Sheet Ore: Eliminate crash caused by PcgRandom range max < min

In the calculation of y_start, when 'column height max' was large it caused nmin.Y + max_height > nmax.Y - max_height Now, in this situation y_start is set to the midpoint between nmin.Y and nmax.Y Limit y0 and y1 to between nmin.Y and nmax.Y, otherwise index calculation, which has no checks for limits, places them at unwanted locations in the voxelmanip
minetest · Feb 23, 2016 · 8591713 · 8591713
1 parent 1474254
commit 8591713
Showing 1 changed file with 9 additions and 4 deletions.
diff --git a/src/mg_ore.cpp b/src/mg_ore.cpp
@@ -179,7 +179,12 @@ void OreSheet::generate(MMVManip *vm, int mapseed, u32 blockseed,
 	MapNode n_ore(c_ore, 0, ore_param2);
 
 	u16 max_height = column_height_max;
-	int y_start = pr.range(nmin.Y + max_height, nmax.Y - max_height);
+	int y_start_min = nmin.Y + max_height;
+	int y_start_max = nmax.Y - max_height;
+
+	int y_start = y_start_min < y_start_max ?
+		pr.range(y_start_min, y_start_max) :
+		(y_start_min + y_start_max) / 2;
 
 	if (!noise) {
 		int sx = nmax.X - nmin.X + 1;
@@ -204,10 +209,10 @@ void OreSheet::generate(MMVManip *vm, int mapseed, u32 blockseed,
 
 		u16 height = pr.range(column_height_min, column_height_max);
 		int ymidpoint = y_start + noiseval;
-		int y0 = ymidpoint - height * (1 - column_midpoint_factor);
-		int y1 = y0 + height;
+		int y0 = MYMAX(nmin.Y, ymidpoint - height * (1 - column_midpoint_factor));
+		int y1 = MYMIN(nmax.Y, y0 + height - 1);
 
-		for (int y = y0; y < y1; y++) {
+		for (int y = y0; y <= y1; y++) {
 			u32 i = vm->m_area.index(x, y, z);
 			if (!vm->m_area.contains(i))
 				continue;