strtod.c

早期freebsd实现

	}
	k = a->k;
	wa = a->wds;
	wb = b->wds;
	wc = wa + wb;
	if (wc > a->maxwds)
		k++;
	c = Balloc(k);
	for (x = c->x, xa = x + wc; x < xa; x++)
		*x = 0;
	xa = a->x;
	xae = xa + wa;
	xb = b->x;
	xbe = xb + wb;
	xc0 = c->x;
#ifdef Pack_32
	for (; xb < xbe; xb++, xc0++) {
		if (y = *xb & 0xffff) {
			x = xa;
			xc = xc0;
			carry = 0;
			do {
				z = (*x & 0xffff) * y + (*xc & 0xffff) + carry;
				carry = z >> 16;
				z2 = (*x++ >> 16) * y + (*xc >> 16) + carry;
				carry = z2 >> 16;
				Storeinc(xc, z2, z);
			} while (x < xae);
			*xc = carry;
		}
		if (y = *xb >> 16) {
			x = xa;
			xc = xc0;
			carry = 0;
			z2 = *xc;
			do {
				z = (*x & 0xffff) * y + (*xc >> 16) + carry;
				carry = z >> 16;
				Storeinc(xc, z, z2);
				z2 = (*x++ >> 16) * y + (*xc & 0xffff) + carry;
				carry = z2 >> 16;
			} while (x < xae);
			*xc = z2;
		}
	}
#else
	for (; xb < xbe; xc0++) {
		if (y = *xb++) {
			x = xa;
			xc = xc0;
			carry = 0;
			do {
				z = *x++ * y + *xc + carry;
				carry = z >> 16;
				*xc++ = z & 0xffff;
			} while (x < xae);
			*xc = carry;
		}
	}
#endif
	for (xc0 = c->x, xc = xc0 + wc; wc > 0 && !*--xc; --wc) ;
	c->wds = wc;
	return c;
}

 static Bigint *p5s;

 static Bigint *
pow5mult
#ifdef KR_headers
	(b, k) Bigint *b; int k;
#else
	(Bigint *b, int k)
#endif
{
	Bigint *b1, *p5, *p51;
	int i;
	static int p05[3] = { 5, 25, 125 };

	if (i = k & 3)
		b = multadd(b, p05[i-1], 0);

	if (!(k >>= 2))
		return b;
	if (!(p5 = p5s)) {
		/* first time */
		p5 = p5s = i2b(625);
		p5->next = 0;
	}
	for (;;) {
		if (k & 1) {
			b1 = mult(b, p5);
			Bfree(b);
			b = b1;
		}
		if (!(k >>= 1))
			break;
		if (!(p51 = p5->next)) {
			p51 = p5->next = mult(p5,p5);
			p51->next = 0;
		}
		p5 = p51;
	}
	return b;
}

 static Bigint *
lshift
#ifdef KR_headers
	(b, k) Bigint *b; int k;
#else
	(Bigint *b, int k)
#endif
{
	int i, k1, n, n1;
	Bigint *b1;
	unsigned long *x, *x1, *xe, z;

#ifdef Pack_32
	n = k >> 5;
#else
	n = k >> 4;
#endif
	k1 = b->k;
	n1 = n + b->wds + 1;
	for (i = b->maxwds; n1 > i; i <<= 1)
		k1++;
	b1 = Balloc(k1);
	x1 = b1->x;
	for (i = 0; i < n; i++)
		*x1++ = 0;
	x = b->x;
	xe = x + b->wds;
#ifdef Pack_32
	if (k &= 0x1f) {
		k1 = 32 - k;
		z = 0;
		do {
			*x1++ = *x << k | z;
			z = *x++ >> k1;
		} while (x < xe);
		if (*x1 = z)
			++n1;
	}
#else
	if (k &= 0xf) {
		k1 = 16 - k;
		z = 0;
		do {
			*x1++ = *x << k  & 0xffff | z;
			z = *x++ >> k1;
		} while (x < xe);
		if (*x1 = z)
			++n1;
	}
#endif
	else
		do
			*x1++ = *x++;
		while (x < xe);
	b1->wds = n1 - 1;
	Bfree(b);
	return b1;
}

