Back to index

lightning-sunbird  0.9+nobinonly
Functions | Variables
jslong.c File Reference
#include "jsstddef.h"
#include "jstypes.h"
#include "jslong.h"

Go to the source code of this file.

Functions

 JS_PUBLIC_API (JSInt64)
static void norm_udivmod32 (JSUint32 *qp, JSUint32 *rp, JSUint64 a, JSUint32 b)
static JSUint32 CountLeadingZeros (JSUint32 a)
 JS_PUBLIC_API (void)

Variables

static JSInt64 ll_zero = JSLL_INIT( 0x00000000,0x00000000 )
static JSInt64 ll_maxint = JSLL_INIT( 0x7fffffff, 0xffffffff )
static JSInt64 ll_minint = JSLL_INIT( 0x80000000, 0x00000000 )

Function Documentation

static JSUint32 CountLeadingZeros ( JSUint32  a) [static]

Definition at line 98 of file jslong.c.

{
    JSUint32 t;
    JSUint32 r = 32;

    if ((t = a >> 16) != 0)
        r -= 16, a = t;
    if ((t = a >> 8) != 0)
        r -= 8, a = t;
    if ((t = a >> 4) != 0)
        r -= 4, a = t;
    if ((t = a >> 2) != 0)
        r -= 2, a = t;
    if ((t = a >> 1) != 0)
        r -= 1, a = t;
    if (a & 1)
        r--;
    return r;
}

Here is the caller graph for this function:

Definition at line 55 of file jslong.c.

{ return ll_zero; }

Definition at line 118 of file jslong.c.

{
    JSUint32 n0, n1, n2;
    JSUint32 q0, q1;
    JSUint32 rsh, lsh;

    n0 = a.lo;
    n1 = a.hi;

    if (b.hi == 0) {
        if (b.lo > n1) {
            /* (0 q0) = (n1 n0) / (0 D0) */

            lsh = CountLeadingZeros(b.lo);

            if (lsh) {
                /*
                 * Normalize, i.e. make the most significant bit of the
                 * denominator be set.
                 */
                b.lo = b.lo << lsh;
                n1 = (n1 << lsh) | (n0 >> (32 - lsh));
                n0 = n0 << lsh;
            }

            a.lo = n0, a.hi = n1;
            norm_udivmod32(&q0, &n0, a, b.lo);
            q1 = 0;

            /* remainder is in n0 >> lsh */
        } else {
            /* (q1 q0) = (n1 n0) / (0 d0) */

            if (b.lo == 0)              /* user wants to divide by zero! */
                b.lo = 1 / b.lo;        /* so go ahead and crash */

            lsh = CountLeadingZeros(b.lo);

            if (lsh == 0) {
                /*
                 * From (n1 >= b.lo)
                 *   && (the most significant bit of b.lo is set),
                 * conclude that
                 *      (the most significant bit of n1 is set)
                 *   && (the leading quotient digit q1 = 1).
                 *
                 * This special case is necessary, not an optimization
                 * (Shifts counts of 32 are undefined).
                 */
                n1 -= b.lo;
                q1 = 1;
            } else {
                /*
                 * Normalize.
                 */
                rsh = 32 - lsh;

                b.lo = b.lo << lsh;
                n2 = n1 >> rsh;
                n1 = (n1 << lsh) | (n0 >> rsh);
                n0 = n0 << lsh;

                a.lo = n1, a.hi = n2;
                norm_udivmod32(&q1, &n1, a, b.lo);
            }

            /* n1 != b.lo... */

            a.lo = n0, a.hi = n1;
            norm_udivmod32(&q0, &n0, a, b.lo);

            /* remainder in n0 >> lsh */
        }

        if (rp) {
            rp->lo = n0 >> lsh;
            rp->hi = 0;
        }
    } else {
        if (b.hi > n1) {
            /* (0 0) = (n1 n0) / (D1 d0) */

            q0 = 0;
            q1 = 0;

