dtoa.cpp

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#endif
    if (k > 0)
        word0(da) += k * Exp_msk1;
    else {
        k = -k;
        word0(db) += k * Exp_msk1;
    }
    return dval(da) / dval(db);
}

static const 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
};

static const double bigtens[] = { 1e16, 1e32, 1e64, 1e128, 1e256 };
static const double tinytens[] = { 1e-16, 1e-32, 1e-64, 1e-128,
#ifdef Avoid_Underflow
        9007199254740992. * 9007199254740992.e-256
        /* = 2^106 * 1e-53 */
#else
        1e-256
#endif
};

/* The factor of 2^53 in tinytens[4] helps us avoid setting the underflow */
/* flag unnecessarily.  It leads to a song and dance at the end of strtod. */
#define Scale_Bit 0x10
#define n_bigtens 5

#if defined(INFNAN_CHECK)

#ifndef NAN_WORD0
#define NAN_WORD0 0x7ff80000
#endif

#ifndef NAN_WORD1
#define NAN_WORD1 0
#endif

static int match(const char** sp, const char* t)
{
    int c, d;
    const char* s = *sp;

    while ((d = *t++)) {
        if ((c = *++s) >= 'A' && c <= 'Z')
            c += 'a' - 'A';
        if (c != d)
            return 0;
    }
    *sp = s + 1;
    return 1;
}

#ifndef No_Hex_NaN
static void hexnan(double* rvp, const char** sp)
{
    uint32_t c, x[2];
    const char* s;
    int havedig, udx0, xshift;

    x[0] = x[1] = 0;
    havedig = xshift = 0;
    udx0 = 1;
    s = *sp;
    while ((c = *(const unsigned char*)++s)) {
        if (c >= '0' && c <= '9')
            c -= '0';
        else if (c >= 'a' && c <= 'f')
            c += 10 - 'a';
        else if (c >= 'A' && c <= 'F')
            c += 10 - 'A';
        else if (c <= ' ') {
            if (udx0 && havedig) {
                udx0 = 0;
                xshift = 1;
            }
            continue;
        } else if (/*(*/ c == ')' && havedig) {
            *sp = s + 1;
            break;
        } else
            return;    /* invalid form: don't change *sp */
        havedig = 1;
        if (xshift) {
            xshift = 0;
            x[0] = x[1];
            x[1] = 0;
        }
        if (udx0)
            x[0] = (x[0] << 4) | (x[1] >> 28);
        x[1] = (x[1] << 4) | c;
    }
    if ((x[0] &= 0xfffff) || x[1]) {
        word0(*rvp) = Exp_mask | x[0];
        word1(*rvp) = x[1];
    }
}
#endif /*No_Hex_NaN*/
#endif /* INFNAN_CHECK */

double strtod(const char* s00, char** se)
{
#ifdef Avoid_Underflow
    int scale;
#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;
    int32_t L;
    uint32_t y, z;
    Bigint *bb = NULL, *bb1 = NULL, *bd = NULL, *bd0 = NULL, *bs = NULL, *delta = NULL;
#ifdef SET_INEXACT
    int inexact, oldinexact;
#endif

    sign = nz0 = nz = 0;
    dval(rv) = 0.;
    for (s = s00; ; s++)
        switch (*s) {
            case '-':
                sign = 1;
                /* no break */
            case '+':
                if (*++s)
                    goto break2;
                /* no break */
            case 0:
                goto ret0;
            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) {
            goto ret0;
        }
        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') {
                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 */
            switch(c) {
                case 'i':
                case 'I':
                    if (match(&s,"nf")) {
                        --s;
                        if (!match(&s,"inity"))
                            ++s;
                        word0(rv) = 0x7ff00000;
                        word1(rv) = 0;
                        goto ret;
                    }
                    break;
                case 'n':
                case 'N':
                    if (match(&s, "an")) {
                        word0(rv) = NAN_WORD0;
                        word1(rv) = NAN_WORD1;
#ifndef No_Hex_NaN
                        if (*s == '(') /*)*/
                            hexnan(&rv, &s);
#endif
                        goto ret;
                    }
            }
#endif /* INFNAN_CHECK */
ret0:
            s = s00;
            sign = 0;
        }
        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;
    dval(rv) = y;
    if (k > 9) {
#ifdef SET_INEXACT
        if (k > DBL_DIG)
            oldinexact = get_inexact();
#endif
        dval(rv) = tens[k - 9] * dval(rv) + z;
    }
    bd0 = 0;
    if (nd <= DBL_DIG && Flt_Rounds == 1) {
        if (!e)
            goto ret;
        if (e > 0) {
            if (e <= Ten_pmax) {
                /* rv = */ rounded_product(dval(rv), tens[e]);
                goto ret;
            }
            i = DBL_DIG - nd;
            if (e <= Ten_pmax + i) {
                /* A fancier test would sometimes let us do
                 * this for larger i values.
                 */
                e -= i;
                dval(rv) *= tens[i];
                /* rv = */ rounded_product(dval(rv), tens[e]);
                goto ret;
            }
        }
#ifndef Inaccurate_Divide
        else if (e >= -Ten_pmax) {
            /* rv = */ rounded_quotient(dval(rv), tens[-e]);
            goto ret;
        }
#endif
    }
    e1 += nd - k;

