From b6f14f0c72ecbc2bc255861bbb3982352177eccb Mon Sep 17 00:00:00 2001
From: Matthias Schiffer <mschiffer@universe-factory.net>
Date: Tue, 24 Jul 2018 20:31:53 +0200
Subject: Add support for Minecraft 1.13 sections

---
 src/World/Section.cpp | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++
 src/World/Section.hpp | 24 ++++++++++++++++++++++
 2 files changed, 80 insertions(+)

diff --git a/src/World/Section.cpp b/src/World/Section.cpp
index 6f06435..fbf1c33 100644
--- a/src/World/Section.cpp
+++ b/src/World/Section.cpp
@@ -26,8 +26,11 @@
 
 #include "Section.hpp"
 #include "../NBT/ByteTag.hpp"
+#include "../NBT/StringTag.hpp"
 #include "../Util.hpp"
 
+#include <cstdio>
+
 
 namespace MinedMap {
 namespace World {
@@ -39,12 +42,20 @@ Section::Section(const std::shared_ptr<const NBT::CompoundTag> &section) {
 
 
 std::unique_ptr<Section> Section::makeSection(const std::shared_ptr<const NBT::CompoundTag> &section) {
+	std::shared_ptr<const NBT::LongArrayTag> blockStates = section->get<NBT::LongArrayTag>("BlockStates");
+	if (blockStates) {
+		const std::shared_ptr<const NBT::ListTag> palette = assertValue(section->get<NBT::ListTag>("Palette"));
+
+		return std::unique_ptr<Section>(new PaletteSection(section, std::move(blockStates), palette));
+	}
+
 	std::shared_ptr<const NBT::ByteArrayTag> blocks = assertValue(section->get<NBT::ByteArrayTag>("Blocks"));
 	std::shared_ptr<const NBT::ByteArrayTag> data = assertValue(section->get<NBT::ByteArrayTag>("Data"));
 
 	return std::unique_ptr<Section>(new LegacySection(section, std::move(blocks), std::move(data)));
 }
 
+
 const Resource::BlockType * LegacySection::getBlockStateAt(size_t x, size_t y, size_t z) const {
 	uint8_t type = getBlockAt(x, y, z);
 	uint8_t data = getDataAt(x, y, z);
@@ -52,5 +63,50 @@ const Resource::BlockType * LegacySection::getBlockStateAt(size_t x, size_t y, s
 	return Resource::LEGACY_BLOCK_TYPES.types[type][data];
 }
 
+
+PaletteSection::PaletteSection(
+	const std::shared_ptr<const NBT::CompoundTag> &section,
+	std::shared_ptr<const NBT::LongArrayTag> &&blockStates0,
+	const std::shared_ptr<const NBT::ListTag> &paletteData
+) : Section(section), blockStates(blockStates0) {
+	if (blockStates->getLength() % 64)
+		throw std::invalid_argument("corrupt section data");
+
+	bits = blockStates->getLength() / 64;
+	if (bits > 16)
+		throw std::invalid_argument("unsupported block state bits");
+
+	mask = (1u << bits) - 1;
+
+
+	for (const auto &entry : *paletteData) {
+		const NBT::CompoundTag &paletteEntry = *assertValue(dynamic_cast<const NBT::CompoundTag *>(entry.get()));
+		std::string name = assertValue(paletteEntry.get<NBT::StringTag>("Name"))->getValue();
+
+		const Resource::BlockType *type = Resource::BlockType::lookup(name);
+		if (!type)
+			std::fprintf(stderr, "Warning: unknown block type: %s\n", name.c_str());
+
+		palette.push_back(type);
+	}
+}
+
+const Resource::BlockType * PaletteSection::getBlockStateAt(size_t x, size_t y, size_t z) const {
+	size_t index = bits * getIndex(x, y, z);
+	size_t pos = index >> 3;
+	size_t shift = index & 7;
+
+	uint32_t v = blockStates->getPointer()[mangleByteIndex(pos)];
+
+	if (shift + bits > 8)
+		v |= blockStates->getPointer()[mangleByteIndex(pos + 1)] << 8;
+	if (shift + bits > 16)
+		v |= blockStates->getPointer()[mangleByteIndex(pos + 2)] << 16;
+	/* We do not need to check for shift+bits > 24: bits should never
+	be greater than 12, so our value will never span more than 3 bytes */
+
+	return palette.at((v >> shift) & mask);
+}
+
 }
 }
diff --git a/src/World/Section.hpp b/src/World/Section.hpp
index a4686e3..3444bce 100644
--- a/src/World/Section.hpp
+++ b/src/World/Section.hpp
@@ -29,6 +29,8 @@
 
 #include "../NBT/ByteArrayTag.hpp"
 #include "../NBT/CompoundTag.hpp"
+#include "../NBT/ListTag.hpp"
+#include "../NBT/LongArrayTag.hpp"
 #include "../Resource/BlockType.hpp"
 
 #include <cstdint>
@@ -106,5 +108,27 @@ public:
 	virtual const Resource::BlockType * getBlockStateAt(size_t x, size_t y, size_t z) const;
 };
 
+class PaletteSection : public Section {
+private:
+	std::shared_ptr<const NBT::LongArrayTag> blockStates;
+	std::vector<const Resource::BlockType *> palette;
+	size_t bits;
+	uint16_t mask;
+
+
+	static size_t mangleByteIndex(size_t index) {
+		return (index & ~(size_t)7) + 7 - (index & 7);
+	}
+
+public:
+	PaletteSection(
+		const std::shared_ptr<const NBT::CompoundTag> &section,
+		std::shared_ptr<const NBT::LongArrayTag> &&blockStates0,
+		const std::shared_ptr<const NBT::ListTag> &paletteData
+	);
+
+	virtual const Resource::BlockType * getBlockStateAt(size_t x, size_t y, size_t z) const;
+};
+
 }
 }
-- 
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