From 8c1629af42a10ff7e23bb40100a259bf334a9c60 Mon Sep 17 00:00:00 2001
From: Matthias Schiffer <mschiffer@universe-factory.net>
Date: Mon, 2 Feb 2015 01:41:17 +0100
Subject: Change region reader to a visitor pattern

Not keeping the whole region in memory reduces the needed space
to less than 5MB (from about 140).
---
 src/World/Region.cpp | 13 +++++++++----
 src/World/Region.hpp | 16 ++++++----------
 2 files changed, 15 insertions(+), 14 deletions(-)

(limited to 'src/World')

diff --git a/src/World/Region.cpp b/src/World/Region.cpp
index fec732c..4551d73 100644
--- a/src/World/Region.cpp
+++ b/src/World/Region.cpp
@@ -54,7 +54,7 @@ Region::ChunkMap Region::processHeader(const uint8_t header[4096]) {
 	return map;
 }
 
-Region::Region(const char *filename) {
+void Region::visitChunks(const char *filename, ChunkVisitor visitor) {
 	std::ifstream file;
 	file.exceptions(std::ios::failbit | std::ios::badbit);
 	file.open(filename, std::ios::in | std::ios::binary);
@@ -68,6 +68,8 @@ Region::Region(const char *filename) {
 		chunkMap = processHeader(header);
 	}
 
+	bool seen[SIZE][SIZE] = {};
+
 	size_t i = 1, c = 0;
 	while (!file.eof()) {
 		auto it = chunkMap.find(i);
@@ -80,16 +82,19 @@ Region::Region(const char *filename) {
 		size_t x, z, len;
 		std::tie(x, z, len) = it->second;
 
-		if (chunks[x][z])
+		if (seen[x][z])
 			throw std::invalid_argument("duplicate chunk");
 
+		seen[x][z] = true;
+		c++;
+
 		uint8_t buffer[len * 4096];
 		file.read((char *)buffer, len * 4096);
 
-		chunks[x][z].reset(new Chunk(Buffer(buffer, len * 4096)));
+		Chunk chunk(Buffer(buffer, len * 4096));
+		visitor(x, z, &chunk);
 
 		i += len;
-		c++;
 	}
 
 	if (c != chunkMap.size())
diff --git a/src/World/Region.hpp b/src/World/Region.hpp
index 0843724..d88dbe1 100644
--- a/src/World/Region.hpp
+++ b/src/World/Region.hpp
@@ -28,6 +28,7 @@
 
 #include "Chunk.hpp"
 
+#include <functional>
 #include <memory>
 #include <stdexcept>
 #include <tuple>
@@ -41,23 +42,18 @@ class Region {
 public:
 	static const size_t SIZE = 32;
 
+	typedef std::function<void (size_t, size_t, const Chunk *)> ChunkVisitor;
+
+	Region() = delete;
+
 private:
 	typedef std::tuple<size_t, size_t, size_t> ChunkDesc;
 	typedef std::unordered_map<size_t, ChunkDesc> ChunkMap;
 
-	std::unique_ptr<Chunk> chunks[SIZE][SIZE];
-
 	static ChunkMap processHeader(const uint8_t header[4096]);
 
 public:
-	Region(const char *filename);
-
-	const Chunk * operator()(size_t x, size_t z) {
-		if (x >= SIZE || z >= SIZE)
-			throw std::range_error("Region(): bad coordinates");
-
-		return chunks[x][z].get();
-	}
+	static void visitChunks(const char *filename, ChunkVisitor visitor);
 };
 
 }
-- 
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