 static int
cmp
#ifdef KR_headers
	(a, b) Bigint *a, *b;
#else
	(Bigint *a, Bigint *b)
#endif
{
	unsigned long *xa, *xa0, *xb, *xb0;
	int i, j;

	i = a->wds;
	j = b->wds;
#ifdef DEBUG
	if (i > 1 && !a->x[i-1])
		Bug("cmp called with a->x[a->wds-1] == 0");
	if (j > 1 && !b->x[j-1])
		Bug("cmp called with b->x[b->wds-1] == 0");
#endif
	if (i -= j)
		return i;
	xa0 = a->x;
	xa = xa0 + j;
	xb0 = b->x;
	xb = xb0 + j;
	for (;;) {
		if (*--xa != *--xb)
			return *xa < *xb ? -1 : 1;
		if (xa <= xa0)
			break;
	}
	return 0;
}

 static Bigint *
diff
#ifdef KR_headers
	(a, b) Bigint *a, *b;
#else
	(Bigint *a, Bigint *b)
#endif
{
	Bigint *c;
	int i, wa, wb;
	long borrow, y;	/* We need signed shifts here. */
	unsigned long *xa, *xae, *xb, *xbe, *xc;
#ifdef Pack_32
	long z;
#endif

	i = cmp(a,b);
	if (!i) {
		c = Balloc(0);
		c->wds = 1;
		c->x[0] = 0;
		return c;
	}
	if (i < 0) {
		c = a;
		a = b;
		b = c;
		i = 1;
	} else
		i = 0;
	c = Balloc(a->k);
	c->sign = i;
	wa = a->wds;
	xa = a->x;
	xae = xa + wa;
	wb = b->wds;
	xb = b->x;
	xbe = xb + wb;
	xc = c->x;
	borrow = 0;
#ifdef Pack_32
	do {
		y = (*xa & 0xffff) - (*xb & 0xffff) + borrow;
		borrow = y >> 16;
		Sign_Extend(borrow, y);
		z = (*xa++ >> 16) - (*xb++ >> 16) + borrow;
		borrow = z >> 16;
		Sign_Extend(borrow, z);
		Storeinc(xc, z, y);
	} while (xb < xbe);
	while (xa < xae) {
		y = (*xa & 0xffff) + borrow;
		borrow = y >> 16;
		Sign_Extend(borrow, y);
		z = (*xa++ >> 16) + borrow;
		borrow = z >> 16;
		Sign_Extend(borrow, z);
		Storeinc(xc, z, y);
	}
#else
	do {
		y = *xa++ - *xb++ + borrow;
		borrow = y >> 16;
		Sign_Extend(borrow, y);
		*xc++ = y & 0xffff;
	} while (xb < xbe);
	while (xa < xae) {
		y = *xa++ + borrow;
		borrow = y >> 16;
		Sign_Extend(borrow, y);
		*xc++ = y & 0xffff;
	}
#endif
	while (!*--xc)
		wa--;
	c->wds = wa;
	return c;
}

 static double
ulp
#ifdef KR_headers
	(x) double x;
#else
	(double x)
#endif
{
	register long L;
	double a;

	L = (word0(x) & Exp_mask) - (P-1)*Exp_msk1;
#ifndef Sudden_Underflow
	if (L > 0) {
#endif
#ifdef IBM
		L |= Exp_msk1 >> 4;
#endif
		word0(a) = L;
		word1(a) = 0;
#ifndef Sudden_Underflow
	} else {
		L = -L >> Exp_shift;
		if (L < Exp_shift) {
			word0(a) = 0x80000 >> L;
			word1(a) = 0;
		} else {
			word0(a) = 0;
			L -= Exp_shift;
			word1(a) = L >= 31 ? 1 : 1 << 31 - L;
		}
	}
#endif
	return a;
}

