Function sortCompare

src/sort.cpp:142–189

sortCompare() is used by qsort in sortCommand(). Given that qsort_r with * the additional parameter is not standard but a BSD-specific we have to * pass sorting parameters via the global 'server' structure */

 * the additional parameter is not standard but a BSD-specific we have to
 * pass sorting parameters via the global 'server' structure */
int sortCompare(const void *s1, const void *s2) {
    const redisSortObject *so1 = (redisSortObject*)s1, *so2 = (redisSortObject*)s2;
    int cmp;

    if (!g_pserver->sort_alpha) {
        /* Numeric sorting. Here it's trivial as we precomputed scores */
        if (so1->u.score > so2->u.score) {
            cmp = 1;
        } else if (so1->u.score < so2->u.score) {
            cmp = -1;
        } else {
            /* Objects have the same score, but we don't want the comparison
             * to be undefined, so we compare objects lexicographically.
             * This way the result of SORT is deterministic. */
            cmp = compareStringObjects(so1->obj,so2->obj);
        }
    } else {
        /* Alphanumeric sorting */
        if (g_pserver->sort_bypattern) {
            if (!so1->u.cmpobj || !so2->u.cmpobj) {
                /* At least one compare object is NULL */
                if (so1->u.cmpobj == so2->u.cmpobj)
                    cmp = 0;
                else if (so1->u.cmpobj == NULL)
                    cmp = -1;
                else
                    cmp = 1;
            } else {
                /* We have both the objects, compare them. */
                if (g_pserver->sort_store) {
                    cmp = compareStringObjects(so1->u.cmpobj,so2->u.cmpobj);
                } else {
                    /* Here we can use strcoll() directly as we are sure that
                     * the objects are decoded string objects. */
                    cmp = strcoll(szFromObj(so1->u.cmpobj),szFromObj(so2->u.cmpobj));
                }
            }
        } else {
            /* Compare elements directly. */
            if (g_pserver->sort_store) {
                cmp = compareStringObjects(so1->obj,so2->obj);
            } else {
                cmp = collateStringObjects(so1->obj,so2->obj);
            }
        }
    }
    return g_pserver->sort_desc ? -cmp : cmp;
}

/* The SORT command is the most complex command in Redis. Warning: this code
 * is optimized for speed and a bit less for readability */