Info: make tile existence map mor efficient for sparse worlds

Explicitly list the coordinates where tiles exist instead of including a
full array with the size of the bounding box.

src/Info.cpp

@@ -47,6 +47,9 @@ void Info::writeJSON(const char *filename) const {
 	std::fprintf(f, "\"mipmaps\":[");
 
 	for (size_t level = 0; level < regions.size(); level++) {
+		if (level != 0)
+			std::fprintf(f, ",");
+
 		int minX, maxX, minZ, maxZ;
 		std::tie(minX, maxX, minZ, maxZ) = getBounds(level);
 
@@ -57,30 +60,33 @@ void Info::writeJSON(const char *filename) const {
 		std::fprintf(f, "\"minZ\":%i,", minZ);
 		std::fprintf(f, "\"maxZ\":%i", maxZ);
 		std::fprintf(f, "},");
-		std::fprintf(f, "\"regions\":[");
+		std::fprintf(f, "\"regions\":{");
 
-		for (int z = minZ; z <= maxZ; z++) {
+		bool first_z = true;
-			std::fprintf(f, "[");
+		for (const auto &item : regions[level]) {
+			if (!first_z)
+				std::fprintf(f, ",");
+			first_z = false;
 
-			for (int x = minX; x <= maxX; x++) {
+			int z = item.first;
-				std::fprintf(f, "%s", regions[level].count(std::make_pair(x, z)) ? "true" : "false");
+			const std::set<int> &z_regions = item.second;
 
-				if (x < maxX)
+			std::fprintf(f, "\"%d\":[", z);
+
+			bool first_x = true;
+			for (int x : z_regions) {
+				if (!first_x)
 					std::fprintf(f, ",");
+				first_x = false;
+
+
+				std::fprintf(f, "%d", x);
 			}
 
-			if (z < maxZ)
+			std::fprintf(f, "]");
-				std::fprintf(f, "],");
-			else
-				std::fprintf(f, "]");
 		}
 
-		std::fprintf(f, "]");
+		std::fprintf(f, "}}");
-
-		if (level < regions.size() - 1)
-			std::fprintf(f, "},");
-		else
-			std::fprintf(f, "}");
 	}
 
 	std::fprintf(f, "],");

src/Info.hpp

@@ -29,6 +29,7 @@
 #include <climits>
 #include <cstddef>
 #include <cstdint>
+#include <map>
 #include <set>
 #include <tuple>
 #include <utility>
@@ -39,7 +40,7 @@ namespace MinedMap {
 
 class Info {
 private:
-	std::vector<std::set<std::pair<int, int>>> regions;
+	std::vector<std::map<int, std::set<int>>> regions;
 	std::vector<std::tuple<int, int, int, int>> bounds;
 
 	int32_t spawnX, spawnZ;
@@ -54,7 +55,12 @@ public:
 	}
 
 	void addRegion(int x, int z, size_t level) {
-		regions[level].insert(std::make_pair(x, z));
+		auto &level_r = regions[level];
+		auto z_regions = level_r.emplace(
+			std::piecewise_construct,
+			std::make_tuple(z),
+			std::make_tuple()).first;
+		z_regions->second.insert(x);
 
 		std::tuple<int, int, int, int> &b = bounds[level];
 

viewer/MinedMap.js

@@ -1,3 +1,22 @@
+// bsearch-based array element check
+function contains(array, elem) {
+	var min = 0, max = array.length, i, cur;
+
+	while (min < max) {
+		i = min + Math.floor((max-min)/2);
+		cur = array[i];
+
+		if (cur === elem)
+			return true;
+		else if (cur < elem)
+			min = i + 1;
+		else
+			max = i;
+	}
+
+	return false;
+}
+
 var MinedMapLayer = L.GridLayer.extend({
 	initialize: function (mipmaps, layer) {
 		this.mipmaps = mipmaps;
@@ -43,7 +62,7 @@ var MinedMapLayer = L.GridLayer.extend({
 
 		if (coords.x >= mipmap.info.minX && coords.x <= mipmap.info.maxX &&
 		    coords.y >= mipmap.info.minZ && coords.y <= mipmap.info.maxZ &&
-		    mipmap.regions[coords.y-mipmap.info.minZ][coords.x-mipmap.info.minX])
+		    contains(mipmap.regions[coords.y] || [], coords.x))
 			tile.src = 'data/'+this.layer+'/'+z+'/r.'+coords.x+'.'+coords.y+'.png';
 
 		if (z === 0)