            /* remainder in (n1 n0) */
            if (rp) {
                rp->lo = n0;
                rp->hi = n1;
            }
        } else {
            /* (0 q0) = (n1 n0) / (d1 d0) */

            lsh = CountLeadingZeros(b.hi);
            if (lsh == 0) {
                /*
                 * From (n1 >= b.hi)
                 *   && (the most significant bit of b.hi is set),
                 * conclude that
                 *      (the most significant bit of n1 is set)
                 *   && (the quotient digit q0 = 0 or 1).
                 *
                 * This special case is necessary, not an optimization.
                 */

                /*
                 * The condition on the next line takes advantage of that
                 * n1 >= b.hi (true due to control flow).
                 */
                if (n1 > b.hi || n0 >= b.lo) {
                    q0 = 1;
                    a.lo = n0, a.hi = n1;
                    JSLL_SUB(a, a, b);
                } else {
                    q0 = 0;
                }
                q1 = 0;

                if (rp) {
                    rp->lo = n0;
                    rp->hi = n1;
                }
            } else {
                JSInt64 m;

                /*
                 * Normalize.
                 */
                rsh = 32 - lsh;

                b.hi = (b.hi << lsh) | (b.lo >> rsh);
                b.lo = b.lo << lsh;
                n2 = n1 >> rsh;
                n1 = (n1 << lsh) | (n0 >> rsh);
                n0 = n0 << lsh;

                a.lo = n1, a.hi = n2;
                norm_udivmod32(&q0, &n1, a, b.hi);
                JSLL_MUL32(m, q0, b.lo);

                if ((m.hi > n1) || ((m.hi == n1) && (m.lo > n0))) {
                    q0--;
                    JSLL_SUB(m, m, b);
                }

                q1 = 0;

                /* Remainder is ((n1 n0) - (m1 m0)) >> lsh */
                if (rp) {
                    a.lo = n0, a.hi = n1;
                    JSLL_SUB(a, a, m);
                    rp->lo = (a.hi << rsh) | (a.lo >> lsh);
                    rp->hi = a.hi >> lsh;
                }
            }
        }
    }

    if (qp) {
        qp->lo = q0;
        qp->hi = q1;
    }
}
static void norm_udivmod32 ( JSUint32 *  qp,
JSUint32 *  rp,
JSUint64  a,
JSUint32  b 
) [static]

Definition at line 64 of file jslong.c.

{
    JSUint32 d1, d0, q1, q0;
    JSUint32 r1, r0, m;

    d1 = jshi16(b);
    d0 = jslo16(b);
    r1 = a.hi % d1;
    q1 = a.hi / d1;
    m = q1 * d0;
    r1 = (r1 << 16) | jshi16(a.lo);
    if (r1 < m) {
        q1--, r1 += b;
        if (r1 >= b     /* i.e., we didn't get a carry when adding to r1 */
            && r1 < m) {
            q1--, r1 += b;
        }
    }
    r1 -= m;
    r0 = r1 % d1;
    q0 = r1 / d1;
    m = q0 * d0;
    r0 = (r0 << 16) | jslo16(a.lo);
    if (r0 < m) {
        q0--, r0 += b;
        if (r0 >= b
            && r0 < m) {
            q0--, r0 += b;
        }
    }
    *qp = (q1 << 16) | q0;
    *rp = r0 - m;
}

Here is the call graph for this function:

Here is the caller graph for this function:


Variable Documentation

JSInt64 ll_maxint = JSLL_INIT( 0x7fffffff, 0xffffffff ) [static]

Definition at line 44 of file jslong.c.

JSInt64 ll_minint = JSLL_INIT( 0x80000000, 0x00000000 ) [static]

Definition at line 45 of file jslong.c.

JSInt64 ll_zero = JSLL_INIT( 0x00000000,0x00000000 ) [static]

Definition at line 43 of file jslong.c.