Function getKeysUsingCommandTable

app/redis-6.2.6/src/db.c:1602–1636

The base case is to use the keys position as given in the command table * (firstkey, lastkey, step). */

/* The base case is to use the keys position as given in the command table
 * (firstkey, lastkey, step). */
int getKeysUsingCommandTable(struct redisCommand *cmd,robj **argv, int argc, getKeysResult *result) {
    int j, i = 0, last, *keys;
    UNUSED(argv);

    if (cmd->firstkey == 0) {
        result->numkeys = 0;
        return 0;
    }

    last = cmd->lastkey;
    if (last < 0) last = argc+last;

    int count = ((last - cmd->firstkey)+1);
    keys = getKeysPrepareResult(result, count);

    for (j = cmd->firstkey; j <= last; j += cmd->keystep) {
        if (j >= argc) {
            /* Modules commands, and standard commands with a not fixed number
             * of arguments (negative arity parameter) do not have dispatch
             * time arity checks, so we need to handle the case where the user
             * passed an invalid number of arguments here. In this case we
             * return no keys and expect the command implementation to report
             * an arity or syntax error. */
            if (cmd->flags & CMD_MODULE || cmd->arity < 0) {
                result->numkeys = 0;
                return 0;
            } else {
                serverPanic("Redis built-in command declared keys positions not matching the arity requirements.");
            }
        }
        keys[i++] = j;
    }
    result->numkeys = i;
    return i;
}

/* Return all the arguments that are keys in the command passed via argc / argv.
 *