floatconv.c

早期freebsd实现

                        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
_Xstrtod
#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;
	TEST_ENDIANNESS;
        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:
                        goto ret;
                case '\t':
                case '\n':
                case '\v':
                case '\f':
                case '\r':
                case ' ':
                        continue;
                default:
                        goto break2;
                }
 break2:
        if (*s == '0') {
                nz0 = 1;
                while(*++s == '0') ;
                if (!*s)
                        goto ret;
                }
        s0 = s;
        y = z = 0;
        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;
        if (c == '.') {
                c = *++s;
                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) {
                        s = s00;
                        goto ret;
                        }
                s00 = s;
                esign = 0;
                switch(c = *++s) {
                        case '-':
                                esign = 1;
                        case '+':
                                c = *++s;
                        }
                if (c >= '0' && c <= '9') {
                        while(c == '0')
                                c = *++s;
                        if (c > '0' && c <= '9') {
                                e = c - '0';
                                s1 = s;
                                while((c = *++s) >= '0' && c <= '9')
                                        e = 10*e + c - '0';
                                if (s - s1 > 8)
                                        /* Avoid confusion from exponents
                                         * so large that e might overflow.
                                         */
                                        e = 9999999;
                                if (esign)
                                        e = -e;
                                }
                        else
                                e = 0;
                        }
                else
                        s = s00;
                }
        if (!nd) {
                if (!nz && !nz0)
                        s = s00;
                goto ret;
                }
        e1 = e -= nf;

        /* 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;
        rv = y;
        if (k > 9)
                rv = tens[k - 9] * rv + z;
        if (nd <= DBL_DIG