 static double
b2d
#ifdef KR_headers
	(a, e) Bigint *a; int *e;
#else
	(Bigint *a, int *e)
#endif
{
	unsigned long *xa, *xa0, w, y, z;
	int k;
	double d;
#ifdef VAX
	unsigned long d0, d1;
#else
#define d0 word0(d)
#define d1 word1(d)
#endif

	xa0 = a->x;
	xa = xa0 + a->wds;
	y = *--xa;
#ifdef DEBUG
	if (!y) Bug("zero y in b2d");
#endif
	k = hi0bits(y);
	*e = 32 - k;
#ifdef Pack_32
	if (k < Ebits) {
		d0 = Exp_1 | y >> Ebits - k;
		w = xa > xa0 ? *--xa : 0;
		d1 = y << (32-Ebits) + k | w >> Ebits - k;
		goto ret_d;
		}
	z = xa > xa0 ? *--xa : 0;
	if (k -= Ebits) {
		d0 = Exp_1 | y << k | z >> 32 - k;
		y = xa > xa0 ? *--xa : 0;
		d1 = z << k | y >> 32 - k;
	} else {
		d0 = Exp_1 | y;
		d1 = z;
	}
#else
	if (k < Ebits + 16) {
		z = xa > xa0 ? *--xa : 0;
		d0 = Exp_1 | y << k - Ebits | z >> Ebits + 16 - k;
		w = xa > xa0 ? *--xa : 0;
		y = xa > xa0 ? *--xa : 0;
		d1 = z << k + 16 - Ebits | w << k - Ebits | y >> 16 + Ebits - k;
		goto ret_d;
	}
	z = xa > xa0 ? *--xa : 0;
	w = xa > xa0 ? *--xa : 0;
	k -= Ebits + 16;
	d0 = Exp_1 | y << k + 16 | z << k | w >> 16 - k;
	y = xa > xa0 ? *--xa : 0;
	d1 = w << k + 16 | y << k;
#endif
 ret_d:
#ifdef VAX
	word0(d) = d0 >> 16 | d0 << 16;
	word1(d) = d1 >> 16 | d1 << 16;
#else
#undef d0
#undef d1
#endif
	return d;
}

 static Bigint *
d2b
#ifdef KR_headers
	(d, e, bits) double d; int *e, *bits;
#else
	(double d, int *e, int *bits)
#endif
{
	Bigint *b;
	int de, i, k;
	unsigned long *x, y, z;
#ifdef VAX
	unsigned long d0, d1;
	d0 = word0(d) >> 16 | word0(d) << 16;
	d1 = word1(d) >> 16 | word1(d) << 16;
#else
#define d0 word0(d)
#define d1 word1(d)
#endif

#ifdef Pack_32
	b = Balloc(1);
#else
	b = Balloc(2);
#endif
	x = b->x;

	z = d0 & Frac_mask;
	d0 &= 0x7fffffff;	/* clear sign bit, which we ignore */
#ifdef Sudden_Underflow
	de = (int)(d0 >> Exp_shift);
#ifndef IBM
	z |= Exp_msk11;
#endif
#else
	if (de = (int)(d0 >> Exp_shift))
		z |= Exp_msk1;
#endif
#ifdef Pack_32
	if (y = d1) {
		if (k = lo0bits(&y)) {
			x[0] = y | z << 32 - k;
			z >>= k;
			}
		else
			x[0] = y;
		i = b->wds = (x[1] = z) ? 2 : 1;
	} else {
#ifdef DEBUG
		if (!z)
			Bug("Zero passed to d2b");
#endif
		k = lo0bits(&z);
		x[0] = z;
		i = b->wds = 1;
		k += 32;
	}
#else
	if (y = d1) {
		if (k = lo0bits(&y))
			if (k >= 16) {
				x[0] = y | z << 32 - k & 0xffff;
				x[1] = z >> k - 16 & 0xffff;
				x[2] = z >> k;
				i = 2;
			} else {
				x[0] = y & 0xffff;
				x[1] = y >> 16 | z << 16 - k & 0xffff;
				x[2] = z >> k & 0xffff;
				x[3] = z >> k+16;
				i = 3;
			}
		else {
			x[0] = y & 0xffff;
			x[1] = y >> 16;
			x[2] = z & 0xffff;
			x[3] = z >> 16;
			i = 3;
		}
	} else {
#ifdef DEBUG
		if (!z)
			Bug("Zero passed to d2b");
#endif
		k = lo0bits(&z);
		if (k >= 16) {
			x[0] = z;
			i = 0;
		} else {
			x[0] = z & 0xffff;
			x[1] = z >> 16;
			i = 1;
		}
		k += 32;
	}
	while (!x[i])
		--i;
	b->wds = i + 1;
#endif
#ifndef Sudden_Underflow
	if (de) {
#endif
#ifdef IBM
		*e = (de - Bias - (P-1) << 2) + k;
		*bits = 4*P + 8 - k - hi0bits(word0(d) & Frac_mask);
#else
		*e = de - Bias - (P-1) + k;
		*bits = P - k;
#endif
#ifndef Sudden_Underflow
	} else {
		*e = de - Bias - (P-1) + 1 + k;
#ifdef Pack_32
		*bits = 32*i - hi0bits(x[i-1]);
#else
		*bits = (i+2)*16 - hi0bits(x[i]);
#endif
	}
#endif
	return b;
}
#undef d0
#undef d1

