Source code
Revision control
Copy as Markdown
Other Tools
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
#include "prlong.h"
static PRInt64 ll_zero = PR_INT64(0x0000000000000000);
static PRInt64 ll_maxint = PR_INT64(0x7fffffffffffffff);
static PRInt64 ll_minint = PR_INT64(0x8000000000000000);
static PRUint64 ll_maxuint = PR_UINT64(0xffffffffffffffff);
PR_IMPLEMENT(PRInt64) LL_Zero(void) {
return ll_zero;
}
PR_IMPLEMENT(PRInt64) LL_MaxInt(void) {
return ll_maxint;
}
PR_IMPLEMENT(PRInt64) LL_MinInt(void) {
return ll_minint;
}
PR_IMPLEMENT(PRUint64) LL_MaxUint(void) {
return ll_maxuint;
}
#ifndef HAVE_LONG_LONG
/*
** Divide 64-bit a by 32-bit b, which must be normalized so its high bit is 1.
*/
static void norm_udivmod32(PRUint32 *qp, PRUint32 *rp, PRUint64 a, PRUint32 b)
{
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;
}
static PRUint32 CountLeadingZeros(PRUint32 a)
{
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;
}
PR_IMPLEMENT(void) ll_udivmod(PRUint64 *qp, PRUint64 *rp, PRUint64 a, PRUint64 b)
{
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;
}
}
#endif /* !HAVE_LONG_LONG */