Function getKeysPrepareResult

app/redis-6.2.6/src/db.c:1575–1598

Prepare the getKeysResult struct to hold numkeys, either by using the * pre-allocated keysbuf or by allocating a new array on the heap. * * This function must be called at least once before starting to populate * the result, and can be called repeatedly to enlarge the result array. */

 * the result, and can be called repeatedly to enlarge the result array.
 */
int *getKeysPrepareResult(getKeysResult *result, int numkeys) {
    /* GETKEYS_RESULT_INIT initializes keys to NULL, point it to the pre-allocated stack
     * buffer here. */
    if (!result->keys) {
        serverAssert(!result->numkeys);
        result->keys = result->keysbuf;
    }

    /* Resize if necessary */
    if (numkeys > result->size) {
        if (result->keys != result->keysbuf) {
            /* We're not using a static buffer, just (re)alloc */
            result->keys = zrealloc(result->keys, numkeys * sizeof(int));
        } else {
            /* We are using a static buffer, copy its contents */
            result->keys = zmalloc(numkeys * sizeof(int));
            if (result->numkeys)
                memcpy(result->keys, result->keysbuf, result->numkeys * sizeof(int));
        }
        result->size = numkeys;
    }

    return result->keys;
}

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