漫话Redis源码之一百一十九

这个注释很清楚了：

/* Create a new user with the specified name, store it in the list
 * of users (the Users global radix tree), and returns a reference to
 * the structure representing the user.
 *
 * If the user with such name already exists NULL is returned. */

user *ACLCreateUser(const char *name, size_t namelen) {
    if (raxFind(Users,(unsigned char*)name,namelen) != raxNotFound) return NULL;
    user *u = zmalloc(sizeof(*u));
    u->name = sdsnewlen(name,namelen);
    u->flags = USER_FLAG_DISABLED | server.acl_pubsub_default;
    u->allowed_subcommands = NULL;
    u->passwords = listCreate();
    u->patterns = listCreate();
    u->channels = listCreate();
    listSetMatchMethod(u->passwords,ACLListMatchSds);
    listSetFreeMethod(u->passwords,ACLListFreeSds);
    listSetDupMethod(u->passwords,ACLListDupSds);
    listSetMatchMethod(u->patterns,ACLListMatchSds);
    listSetFreeMethod(u->patterns,ACLListFreeSds);
    listSetDupMethod(u->patterns,ACLListDupSds);
    listSetMatchMethod(u->channels,ACLListMatchSds);
    listSetFreeMethod(u->channels,ACLListFreeSds);
    listSetDupMethod(u->channels,ACLListDupSds);
    memset(u->allowed_commands,0,sizeof(u->allowed_commands));
    raxInsert(Users,(unsigned char*)name,namelen,u,NULL);
    return u;
}
 
/* This function should be called when we need an unlinked "fake" user
 * we can use in order to validate ACL rules or for other similar reasons.
 * The user will not get linked to the Users radix tree. The returned
 * user should be released with ACLFreeUser() as usually. */
user *ACLCreateUnlinkedUser(void) {
    char username[64];
    for (int j = 0; ; j++) {
        snprintf(username,sizeof(username),"__fakeuser:%d__",j);
        user *fakeuser = ACLCreateUser(username,strlen(username));
        if (fakeuser == NULL) continue;
        int retval = raxRemove(Users,(unsigned char*) username,
                               strlen(username),NULL);
        serverAssert(retval != 0);
        return fakeuser;
    }
}