 static double
ratio
#ifdef KR_headers
	(a, b) Bigint *a, *b;
#else
	(Bigint *a, Bigint *b)
#endif
{
	double da, db;
	int k, ka, kb;

	da = b2d(a, &ka);
	db = b2d(b, &kb);
#ifdef Pack_32
	k = ka - kb + 32*(a->wds - b->wds);
#else
	k = ka - kb + 16*(a->wds - b->wds);
#endif
#ifdef IBM
	if (k > 0) {
		word0(da) += (k >> 2)*Exp_msk1;
		if (k &= 3)
			da *= 1 << k;
	} else {
		k = -k;
		word0(db) += (k >> 2)*Exp_msk1;
		if (k &= 3)
			db *= 1 << k;
	}
#else
	if (k > 0)
		word0(da) += k*Exp_msk1;
	else {
		k = -k;
		word0(db) += k*Exp_msk1;
	}
#endif
	return da / db;
}

 static double
tens[] = {
		1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9,
		1e10, 1e11, 1e12, 1e13, 1e14, 1e15, 1e16, 1e17, 1e18, 1e19,
		1e20, 1e21, 1e22
#ifdef VAX
		, 1e23, 1e24
#endif
		};

 static double
#ifdef IEEE_Arith
bigtens[] = { 1e16, 1e32, 1e64, 1e128, 1e256 };
static double tinytens[] = { 1e-16, 1e-32, 1e-64, 1e-128, 1e-256 };
#define n_bigtens 5
#else
#ifdef IBM
bigtens[] = { 1e16, 1e32, 1e64 };
static double tinytens[] = { 1e-16, 1e-32, 1e-64 };
#define n_bigtens 3
#else
bigtens[] = { 1e16, 1e32 };
static double tinytens[] = { 1e-16, 1e-32 };
#define n_bigtens 2
#endif
#endif

 double
strtod
#ifdef KR_headers
	(s00, se) CONST char *s00; char **se;
#else
	(CONST char *s00, char **se)
#endif
{
	int bb2, bb5, bbe, bd2, bd5, bbbits, bs2, c, dsign,
		 e, e1, esign, i, j, k, nd, nd0, nf, nz, nz0, sign;
	CONST char *s, *s0, *s1;
	double aadj, aadj1, adj, rv, rv0;
	long L;
	unsigned long y, z;
	Bigint *bb, *bb1, *bd, *bd0, *bs, *delta;
	sign = nz0 = nz = 0;
	rv = 0.;
	for (s = s00;;s++) switch(*s) {
		case '-':
			sign = 1;
			/* no break */
		case '+':
			if (*++s)
				goto break2;
			/* no break */
		case 0:
			s = s00;
			goto ret;
		case '\t':
		case '\n':
		case '\v':
		case '\f':
		case '\r':
		case ' ':
			continue;
		default:
			goto break2;
	}