jsdtoa.c

java script test programing source code

    ULong borrow, carry, y, ys;
    ULong si, z, zs;
#endif

    n = S->wds;
    JS_ASSERT(b->wds <= n);
    if (b->wds < n)
        return 0;
    sx = S->x;
    sxe = sx + --n;
    bx = b->x;
    bxe = bx + n;
    JS_ASSERT(*sxe <= 0x7FFFFFFF);
    q = *bxe / (*sxe + 1);  /* ensure q <= true quotient */
    JS_ASSERT(q < 36);
    if (q) {
        borrow = 0;
        carry = 0;
        do {
#ifdef ULLong
            ys = *sx++ * (ULLong)q + carry;
            carry = ys >> 32;
            y = *bx - (ys & 0xffffffffUL) - borrow;
            borrow = y >> 32 & 1UL;
            *bx++ = (ULong)(y & 0xffffffffUL);
#else
            si = *sx++;
            ys = (si & 0xffff) * q + carry;
            zs = (si >> 16) * q + (ys >> 16);
            carry = zs >> 16;
            y = (*bx & 0xffff) - (ys & 0xffff) - borrow;
            borrow = (y & 0x10000) >> 16;
            z = (*bx >> 16) - (zs & 0xffff) - borrow;
            borrow = (z & 0x10000) >> 16;
            Storeinc(bx, z, y);
#endif
        }
        while(sx <= sxe);
        if (!*bxe) {
            bx = b->x;
            while(--bxe > bx && !*bxe)
                --n;
            b->wds = n;
        }
    }
    if (cmp(b, S) >= 0) {
        q++;
        borrow = 0;
        carry = 0;
        bx = b->x;
        sx = S->x;
        do {
#ifdef ULLong
            ys = *sx++ + carry;
            carry = ys >> 32;
            y = *bx - (ys & 0xffffffffUL) - borrow;
            borrow = y >> 32 & 1UL;
            *bx++ = (ULong)(y & 0xffffffffUL);
#else
            si = *sx++;
            ys = (si & 0xffff) + carry;
            zs = (si >> 16) + (ys >> 16);
            carry = zs >> 16;
            y = (*bx & 0xffff) - (ys & 0xffff) - borrow;
            borrow = (y & 0x10000) >> 16;
            z = (*bx >> 16) - (zs & 0xffff) - borrow;
            borrow = (z & 0x10000) >> 16;
            Storeinc(bx, z, y);
#endif
        } while(sx <= sxe);
        bx = b->x;
        bxe = bx + n;
        if (!*bxe) {
            while(--bxe > bx && !*bxe)
                --n;
            b->wds = n;
        }
    }
    return (int32)q;
}

/* 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. 92-101].
 *
 * 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) 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 assumption 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 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
 *     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.
 */

/* Always emits at least one digit. */
/* If biasUp is set, then rounding in modes 2 and 3 will round away from zero
 * when the number is exactly halfway between two representable values.  For example,
 * rounding 2.5 to zero digits after the decimal point will return 3 and not 2.
 * 2.49 will still round to 2, and 2.51 will still round to 3. */
/* bufsize should be at least 20 for modes 0 and 1.  For the other modes,
 * bufsize should be two greater than the maximum number of output characters expected. */
static JSBool
js_dtoa(double d, int mode, JSBool biasUp, int ndigits,
    int *decpt, int *sign, char **rve, char *buf, size_t bufsize)
{
    /*  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.
        4-9 should give the same return values as 2-3, i.e.,
        4 <= mode <= 9 ==> same return as mode
        2 + (mode & 1).  These modes are mainly for
        debugging; often they run slower but sometimes
        faster than modes 2-3.
        4,5,8,9 ==> left-to-right digit generation.
        6-9 ==> 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.
    */

    int32 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;
#ifndef Sudden_Underflow
    int32 denorm;
    ULong x;
#endif
    Bigint *b, *b1, *delta, *mlo, *mhi, *S;
    double d2, ds, eps;
    char *s;

