }
#endif /* INFNAN_CHECK */
			irv = STRTOG_NoNumber;
			s = s00;
			}
		goto ret;
		}

	irv = STRTOG_Normal;
	e1 = e -= nf;
	rd = 0;
	switch(fpi->rounding & 3) {
	  case FPI_Round_up:
		rd = 2 - sign;
		break;
	  case FPI_Round_zero:
		rd = 1;
		break;
	  case FPI_Round_down:
		rd = 1 + sign;
	  }

	/* Now we have nd0 digits, starting at s0, followed by a
	 * decimal point, followed by nd-nd0 digits.  The number we're
	 * after is the integer represented by those digits times
	 * 10**e */

	if (!nd0)
		nd0 = nd;
	k = nd < DBL_DIG + 1 ? nd : DBL_DIG + 1;
	dval(&rv) = y;
	if (k > 9)
		dval(&rv) = tens[k - 9] * dval(&rv) + z;
	bd0 = 0;
	if (nbits <= P && nd <= DBL_DIG) {
		if (!e) {
			if (rvOK(&rv, fpi, expt, bits, 1, rd, &irv))
				goto ret;
			}
		else if (e > 0) {
			if (e <= Ten_pmax) {
#ifdef VAX
				goto vax_ovfl_check;
#else
				i = fivesbits[e] + mantbits(&rv) <= P;
				/* rv = */ rounded_product(dval(&rv), tens[e]);
				if (rvOK(&rv, fpi, expt, bits, i, rd, &irv))
					goto ret;
				e1 -= e;
				goto rv_notOK;
#endif
				}
			i = DBL_DIG - nd;
			if (e <= Ten_pmax + i) {
				/* A fancier test would sometimes let us do
				 * this for larger i values.
				 */
				e2 = e - i;
				e1 -= i;
				dval(&rv) *= tens[i];
#ifdef VAX
				/* VAX exponent range is so narrow we must
				 * worry about overflow here...
				 */
 vax_ovfl_check:
				dval(&adj) = dval(&rv);
				word0(&adj) -= P*Exp_msk1;
				/* adj = */ rounded_product(dval(&adj), tens[e2]);
				if ((word0(&adj) & Exp_mask)
				 > Exp_msk1*(DBL_MAX_EXP+Bias-1-P))
					goto rv_notOK;
				word0(&adj) += P*Exp_msk1;
				dval(&rv) = dval(&adj);
#else
				/* rv = */ rounded_product(dval(&rv), tens[e2]);
#endif
				if (rvOK(&rv, fpi, expt, bits, 0, rd, &irv))
					goto ret;
				e1 -= e2;
				}
			}
#ifndef Inaccurate_Divide
		else if (e >= -Ten_pmax) {
			/* rv = */ rounded_quotient(dval(&rv), tens[-e]);
			if (rvOK(&rv, fpi, expt, bits, 0, rd, &irv))
				goto ret;
			e1 -= e;
			}
#endif
		}
 rv_notOK:
	e1 += nd - k;

