Compute top non-air layer

This doesn't yet ignore non-opaque blocks.

src/MinedMap.cpp

@@ -42,14 +42,7 @@ int main(int argc, char *argv[]) {
 	World::Region region(argv[1]);
 
 	const World::Chunk &chunk = *region(0, 0);
-
-	for (auto &entry : chunk.getSections()) {
-		std::cout << entry->getType() << ":" << std::endl;
-
-		for (auto &entry2 : *entry) {
-			std::cout << entry2.first << " " << entry2.second->getType() << std::endl;
-		}
-	}
+	World::Chunk::Blocks layer = chunk.getTopLayer();
 
 	return 0;
 }

src/World/Block.hpp

@@ -0,0 +1,41 @@
+/*
+  Copyright (c) 2015, Matthias Schiffer <mschiffer@universe-factory.net>
+  All rights reserved.
+
+  Redistribution and use in source and binary forms, with or without
+  modification, are permitted provided that the following conditions are met:
+
+    1. Redistributions of source code must retain the above copyright notice,
+       this list of conditions and the following disclaimer.
+    2. Redistributions in binary form must reproduce the above copyright notice,
+       this list of conditions and the following disclaimer in the documentation
+       and/or other materials provided with the distribution.
+
+  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+  DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+  OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+
+#pragma once
+
+#include <stdint.h>
+
+
+namespace MinedMap {
+namespace World {
+
+struct Block {
+	uint8_t id;
+	uint8_t data;
+};
+
+}
+}

src/World/Chunk.cpp

@@ -39,6 +39,20 @@
 namespace MinedMap {
 namespace World {
 
+Chunk::Chunk(Buffer buffer) {
+	size_t size = buffer.get32();
+
+	Buffer buffer2(buffer.get(size), size);
+
+	uint8_t format = buffer2.get8();
+	if (format != 2)
+		throw std::invalid_argument("unknown chunk format");
+
+	inflateChunk(buffer2);
+	parseChunk();
+	analyzeChunk();
+}
+
 void Chunk::inflateChunk(Buffer buffer) {
 	size_t outlen = 0;
 	uint8_t *output = nullptr;
@@ -97,11 +111,11 @@ void Chunk::analyzeChunk() {
 	}
 }
 
-uint8_t Chunk::getBlockAt(const std::shared_ptr<const NBT::CompoundTag> &section, size_t x, size_t y, size_t z) {
+uint8_t Chunk::getBlockAt(const std::shared_ptr<const NBT::CompoundTag> &section, size_t x, size_t y, size_t z) const {
 	return (*section->get<NBT::ByteArrayTag>("Blocks"))[getIndex(x, y, z)];
 }
 
-uint8_t Chunk::getDataAt(const std::shared_ptr<const NBT::CompoundTag> &section, size_t x, size_t y, size_t z) {
+uint8_t Chunk::getDataAt(const std::shared_ptr<const NBT::CompoundTag> &section, size_t x, size_t y, size_t z) const {
 	size_t i = getIndex(x, y, z);
 	uint8_t v = (*section->get<NBT::ByteArrayTag>("Data"))[i / 2];
 
@@ -111,18 +125,37 @@ uint8_t Chunk::getDataAt(const std::shared_ptr<const NBT::CompoundTag> &section,
 		return (v & 0xf);
 }
 
-Chunk::Chunk(Buffer buffer) {
-	size_t size = buffer.get32();
+Chunk::Blocks Chunk::getTopLayer() const {
+	size_t done = 0;
+	Blocks blocks = {};
 
-	Buffer buffer2(buffer.get(size), size);
+	for (auto it = sections->rbegin(); it != sections->rend(); ++it) {
+		if (done == SIZE*SIZE)
+			break;
 
-	uint8_t format = buffer2.get8();
-	if (format != 2)
-		throw std::invalid_argument("unknown chunk format");
+		for (ssize_t y = SIZE-1; y >= 0; y--) {
+			if (done == SIZE*SIZE)
+				break;
 
-	inflateChunk(buffer2);
-	parseChunk();
-	analyzeChunk();
+			for (size_t x = 0; x < SIZE; x++) {
+				for (size_t z = 0; z < SIZE; z++) {
+					if (blocks.blocks[x][z].id)
+						continue;
+
+					uint8_t block = getBlockAt(*it, x, y, z);
+					if (block) {
+						blocks.blocks[x][z].id = block;
+						blocks.blocks[x][z].data = getDataAt(*it, x, y, z);
+						done++;
+					}
+				}
+			}
+		}
+	}
+
+	std::cerr << "Done: " << done << std::endl;
+
+	return blocks;
 }
 
 }

src/World/Chunk.hpp

@@ -27,6 +27,7 @@
 #pragma once
 
 
+#include "Block.hpp"
 #include "../Buffer.hpp"
 #include "../UniqueCPtr.hpp"
 #include "../NBT/CompoundTag.hpp"
@@ -43,7 +44,18 @@ class Chunk : public std::shared_ptr<const NBT::CompoundTag> {
 public:
 	static const size_t SIZE = 16;
 
+	struct Blocks {
+		Block blocks[SIZE][SIZE];
+	};
+
 private:
+	static size_t getIndex(size_t x, size_t y, size_t z) {
+		if (x >= SIZE || y >= SIZE || z >= SIZE)
+			throw std::range_error("Chunk::getIndex(): bad coordinates");
+
+		return 256*y + 16*z + x;
+	}
+
 	size_t len;
 	UniqueCPtr<uint8_t[]> data;
 
@@ -56,15 +68,8 @@ private:
 	void parseChunk();
 	void analyzeChunk();
 
-	size_t getIndex(size_t x, size_t y, size_t z) {
-		if (x >= SIZE || y >= SIZE || z >= SIZE)
-			throw std::range_error("Chunk::getIndex(): bad coordinates");
-
-		return 256*y + 16*z + x;
-	}
-
-	uint8_t getBlockAt(const std::shared_ptr<const NBT::CompoundTag> &section, size_t x, size_t y, size_t z);
-	uint8_t getDataAt(const std::shared_ptr<const NBT::CompoundTag> &section, size_t x, size_t y, size_t z);
+	uint8_t getBlockAt(const std::shared_ptr<const NBT::CompoundTag> &section, size_t x, size_t y, size_t z) const;
+	uint8_t getDataAt(const std::shared_ptr<const NBT::CompoundTag> &section, size_t x, size_t y, size_t z) const;
 
 public:
 	Chunk(Buffer buffer);
@@ -72,6 +77,8 @@ public:
 	const NBT::ListTag<NBT::CompoundTag> & getSections() const {
 		return *sections;
 	}
+
+	Blocks getTopLayer() const;
 };
 
 }