    if (word0(d) & Sign_bit) {
        /* set sign for everything, including 0's and NaNs */
        *sign = 1;
        set_word0(d, word0(d) & ~Sign_bit);  /* clear sign bit */
    }
    else
        *sign = 0;

    if ((word0(d) & Exp_mask) == Exp_mask) {
        /* Infinity or NaN */
        *decpt = 9999;
        s = !word1(d) && !(word0(d) & Frac_mask) ? "Infinity" : "NaN";
        if ((s[0] == 'I' && bufsize < 9) || (s[0] == 'N' && bufsize < 4)) {
            JS_ASSERT(JS_FALSE);
/*          JS_SetError(JS_BUFFER_OVERFLOW_ERROR, 0); */
            return JS_FALSE;
        }
        strcpy(buf, s);
        if (rve) {
            *rve = buf[3] ? buf + 8 : buf + 3;
            JS_ASSERT(**rve == '\0');
        }
        return JS_TRUE;
    }

    b = NULL;                           /* initialize for abort protection */
    S = NULL;
    mlo = mhi = NULL;

    if (!d) {
      no_digits:
        *decpt = 1;
        if (bufsize < 2) {
            JS_ASSERT(JS_FALSE);
/*          JS_SetError(JS_BUFFER_OVERFLOW_ERROR, 0); */
            return JS_FALSE;
        }
        buf[0] = '0'; buf[1] = '\0';  /* copy "0" to buffer */
        if (rve)
            *rve = buf + 1;
        /* We might have jumped to "no_digits" from below, so we need
         * to be sure to free the potentially allocated Bigints to avoid
         * memory leaks. */
        Bfree(b);
        Bfree(S);
        if (mlo != mhi)
            Bfree(mlo);
        Bfree(mhi);
        return JS_TRUE;
    }

    b = d2b(d, &be, &bbits);
    if (!b)
        goto nomem;
#ifdef Sudden_Underflow
    i = (int32)(word0(d) >> Exp_shift1 & (Exp_mask>>Exp_shift1));
#else
    if ((i = (int32)(word0(d) >> Exp_shift1 & (Exp_mask>>Exp_shift1))) != 0) {
#endif
        d2 = d;
        set_word0(d2, word0(d2) & Frac_mask1);
        set_word0(d2, 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 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;
#ifndef Sudden_Underflow
        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);
        d2 = x;
        set_word0(d2, word0(d2) - 31*Exp_msk1); /* adjust exponent */
        i -= (Bias + (P-1) - 1) + 1;
        denorm = 1;
    }
#endif
    /* At this point d = f*2^i, where 1 <= f < 2.  d2 is an approximation of f. */
    ds = (d2-1.5)*0.289529654602168 + 0.1760912590558 + i*0.301029995663981;
    k = (int32)ds;
    if (ds < 0. && ds != k)
        k--;    /* want k = floor(ds) */
    k_check = 1;
    if (k >= 0 && k <= Ten_pmax) {
        if (d < tens[k])
            k--;
        k_check = 0;
    }
    /* At this point floor(log10(d)) <= k <= floor(log10(d))+1.
       If k_check is zero, we're guaranteed that k = floor(log10(d)). */
    j = bbits - i - 1;
    /* At this point d = b/2^j, where b is an odd integer. */
    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;
    }
    /* At this point d/10^k = (b * 2^b2 * 5^b5) / (2^s2 * 5^s5), where b is an odd integer,
       b2 >= 0, b5 >= 0, s2 >= 0, and s5 >= 0. */
    if (mode < 0 || mode > 9)
        mode = 0;
    try_quick = 1;
    if (mode > 5) {
        mode -= 4;
        try_quick = 0;
    }
    leftright = 1;
    ilim = ilim1 = 0;
    switch(mode) {
    case 0:
    case 1:
        ilim = ilim1 = -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;
    }
    /* ilim is the maximum number of significant digits we want, based on k and ndigits. */
    /* ilim1 is the maximum number of significant digits we want, based on k and ndigits,
       when it turns out that k was computed too high by one. */