	/* Get starting approximation = rv * 10**e1 */

	e2 = 0;
	if (e1 > 0) {
		if ( (i = e1 & 15) !=0)
			dval(&rv) *= tens[i];
		if (e1 &= ~15) {
			e1 = (unsigned int)e1 >> 4;
			while(e1 >= (1 << (n_bigtens-1))) {
				e2 += ((word0(&rv) & Exp_mask)
					>> Exp_shift1) - Bias;
				word0(&rv) &= ~Exp_mask;
				word0(&rv) |= Bias << Exp_shift1;
				dval(&rv) *= bigtens[n_bigtens-1];
				e1 -= 1 << (n_bigtens-1);
				}
			e2 += ((word0(&rv) & Exp_mask) >> Exp_shift1) - Bias;
			word0(&rv) &= ~Exp_mask;
			word0(&rv) |= Bias << Exp_shift1;
			for(j = 0; e1 > 0; j++, e1 = (unsigned int)e1 >> 1)
				if (e1 & 1)
					dval(&rv) *= bigtens[j];
			}
		}
	else if (e1 < 0) {
		e1 = -e1;
		if ( (i = e1 & 15) !=0)
			dval(&rv) /= tens[i];
		if (e1 &= ~15) {
			e1 = (unsigned int)e1 >> 4;
			while(e1 >= (1 << (n_bigtens-1))) {
				e2 += ((word0(&rv) & Exp_mask)
					>> Exp_shift1) - Bias;
				word0(&rv) &= ~Exp_mask;
				word0(&rv) |= Bias << Exp_shift1;
				dval(&rv) *= tinytens[n_bigtens-1];
				e1 -= 1 << (n_bigtens-1);
				}
			e2 += ((word0(&rv) & Exp_mask) >> Exp_shift1) - Bias;
			word0(&rv) &= ~Exp_mask;
			word0(&rv) |= Bias << Exp_shift1;
			for(j = 0; e1 > 0; j++, e1 = (unsigned int)e1 >> 1)
				if (e1 & 1)
					dval(&rv) *= tinytens[j];
			}
		}
#ifdef IBM
	/* e2 is a correction to the (base 2) exponent of the return
	 * value, reflecting adjustments above to avoid overflow in the
	 * native arithmetic.  For native IBM (base 16) arithmetic, we
	 * must multiply e2 by 4 to change from base 16 to 2.
	 */
	e2 <<= 2;
#endif
	rvb = d2b(dval(&rv), &rve, &rvbits);	/* rv = rvb * 2^rve */
	if (rvb == NULL)
		return STRTOG_NoMemory;
	rve += e2;
	if ((j = rvbits - nbits) > 0) {
		rshift(rvb, j);
		rvbits = nbits;
		rve += j;
		}
	bb0 = 0;	/* trailing zero bits in rvb */
	e2 = rve + rvbits - nbits;
	if (e2 > fpi->emax + 1)
		goto huge;
	rve1 = rve + rvbits - nbits;
	if (e2 < (emin = fpi->emin)) {
		denorm = 1;
		j = rve - emin;
		if (j > 0) {
			rvb = lshift(rvb, j);
			if (rvb == NULL)
				return STRTOG_NoMemory;
			rvbits += j;
			}
		else if (j < 0) {
			rvbits += j;
			if (rvbits <= 0) {
				if (rvbits < -1) {
 ufl:
					rvb->wds = 0;
					rvb->x[0] = 0;
					*expt = emin;
					irv = STRTOG_Underflow | STRTOG_Inexlo;
					goto ret;
					}
				rvb->x[0] = rvb->wds = rvbits = 1;
				}
			else
				rshift(rvb, -j);
			}
		rve = rve1 = emin;
		if (sudden_underflow && e2 + 1 < emin)
			goto ufl;
		}

	/* Now the hard part -- adjusting rv to the correct value.*/

	/* Put digits into bd: true value = bd * 10^e */

	bd0 = s2b(s0, nd0, nd, y, dplen);

	for(;;) {
		bd = Balloc(bd0->k);
		if (bd == NULL)
			return STRTOG_NoMemory;
		Bcopy(bd, bd0);
		bb = Balloc(rvb->k);
		if (bb == NULL)
			return STRTOG_NoMemory;
		Bcopy(bb, rvb);
		bbbits = rvbits - bb0;
		bbe = rve + bb0;
		bs = i2b(1);
		if (bs == NULL)
			return STRTOG_NoMemory;

