Rewrite flood_water to use CoordStack and fix stack overflow, fixes #646

src/simulation/ElementDefs.h

@@ -34,7 +34,7 @@
 
 #define FLAG_STAGNANT	0x1
 #define FLAG_SKIPMOVE  0x2 // skip movement for one frame, only implemented for PHOT
-#define FLAG_WATEREQUAL 0x4 //if a liquid was already checked during equalization
+//#define FLAG_WATEREQUAL 0x4 //if a liquid was already checked during equalization
 #define FLAG_MOVABLE  0x8 // compatibility with old saves (moving SPNG), only applies to SPNG
 #define FLAG_PHOTDECO  0x8 // compatibility with old saves (decorated photons), only applies to PHOT. Having the same value as FLAG_MOVABLE is fine because they apply to different elements, and this saves space for future flags,
 

src/simulation/Simulation.cpp

@@ -866,63 +866,70 @@ int Simulation::FloodINST(int x, int y, int fullc, int cm)
 	return created_something;
 }
 
-int Simulation::flood_water(int x, int y, int i, int originaly, int check)
+bool Simulation::flood_water(int x, int y, int i)
 {
-	int x1 = 0,x2 = 0;
-	// go left as far as possible
-	x1 = x2 = x;
-	if (!pmap[y][x])
-		return 1;
+	int x1, x2, originalY = y;
+	int r = pmap[y][x];
+	if (!r)
+		return false;
 
-	while (x1>=CELL)
-	{
-		if ((elements[TYP(pmap[y][x1-1])].Falldown) != 2)
-		{
-			break;
-		}
-		x1--;
-	}
-	while (x2<XRES-CELL)
+	// Bitmap for checking where we've already looked
+	auto bitmapPtr = std::unique_ptr<char[]>(new char[XRES * YRES]);
+	char *bitmap = bitmapPtr.get();
+	std::fill(&bitmap[0], &bitmap[XRES * YRES], 0);
+
+	try
 	{
-		if ((elements[TYP(pmap[y][x2+1])].Falldown) != 2)
+		CoordStack cs;
+		cs.push(x, y);
+		do
 		{
-			break;
-		}
-		x2++;
-	}
+			cs.pop(x, y);
+			x1 = x2 = x;
+			while (x1 >= CELL)
+			{
+				if (elements[TYP(pmap[y][x1 - 1])].Falldown != 2 || bitmap[(y * XRES) + x1 - 1])
+					break;
+				x1--;
+			}
+			while (x2 < XRES-CELL)
+			{
+				if (elements[TYP(pmap[y][x2 + 1])].Falldown != 2 || bitmap[(y * XRES) + x1 - 1])
+					break;
+				x2++;
+			}
+			for (int x = x1; x <= x2; x++)
+			{
+				// Check above, maybe around other sides too?
+				if (((y - 1) > originalY) && !pmap[y - 1][x] && eval_move(parts[i].type, x, y - 1, nullptr))
+				{
+					int oldx = (int)(parts[i].x + 0.5f);
+					int oldy = (int)(parts[i].y + 0.5f);
+					pmap[y - 1][x] = pmap[oldy][oldx];
+					pmap[oldy][oldx] = 0;
+					parts[i].x = x;
+					parts[i].y = y - 1;
+					return true;
+				}
 
-	// fill span
-	for (x=x1; x<=x2; x++)
+				bitmap[(y * XRES) + x] = 1;
+			}
+			if (y >= CELL + 1)
+				for (int x = x1; x <= x2; x++)
+					if (elements[TYP(pmap[y - 1][x])].Falldown == 2 && !bitmap[((y - 1) * XRES) + x])
+						cs.push(x, y - 1);
+			if (y < YRES - CELL - 1)
+				for (int x = x1; x <= x2; x++)
+					if (elements[TYP(pmap[y + 1][x])].Falldown == 2 && !bitmap[((y + 1) * XRES) + x])
+						cs.push(x, y + 1);
+		} while (cs.getSize() > 0);
+	}
+	catch (std::exception &e)
 	{
-		if (check)
-			parts[ID(pmap[y][x])].flags &= ~FLAG_WATEREQUAL;//flag it as checked (different from the original particle's checked flag)
-		else
-			parts[ID(pmap[y][x])].flags |= FLAG_WATEREQUAL;
-		//check above, maybe around other sides too?
-		if ( ((y-1) > originaly) && !pmap[y-1][x] && eval_move(parts[i].type, x, y-1, NULL))
-		{
-			int oldx = (int)(parts[i].x + 0.5f);
-			int oldy = (int)(parts[i].y + 0.5f);
-			pmap[y-1][x] = pmap[oldy][oldx];
-			pmap[oldy][oldx] = 0;
-			parts[i].x = x;
-			parts[i].y = y-1;
-			return 0;
-		}
+		std::cerr << e.what() << std::endl;
+		return false;
 	}
-	// fill children
-
-	if (y>=CELL+1)
-		for (x=x1; x<=x2; x++)
-			if ((elements[TYP(pmap[y-1][x])].Falldown)==2 && (parts[ID(pmap[y-1][x])].flags & FLAG_WATEREQUAL) == check)
-				if (!flood_water(x, y-1, i, originaly, check))
-					return 0;
-	if (y<YRES-CELL-1)
-		for (x=x1; x<=x2; x++)
-			if ((elements[TYP(pmap[y+1][x])].Falldown)==2 && (parts[ID(pmap[y+1][x])].flags & FLAG_WATEREQUAL) == check)
-				if (!flood_water(x, y+1, i, originaly, check))
-					return 0;
-	return 1;
+	return false;
 }
 
 void Simulation::SetEdgeMode(int newEdgeMode)
@@ -4651,7 +4658,7 @@ void Simulation::UpdateParticles(int start, int end)
 				// Checking stagnant is cool, but then it doesn't update when you change it later.
 				if (water_equal_test && elements[t].Falldown == 2 && RNG::Ref().chance(1, 200))
 				{
-					if (!flood_water(x,y,i,y, parts[i].flags&FLAG_WATEREQUAL))
+					if (!flood_water(x, y, i))
 						goto movedone;
 				}
 				// liquids and powders

src/simulation/Simulation.h

@@ -142,7 +142,7 @@ class Simulation
 	void kill_part(int i);
 	bool FloodFillPmapCheck(int x, int y, int type);
 	int flood_prop(int x, int y, size_t propoffset, PropertyValue propvalue, StructProperty::PropertyType proptype);
-	int flood_water(int x, int y, int i, int originaly, int check);
+	bool flood_water(int x, int y, int i);
 	int FloodINST(int x, int y, int fullc, int cm);
 	void detach(int i);
 	bool part_change_type(int i, int x, int y, int t);