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lightning-sunbird  0.9+nobinonly
Functions | Variables
prlong.c File Reference
#include "primpl.h"

Go to the source code of this file.

Functions

 PR_IMPLEMENT (PRInt64)
static void norm_udivmod32 (PRUint32 *qp, PRUint32 *rp, PRUint64 a, PRUint32 b)
static PRUint32 CountLeadingZeros (PRUint32 a)
 PR_IMPLEMENT (void)

Variables

static PRInt64 ll_zero = LL_INIT( 0x00000000,0x00000000 )
static PRInt64 ll_maxint = LL_INIT( 0x7fffffff, 0xffffffff )
static PRInt64 ll_minint = LL_INIT( 0x80000000, 0x00000000 )
static PRUint64 ll_maxuint = LL_INIT( 0xffffffff, 0xffffffff )

Function Documentation

static PRUint32 CountLeadingZeros ( PRUint32  a) [static]

Definition at line 99 of file prlong.c.

{
    PRUint32 t;
    PRUint32 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;
}

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static void norm_udivmod32 ( PRUint32 qp,
PRUint32 rp,
PRUint64  a,
PRUint32  b 
) [static]

Definition at line 65 of file prlong.c.

{
    PRUint32 d1, d0, q1, q0;
    PRUint32 r1, r0, m;

    d1 = _hi16(b);
    d0 = _lo16(b);
    r1 = a.hi % d1;
    q1 = a.hi / d1;
    m = q1 * d0;
    r1 = (r1 << 16) | _hi16(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) | _lo16(a.lo);
    if (r0 < m) {
        q0--, r0 += b;
        if (r0 >= b
           && r0 < m) {
           q0--, r0 += b;
       }
    }
    *qp = (q1 << 16) | q0;
    *rp = r0 - m;
}

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Definition at line 55 of file prlong.c.

{ return ll_zero; }

Definition at line 119 of file prlong.c.

{
    PRUint32 n0, n1, n2;
    PRUint32 q0, q1;
    PRUint32 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;
                  LL_SUB(a, a, b);
              } else {
                  q0 = 0;
              }
              q1 = 0;

              if (rp) {
                  rp->lo = n0;
                  rp->hi = n1;
              }
           } else {
              PRInt64 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);
              LL_MUL32(m, q0, b.lo);

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

              q1 = 0;

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

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Variable Documentation

PRInt64 ll_maxint = LL_INIT( 0x7fffffff, 0xffffffff ) [static]

Definition at line 41 of file prlong.c.

PRUint64 ll_maxuint = LL_INIT( 0xffffffff, 0xffffffff ) [static]

Definition at line 43 of file prlong.c.

PRInt64 ll_minint = LL_INIT( 0x80000000, 0x00000000 ) [static]

Definition at line 42 of file prlong.c.

PRInt64 ll_zero = LL_INIT( 0x00000000,0x00000000 ) [static]

Definition at line 40 of file prlong.c.