		if (e >= 0) {
			bb2 = bb5 = 0;
			bd2 = bd5 = e;
			}
		else {
			bb2 = bb5 = -e;
			bd2 = bd5 = 0;
			}
		if (bbe >= 0)
			bb2 += bbe;
		else
			bd2 -= bbe;
		bs2 = bb2;
		j = nbits + 1 - bbbits;
		i = bbe + bbbits - nbits;
		if (i < emin)	/* denormal */
			j += i - emin;
		bb2 += j;
		bd2 += j;
		i = bb2 < bd2 ? bb2 : bd2;
		if (i > bs2)
			i = bs2;
		if (i > 0) {
			bb2 -= i;
			bd2 -= i;
			bs2 -= i;
			}
		if (bb5 > 0) {
			bs = pow5mult(bs, bb5);
			if (bs == NULL)
				return STRTOG_NoMemory;
			bb1 = mult(bs, bb);
			if (bb1 == NULL)
				return STRTOG_NoMemory;
			Bfree(bb);
			bb = bb1;
			}
		bb2 -= bb0;
		if (bb2 > 0) {
			bb = lshift(bb, bb2);
			if (bb == NULL)
				return STRTOG_NoMemory;
			}
		else if (bb2 < 0)
			rshift(bb, -bb2);
		if (bd5 > 0) {
			bd = pow5mult(bd, bd5);
			if (bd == NULL)
				return STRTOG_NoMemory;
			}
		if (bd2 > 0) {
			bd = lshift(bd, bd2);
			if (bd == NULL)
				return STRTOG_NoMemory;
			}
		if (bs2 > 0) {
			bs = lshift(bs, bs2);
			if (bs == NULL)
				return STRTOG_NoMemory;
			}
		asub = 1;
		inex = STRTOG_Inexhi;
		delta = diff(bb, bd);
		if (delta == NULL)
			return STRTOG_NoMemory;
		if (delta->wds <= 1 && !delta->x[0])
			break;
		dsign = delta->sign;
		delta->sign = finished = 0;
		L = 0;
		i = cmp(delta, bs);
		if (rd && i <= 0) {
			irv = STRTOG_Normal;
			if ( (finished = dsign ^ (rd&1)) !=0) {
				if (dsign != 0) {
					irv |= STRTOG_Inexhi;
					goto adj1;
					}
				irv |= STRTOG_Inexlo;
				if (rve1 == emin)
					goto adj1;
				for(i = 0, j = nbits; j >= ULbits;
						i++, j -= ULbits) {
					if (rvb->x[i] & ALL_ON)
						goto adj1;
					}
				if (j > 1 && lo0bits(rvb->x + i) < j - 1)
					goto adj1;
				rve = rve1 - 1;
				rvb = set_ones(rvb, rvbits = nbits);
				if (rvb == NULL)
					return STRTOG_NoMemory;
				break;
				}
			irv |= dsign ? STRTOG_Inexlo : STRTOG_Inexhi;
			break;
			}
		if (i < 0) {
			/* Error is less than half an ulp -- check for
			 * special case of mantissa a power of two.
			 */
			irv = dsign
				? STRTOG_Normal | STRTOG_Inexlo
				: STRTOG_Normal | STRTOG_Inexhi;
			if (dsign || bbbits > 1 || denorm || rve1 == emin)
				break;
			delta = lshift(delta,1);
			if (delta == NULL)
				return STRTOG_NoMemory;
			if (cmp(delta, bs) > 0) {
				irv = STRTOG_Normal | STRTOG_Inexlo;
				goto drop_down;
				}
			break;
			}
		if (i == 0) {
			/* exactly half-way between */
			if (dsign) {
				if (denorm && all_on(rvb, rvbits)) {
					/*boundary case -- increment exponent*/
					rvb->wds = 1;
					rvb->x[0] = 1;
					rve = emin + nbits - (rvbits = 1);
					irv = STRTOG_Normal | STRTOG_Inexhi;
					denorm = 0;
					break;
					}
				irv = STRTOG_Normal | STRTOG_Inexlo;
				}
			else if (bbbits == 1) {
				irv = STRTOG_Normal;
 drop_down:
				/* boundary case -- decrement exponent */
				if (rve1 == emin) {
					irv = STRTOG_Normal | STRTOG_Inexhi;
					if (rvb->wds == 1 && rvb->x[0] == 1)
						sudden_underflow = 1;
					break;
					}
				rve -= nbits;
				rvb = set_ones(rvb, rvbits = nbits);
				if (rvb == NULL)
					return STRTOG_NoMemory;
				break;
				}
			else
				irv = STRTOG_Normal | STRTOG_Inexhi;
			if ((bbbits < nbits && !denorm) || !(rvb->x[0] & 1))
				break;
			if (dsign) {
				rvb = increment(rvb);
				if (rvb == NULL)
					return STRTOG_NoMemory;
				j = kmask & (ULbits - (rvbits & kmask));
				if (hi0bits(rvb->x[rvb->wds - 1]) != j)
					rvbits++;
				irv = STRTOG_Normal | STRTOG_Inexhi;
				}
			else {
				if (bbbits == 1)
					goto undfl;
				decrement(rvb);
				irv = STRTOG_Normal | STRTOG_Inexlo;
				}
			break;
			}
		if ((dval(&adj) = ratio(delta, bs)) <= 2.) {
 adj1:
			inex = STRTOG_Inexlo;
			if (dsign) {
				asub = 0;
				inex = STRTOG_Inexhi;
				}
			else if (denorm && bbbits <= 1) {
 undfl:
				rvb->wds = 0;
				rve = emin;
				irv = STRTOG_Underflow | STRTOG_Inexlo;
				break;
				}
			adj0 = dval(&adj) = 1.;
			}
		else {
			adj0 = dval(&adj) *= 0.5;
			if (dsign) {
				asub = 0;
				inex = STRTOG_Inexlo;
				}
			if (dval(&adj) < 2147483647.) {
				L = adj0;
				adj0 -= L;
				switch(rd) {
				  case 0:
					if (adj0 >= .5)
						goto inc_L;
					break;
				  case 1:
					if (asub && adj0 > 0.)
						goto inc_L;
					break;
				  case 2:
					if (!asub && adj0 > 0.) {
 inc_L:
						L++;
						inex = STRTOG_Inexact - inex;
						}
				  }
				dval(&adj) = L;
				}
			}
		y = rve + rvbits;

