public static List <Island> DetectIslands(Map map)
{
int width = map.Width;
int height = map.Height;
int blockCount = width * height;
Block *matrix = map.GetBlockMatrix();
//
List <Island> islands = new List <Island>();
//allocate and initialize the search matrix
//so we can check which blocks we have already
//added/searched.
searchBlock *searchMatrix = (searchBlock *)Marshal.AllocHGlobal(
sizeof(searchBlock) * blockCount);
Block * matrixPtr = matrix;
searchBlock *ptr = searchMatrix;
searchBlock *ptrEnd = ptr + blockCount;
Block * mapPtr = matrix;
while (ptr != ptrEnd)
{
searchBlock *current = ptr++;
(*current).searched = false;
(*current).block = matrixPtr++;
}
//iterate through every block until we find every island
ptr = searchMatrix;
matrixPtr = matrix;
int currentIslandIndex = 0;
while (ptr != ptrEnd)
{
Block block = *matrixPtr++;
//searched before?
searchBlock *current = ptr++;
if ((*current).searched)
{
continue;
}
//land?
if (block.TypeID != Globals.TERRAIN_WATER)
{
//we hit an island
islandInfo info = floodSearch(
current,
currentIslandIndex++,
width,
searchMatrix,
ptrEnd);
//
Island i = new Island(
map,
info.blocks,
info.minX,
info.minY,
info.maxX - info.minX,
info.maxY - info.minY);
}
}
return(islands);
}
private static islandInfo floodSearch(searchBlock *block, int islandIndex, int rowWidth, searchBlock *start, searchBlock *end)
{
//create a queue to store pending blocks to
//be processed.
PtrQueue queue = new PtrQueue(10000);
queue.Push(block);
int count = 1;
//count how many blocks we found
int found = 0;
//used to detect the size and location
//of the island.
int minX = 0, minY = 0;
int maxX = 0, maxY = 0;
minX = minY = int.MaxValue;
//process every block
List <IntPtr> blocks = new List <IntPtr>();
while (count != 0)
{
searchBlock *ptr = (searchBlock *)queue.Pop();
count--;
//verify not out of bounds
if (ptr < start || ptr >= end)
{
continue;
}
searchBlock deref = *ptr;
//searched already?
if (deref.searched)
{
continue;
}
//mark as processed
(*ptr).searched = true;
//we hit the water?
Block b = (*deref.block);
if (b.TypeID == Globals.TERRAIN_WATER)
{
continue;
}
found++;
//add the block to the island
blocks.Add((IntPtr)deref.block);
//calculate x/y and do min/max to
//detect island size/location
int x = (int)((long)(ptr - start) % rowWidth);
int y = (int)((long)(ptr - start) / rowWidth);
if (x < minX)
{
minX = x;
}
if (y < minY)
{
minY = y;
}
if (x > maxX)
{
maxX = x;
}
if (y > maxY)
{
maxY = y;
}
#region reiterate for all 8 neighbors
/*top row*/
queue.Push(ptr - rowWidth);
queue.Push(ptr - rowWidth - 1);
queue.Push(ptr - rowWidth + 1);
/*bottom row*/
queue.Push(ptr + rowWidth);
queue.Push(ptr + rowWidth - 1);
queue.Push(ptr + rowWidth + 1);
/*left/right*/
queue.Push(ptr - 1);
queue.Push(ptr + 1);
count += 8;
#endregion
}
return(new islandInfo {
count = found,
minX = minX,
minY = minY,
maxX = maxX,
maxY = maxY,
blocks = blocks
});
}
