static bool _fixup_duplicate_stairs(bool preserve_vault_stairs)

static bool _fixup_stone_stairs(bool preserve_vault_stairs)

    // This function ensures that there is no more than one of each up and down

    // This function ensures that there is exactly one each up and down

    // level connectivity).

    // level connectivity).  Fewer than three stone stairs will result in
    // random placement of new stairs.

        ASSERT(num_stairs <= 3);

        // If there are no stairs, it's either a branch entrance or exit.
        // If we somehow have ended up in a catastrophic "no stairs" state,
        // the level will not be validated, so we do not need to catch it here.
        if (num_stairs == 0)
            continue;

        if (num_stairs <= 1)

        // The top level doesn't connect to anything, so don't fix it.
        if (level_id::current() == level_id(BRANCH_MAIN_DUNGEON, 1) && i == 0)

        // At this point, up_stairs and down_stairs contain no more than
        // three stairs.  Ensure that they are unique.
        for (int s = 0; s < (num_stairs == 3 ? 4 : 1); s++)

        // Add extra stairs to get to exactly three.
        for (int s = num_stairs; s < 3; s++)
        {
            coord_def gc;
            do
            {
                gc.x = random2(GXM);
                gc.y = random2(GYM);
            }
            while (grd(gc) != DNGN_FLOOR);
            // base gets fixed up to be the right stone stair below...
            grd(gc) = base;
            stair_list[num_stairs++] = gc;
        }
        ASSERT(num_stairs == 3);
        // Ensure uniqueness of three stairs.
        for (int s = 0; s < 4; s++)

    if (!_fixup_duplicate_stairs(true))

    if (!_fixup_stone_stairs(true))

        _fixup_duplicate_stairs(false);

        _fixup_stone_stairs(false);