		/* adj *= ulp(dval(&rv)); */
		/* if (asub) rv -= adj; else rv += adj; */

		if (!denorm && rvbits < nbits) {
			rvb = lshift(rvb, j = nbits - rvbits);
			if (rvb == NULL)
				return STRTOG_NoMemory;
			rve -= j;
			rvbits = nbits;
			}
		ab = d2b(dval(&adj), &abe, &abits);
		if (ab == NULL)
			return STRTOG_NoMemory;
		if (abe < 0)
			rshift(ab, -abe);
		else if (abe > 0) {
			ab = lshift(ab, abe);
			if (ab == NULL)
				return STRTOG_NoMemory;
			}
		rvb0 = rvb;
		if (asub) {
			/* rv -= adj; */
			j = hi0bits(rvb->x[rvb->wds-1]);
			rvb = diff(rvb, ab);
			if (rvb == NULL)
				return STRTOG_NoMemory;
			k = rvb0->wds - 1;
			if (denorm)
				/* do nothing */;
			else if (rvb->wds <= k
				|| hi0bits( rvb->x[k]) >
				   hi0bits(rvb0->x[k])) {
				/* unlikely; can only have lost 1 high bit */
				if (rve1 == emin) {
					--rvbits;
					denorm = 1;
					}
				else {
					rvb = lshift(rvb, 1);
					if (rvb == NULL)
						return STRTOG_NoMemory;
					--rve;
					--rve1;
					L = finished = 0;
					}
				}
			}
		else {
			rvb = sum(rvb, ab);
			if (rvb == NULL)
				return STRTOG_NoMemory;
			k = rvb->wds - 1;
			if (k >= rvb0->wds
			 || hi0bits(rvb->x[k]) < hi0bits(rvb0->x[k])) {
				if (denorm) {
					if (++rvbits == nbits)
						denorm = 0;
					}
				else {
					rshift(rvb, 1);
					rve++;
					rve1++;
					L = 0;
					}
				}
			}
		Bfree(ab);
		Bfree(rvb0);
		if (finished)
			break;

		z = rve + rvbits;
		if (y == z && L) {
			/* Can we stop now? */
			tol = dval(&adj) * 5e-16; /* > max rel error */
			dval(&adj) = adj0 - .5;
			if (dval(&adj) < -tol) {
				if (adj0 > tol) {
					irv |= inex;
					break;
					}
				}
			else if (dval(&adj) > tol && adj0 < 1. - tol) {
				irv |= inex;
				break;
				}
			}
		bb0 = denorm ? 0 : trailz(rvb);
		Bfree(bb);
		Bfree(bd);
		Bfree(bs);
		Bfree(delta);
		}
	if (!denorm && (j = nbits - rvbits)) {
		if (j > 0) {
			rvb = lshift(rvb, j);
			if (rvb == NULL)
				return STRTOG_NoMemory;
			}
		else
			rshift(rvb, -j);
		rve -= j;
		}
	*expt = rve;
	Bfree(bb);
	Bfree(bd);
	Bfree(bs);
	Bfree(bd0);
	Bfree(delta);
	if (rve > fpi->emax) {
		switch(fpi->rounding & 3) {
		  case FPI_Round_near:
			goto huge;
		  case FPI_Round_up:
			if (!sign)
				goto huge;
			break;
		  case FPI_Round_down:
			if (sign)
				goto huge;
		  }
		/* Round to largest representable magnitude */
		Bfree(rvb);
		rvb = 0;
		irv = STRTOG_Normal | STRTOG_Inexlo;
		*expt = fpi->emax;
		b = bits;
		be = b + ((unsigned int)(fpi->nbits + 31) >> 5);
		while(b < be)
			*b++ = (unsigned int)-1;
		if ((j = fpi->nbits & 0x1f) != 0)
			*--be >>= (32 - j);
		goto ret;
 huge:
		rvb->wds = 0;
		irv = STRTOG_Infinite | STRTOG_Overflow | STRTOG_Inexhi;
#ifndef NO_ERRNO
		errno = ERANGE;
#endif
#ifdef INFNAN_CHECK
 infnanexp:
#endif
		*expt = fpi->emax + 1;
		}
 ret:
	if (denorm) {
		if (sudden_underflow) {
			rvb->wds = 0;
			irv = STRTOG_Underflow | STRTOG_Inexlo;
#ifndef NO_ERRNO
			errno = ERANGE;
#endif
			}
		else  {
			irv = (irv & ~STRTOG_Retmask) |
				(rvb->wds > 0 ? STRTOG_Denormal : STRTOG_Zero);
			if (irv & STRTOG_Inexact) {
				irv |= STRTOG_Underflow;
#ifndef NO_ERRNO
				errno = ERANGE;
#endif
				}
			}
		}
	if (se)
		*se = __UNCONST(s);
	if (sign)
		irv |= STRTOG_Neg;
	if (rvb) {
		copybits(bits, nbits, rvb);
		Bfree(rvb);
		}
	return irv;
	}