DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Mercurial (a4c6303b2402)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254
/* -*- 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
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#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 */