    /* Ensure space for at least i+1 characters, including trailing null. */
    if (bufsize <= (size_t)i) {
        Bfree(b);
        JS_ASSERT(JS_FALSE);
        return JS_FALSE;
    }
    s = buf;

    if (ilim >= 0 && ilim <= Quick_max && try_quick) {

        /* Try to get by with floating-point arithmetic. */

        i = 0;
        d2 = d;
        k0 = k;
        ilim0 = ilim;
        ieps = 2; /* conservative */
        /* Divide d by 10^k, keeping track of the roundoff error and avoiding overflows. */
        if (k > 0) {
            ds = tens[k&0xf];
            j = k >> 4;
            if (j & Bletch) {
                /* prevent overflows */
                j &= Bletch - 1;
                d /= bigtens[n_bigtens-1];
                ieps++;
            }
            for(; j; j >>= 1, i++)
                if (j & 1) {
                    ieps++;
                    ds *= bigtens[i];
                }
            d /= ds;
        }
        else if ((j1 = -k) != 0) {
            d *= tens[j1 & 0xf];
            for(j = j1 >> 4; j; j >>= 1, i++)
                if (j & 1) {
                    ieps++;
                    d *= bigtens[i];
                }
        }
        /* Check that k was computed correctly. */
        if (k_check && d < 1. && ilim > 0) {
            if (ilim1 <= 0)
                goto fast_failed;
            ilim = ilim1;
            k--;
            d *= 10.;
            ieps++;
        }
        /* eps bounds the cumulative error. */
        eps = ieps*d + 7.;
        set_word0(eps, word0(eps) - (P-1)*Exp_msk1);
        if (ilim == 0) {
            S = mhi = 0;
            d -= 5.;
            if (d > eps)
                goto one_digit;
            if (d < -eps)
                goto no_digits;
            goto fast_failed;
        }
#ifndef No_leftright
        if (leftright) {
            /* Use Steele & White method of only
             * generating digits needed.
             */
            eps = 0.5/tens[ilim-1] - eps;
            for(i = 0;;) {
                L = (Long)d;
                d -= L;
                *s++ = '0' + (char)L;
                if (d < eps)
                    goto ret1;
                if (1. - d < eps)
                    goto bump_up;
                if (++i >= ilim)
                    break;
                eps *= 10.;
                d *= 10.;
            }
        }
        else {
#endif
            /* Generate ilim digits, then fix them up. */
            eps *= tens[ilim-1];
            for(i = 1;; i++, d *= 10.) {
                L = (Long)d;
                d -= L;
                *s++ = '0' + (char)L;
                if (i == ilim) {
                    if (d > 0.5 + eps)
                        goto bump_up;
                    else if (d < 0.5 - eps) {
                        while(*--s == '0') ;
                        s++;
                        goto ret1;
                    }
                    break;
                }
            }
#ifndef No_leftright
        }
#endif
    fast_failed:
        s = buf;
        d = d2;
        k = k0;
        ilim = ilim0;
    }

    /* Do we have a "small" integer? */

    if (be >= 0 && k <= Int_max) {
        /* Yes. */
        ds = tens[k];
        if (ndigits < 0 && ilim <= 0) {
            S = mhi = 0;
            if (ilim < 0 || d < 5*ds || (!biasUp && d == 5*ds))
                goto no_digits;
            goto one_digit;
        }

        /* Use true number of digits to limit looping. */
        for(i = 1; i<=k+1; i++) {
            L = (Long) (d / ds);
            d -= L*ds;
#ifdef Check_FLT_ROUNDS
            /* If FLT_ROUNDS == 2, L will usually be high by 1 */
            if (d < 0) {