find_nodes_in_area: Extend maximal count to U32_MAX (#5277)

Extend documentation, limit area volume
Remove u16 count limitation

* Prevent integer overflow, replace minp/maxp with pos1/pos2

doc/lua_api.txt

@@ -2465,12 +2465,13 @@ and `minetest.auth_reload` call the authetification handler.
     * `nodenames`: e.g. `{"ignore", "group:tree"}` or `"default:dirt"`
     * `search_center` is an optional boolean (default: `false`)
       If true `pos` is also checked for the nodes
-* `minetest.find_nodes_in_area(minp, maxp, nodenames)`: returns a list of positions
+* `minetest.find_nodes_in_area(pos1, pos2, nodenames)`: returns a list of positions
-    * returns as second value a table with the count of the individual nodes found
     * `nodenames`: e.g. `{"ignore", "group:tree"}` or `"default:dirt"`
-* `minetest.find_nodes_in_area_under_air(minp, maxp, nodenames)`: returns a list of positions
+    * First return value: Table with all node positions
-    * returned positions are nodes with a node air above
+    * Second return value: Table with the count of each node with the node name as index
+* `minetest.find_nodes_in_area_under_air(pos1, pos2, nodenames)`: returns a list of positions
     * `nodenames`: e.g. `{"ignore", "group:tree"}` or `"default:dirt"`
+    * Return value: Table with all node positions with a node air above
 * `minetest.get_perlin(noiseparams)`
 * `minetest.get_perlin(seeddiff, octaves, persistence, scale)`
     * Return world-specific perlin noise (`int(worldseed)+seeddiff`)

src/script/lua_api/l_env.cpp

@@ -651,11 +651,24 @@ int ModApiEnvMod::l_find_nodes_in_area(lua_State *L)
 	INodeDefManager *ndef = getServer(L)->ndef();
 	v3s16 minp = read_v3s16(L, 1);
 	v3s16 maxp = read_v3s16(L, 2);
+	sortBoxVerticies(minp, maxp);
+
+	v3s16 cube = maxp - minp + 1;
+
+	/* Limit for too large areas, assume default values
+	 * and give tolerances of 1 node on each side
+	 * (chunksize * MAP_BLOCKSIZE + 2)^3 = 551368
+	*/
+	if ((u64)cube.X * (u64)cube.Y * (u64)cube.Z > 551368) {
+		luaL_error(L, "find_nodes_in_area(): area volume"
+				" exceeds allowed value of 551368");
+		return 0;
+	}
+
 	std::set<content_t> filter;
 	if (lua_istable(L, 3)) {
-		int table = 3;
 		lua_pushnil(L);
-		while(lua_next(L, table) != 0) {
+		while (lua_next(L, 3) != 0) {
 			// key at index -2 and value at index -1
 			luaL_checktype(L, -1, LUA_TSTRING);
 			ndef->getIds(lua_tostring(L, -1), filter);
@@ -666,7 +679,7 @@ int ModApiEnvMod::l_find_nodes_in_area(lua_State *L)
 		ndef->getIds(lua_tostring(L, 3), filter);
 	}
 
-	std::map<content_t, u16> individual_count;
+	std::unordered_map<content_t, u32> individual_count;
 
 	lua_newtable(L);
 	u64 i = 0;
@@ -682,7 +695,7 @@ int ModApiEnvMod::l_find_nodes_in_area(lua_State *L)
 		}
 	}
 	lua_newtable(L);
-	for (std::set<content_t>::iterator it = filter.begin();
+	for (std::set<content_t>::const_iterator it = filter.begin();
 			it != filter.end(); ++it) {
 		lua_pushnumber(L, individual_count[*it]);
 		lua_setfield(L, -2, ndef->get(*it).name.c_str());
@@ -706,12 +719,25 @@ int ModApiEnvMod::l_find_nodes_in_area_under_air(lua_State *L)
 	INodeDefManager *ndef = getServer(L)->ndef();
 	v3s16 minp = read_v3s16(L, 1);
 	v3s16 maxp = read_v3s16(L, 2);
+	sortBoxVerticies(minp, maxp);
+
+	v3s16 cube = maxp - minp + 1;
+
+	/* Limit for too large areas, assume default values
+	 * and give tolerances of 1 node on each side
+	 * (chunksize * MAP_BLOCKSIZE + 2)^3 = 551368
+	*/
+	if ((u64)cube.X * (u64)cube.Y * (u64)cube.Z > 551368) {
+		luaL_error(L, "find_nodes_in_area_under_air(): area volume"
+				" exceeds allowed value of 551368");
+		return 0;
+	}
+
 	std::set<content_t> filter;
 
 	if (lua_istable(L, 3)) {
-		int table = 3;
 		lua_pushnil(L);
-		while(lua_next(L, table) != 0) {
+		while (lua_next(L, 3) != 0) {
 			// key at index -2 and value at index -1
 			luaL_checktype(L, -1, LUA_TSTRING);
 			ndef->getIds(lua_tostring(L, -1), filter);