#ifdef SET_INEXACT
    inexact = 1;
    if (k <= DBL_DIG)
        oldinexact = get_inexact();
#endif
#ifdef Avoid_Underflow
    scale = 0;
#endif

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

    if (e1 > 0) {
        if ((i = e1 & 15))
            dval(rv) *= tens[i];
        if (e1 &= ~15) {
            if (e1 > DBL_MAX_10_EXP) {
ovfl:
#ifndef NO_ERRNO
                errno = ERANGE;
#endif
                /* Can't trust HUGE_VAL */
                word0(rv) = Exp_mask;
                word1(rv) = 0;
#ifdef SET_INEXACT
                /* set overflow bit */
                dval(rv0) = 1e300;
                dval(rv0) *= dval(rv0);
#endif
                if (bd0)
                    goto retfree;
                goto ret;
            }
            e1 >>= 4;
            for (j = 0; e1 > 1; j++, e1 >>= 1)
                if (e1 & 1)
                    dval(rv) *= bigtens[j];
        /* The last multiplication could overflow. */
            word0(rv) -= P * Exp_msk1;
            dval(rv) *= bigtens[j];
            if ((z = word0(rv) & Exp_mask) > Exp_msk1 * (DBL_MAX_EXP + Bias - P))
                goto ovfl;
            if (z > Exp_msk1 * (DBL_MAX_EXP + Bias - 1 - P)) {
                /* set to largest number */
                /* (Can't trust DBL_MAX) */
                word0(rv) = Big0;
                word1(rv) = Big1;
            } else
                word0(rv) += P * Exp_msk1;
        }
    } else if (e1 < 0) {
        e1 = -e1;
        if ((i = e1 & 15))
            dval(rv) /= tens[i];
        if (e1 >>= 4) {
            if (e1 >= 1 << n_bigtens)
                goto undfl;
#ifdef Avoid_Underflow
            if (e1 & Scale_Bit)
                scale = 2 * P;
            for (j = 0; e1 > 0; j++, e1 >>= 1)
                if (e1 & 1)
                    dval(rv) *= tinytens[j];
            if (scale && (j = (2 * P) + 1 - ((word0(rv) & Exp_mask) >> Exp_shift)) > 0) {
                /* scaled rv is denormal; zap j low bits */
                if (j >= 32) {
                    word1(rv) = 0;
                    if (j >= 53)
                       word0(rv) = (P + 2) * Exp_msk1;
                    else
                       word0(rv) &= 0xffffffff << j - 32;
                } else
                    word1(rv) &= 0xffffffff << j;
            }
#else
            for (j = 0; e1 > 1; j++, e1 >>= 1)
                if (e1 & 1)
                    dval(rv) *= tinytens[j];
            /* The last multiplication could underflow. */
            dval(rv0) = dval(rv);
            dval(rv) *= tinytens[j];
            if (!dval(rv)) {
                dval(rv) = 2. * dval(rv0);
                dval(rv) *= tinytens[j];
#endif
                if (!dval(rv)) {
undfl:
                    dval(rv) = 0.;
#ifndef NO_ERRNO
                    errno = ERANGE;
#endif
                    if (bd0)
                        goto retfree;
                    goto ret;
                }
#ifndef Avoid_Underflow
                word0(rv) = Tiny0;
                word1(rv) = Tiny1;
                /* The refinement below will clean
                 * this approximation up.
                 */
            }
#endif
        }
    }

    /* 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);

    for (;;) {
        bd = Balloc(bd0->k);
        Bcopy(bd, bd0);
        bb = d2b(dval(rv), &bbe, &bbbits);    /* rv = bb * 2^bbe */
        bs = i2b(1);

        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;
#ifdef Avoid_Underflow
        j = bbe - scale;
        i = j + bbbits - 1;    /* logb(rv) */
        if (i < Emin)    /* denormal */
            j += P - Emin;
        else
            j = P + 1 - bbbits;
#else /*Avoid_Underflow*/
#ifdef Sudden_Underflow
        j = P + 1 - bbbits;
#else /*Sudden_Underflow*/
        j = bbe;
        i = j + bbbits - 1;    /* logb(rv) */
        if (i < Emin)    /* denormal */
            j += P - Emin;
        else
            j = P + 1 - bbbits;
#endif /*Sudden_Underflow*/
#endif /*Avoid_Underflow*/
        bb2 += j;
        bd2 += j;
#ifdef Avoid_Underflow
        bd2 += scale;
#endif
        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);
            bb1 = mult(bs, bb);
            Bfree(bb);
            bb = bb1;
        }
        if (bb2 > 0)
            bb = lshift(bb, bb2);
        if (bd5 > 0)
            bd = pow5mult(bd, bd5);
        if (bd2 > 0)
            bd = lshift(bd, bd2);
        if (bs2 > 0)
            bs = lshift(bs, bs2);
        delta = diff(bb, bd);
        dsign = delta->sign;
        delta->sign = 0;
        i = cmp(delta, bs);

        if (i < 0) {
            /* Error is less than half an ulp -- check for