/**
* Lookup function for building road parts when building on slopes is disabled.
* @param slope The slope of the tile to examine.
* @param existing The existing road parts.
* @param start The part that should be build first.
* @param end The part that will be build second.
* @return 0 when the build parts do not connect, 1 when they do connect once
* they are build or 2 when building the first part automatically
* builds the second part.
*/
static int32 LookupWithoutBuildOnSlopes(::Slope slope, const Array *existing, int32 start, int32 end)
{
switch (slope) {
/* Flat slopes can always be build. */
case SLOPE_FLAT:
return 1;
/* Only 4 of the slopes can be build upon. Testing the existing bits is
* necessary because these bits can be something else when the settings
* in the game have been changed.
*/
case SLOPE_NE: case SLOPE_SW:
return (CheckAutoExpandedRoadBits(existing, start, end) && (start == 1 || end == 1)) ? (existing->size == 0 ? 2 : 1) : 0;
case SLOPE_SE: case SLOPE_NW:
return (CheckAutoExpandedRoadBits(existing, start, end) && (start != 1 && end != 1)) ? (existing->size == 0 ? 2 : 1) : 0;
/* Any other tile cannot be built on. */
default:
return 0;
}
}
/**
* Lookup function for building road parts when building on slopes is enabled.
* @param slope The slope of the tile to examine.
* @param existing The existing neighbours.
* @param start The part that should be build first.
* @param end The part that will be build second.
* @return 0 when the build parts do not connect, 1 when they do connect once
* they are build or 2 when building the first part automatically
* builds the second part.
*/
static int32 LookupWithBuildOnSlopes(::Slope slope, Array *existing, int32 start, int32 end)
{
if (::IsSteepSlope(slope)) {
switch (slope) {
/* On steep slopes one can only build straight roads that will be
* automatically expanded to a straight road. Just check that the existing
* road parts are in the same direction. */
case SLOPE_STEEP_S:
case SLOPE_STEEP_W:
case SLOPE_STEEP_N:
case SLOPE_STEEP_E:
return CheckAutoExpandedRoadBits(existing, start, end) ? (existing->size == 0 ? 2 : 1) : 0;
/* All other slopes are invalid slopes!. */
default:
return -1;
}
}
/* The slope is not steep. Furthermore lots of slopes are generally the
* same but are only rotated. So to reduce the amount of lookup work that
* needs to be done the data is made uniform. This means rotating the
* existing parts and updating the slope. */
static const ::Slope base_slopes[] = {
SLOPE_FLAT, SLOPE_W, SLOPE_W, SLOPE_SW,
SLOPE_W, SLOPE_EW, SLOPE_SW, SLOPE_WSE,
SLOPE_W, SLOPE_SW, SLOPE_EW, SLOPE_WSE,
SLOPE_SW, SLOPE_WSE, SLOPE_WSE};
static const byte base_rotates[] = {0, 0, 1, 0, 2, 0, 1, 0, 3, 3, 2, 3, 2, 2, 1};
if (slope >= (::Slope)lengthof(base_slopes)) {
/* This slope is an invalid slope, so ignore it. */
return -1;
}
byte base_rotate = base_rotates[slope];
slope = base_slopes[slope];
/* Some slopes don't need rotating, so return early when we know we do
* not need to rotate. */
switch (slope) {
case SLOPE_FLAT:
/* Flat slopes can always be build. */
return 1;
case SLOPE_EW:
case SLOPE_WSE:
/* A slope similar to a SLOPE_EW or SLOPE_WSE will always cause
* foundations which makes them accessible from all sides. */
return 1;
case SLOPE_W:
case SLOPE_SW:
/* A slope for which we need perform some calculations. */
break;
default:
/* An invalid slope. */
return -1;
}
/* Now perform the actual rotation. */
for (int j = 0; j < base_rotate; j++) {
for (int i = 0; i < existing->size; i++) {
existing->array[i] = RotateNeighbour(existing->array[i]);
}
start = RotateNeighbour(start);
end = RotateNeighbour(end);
}
/* Create roadbits out of the data for easier handling. */
RoadBits start_roadbits = NeighbourToRoadBits(start);
RoadBits new_roadbits = start_roadbits | NeighbourToRoadBits(end);
RoadBits existing_roadbits = ROAD_NONE;
for (int i = 0; i < existing->size; i++) {
existing_roadbits |= NeighbourToRoadBits(existing->array[i]);
}
switch (slope) {
case SLOPE_W:
/* A slope similar to a SLOPE_W. */
switch (new_roadbits) {
case ROAD_N:
case ROAD_E:
case ROAD_S:
/* Cannot build anything with a turn from the low side. */
return 0;
case ROAD_X:
case ROAD_Y:
/* A 'sloped' tile is going to be build. */
if ((existing_roadbits | new_roadbits) != new_roadbits) {
/* There is already a foundation on the tile, or at least
* another slope that is not compatible with the new one. */
return 0;
}
/* If the start is in the low part, it is automatically
* building the second part too. */
return ((start_roadbits & ROAD_E) && !(existing_roadbits & ROAD_W)) ? 2 : 1;
default:
/* Roadbits causing a foundation are going to be build.
* When the existing roadbits are slopes (the lower bits
* are used), this cannot be done. */
if ((existing_roadbits | new_roadbits) == new_roadbits) return 1;
return (existing_roadbits & ROAD_E) ? 0 : 1;
}
case SLOPE_SW:
/* A slope similar to a SLOPE_SW. */
switch (new_roadbits) {
case ROAD_N:
case ROAD_E:
/* Cannot build anything with a turn from the low side. */
return 0;
case ROAD_X:
/* A 'sloped' tile is going to be build. */
if ((existing_roadbits | new_roadbits) != new_roadbits) {
/* There is already a foundation on the tile, or at least
* another slope that is not compatible with the new one. */
return 0;
}
/* If the start is in the low part, it is automatically
* building the second part too. */
return ((start_roadbits & ROAD_NE) && !(existing_roadbits & ROAD_SW)) ? 2 : 1;
default:
/* Roadbits causing a foundation are going to be build.
* When the existing roadbits are slopes (the lower bits
* are used), this cannot be done. */
return (existing_roadbits & ROAD_NE) ? 0 : 1;
}
default:
NOT_REACHED();
}
}