introduce compressed_chunks namespace

src/voxels/compressed_chunks.cpp

@@ -0,0 +1,61 @@
+#include "compressed_chunks.hpp"
+
+#include "coders/rle.hpp"
+#include "coders/gzip.hpp"
+#include "coders/byte_utils.hpp"
+#include "voxels/Chunk.hpp"
+
+inline constexpr int HAS_VOXELS = 0x1;
+inline constexpr int HAS_METADATA = 0x2;
+
+std::vector<ubyte> compressed_chunks::encode(const Chunk& chunk) {
+    auto data = chunk.encode();
+
+    /// world.get_chunk_data is only available in the main Lua state
+    static util::Buffer<ubyte> rleBuffer;
+    if (rleBuffer.size() < CHUNK_DATA_LEN * 2) {
+        rleBuffer = util::Buffer<ubyte>(CHUNK_DATA_LEN * 2);
+    }
+    size_t rleCompressedSize =
+        extrle::encode16(data.get(), CHUNK_DATA_LEN, rleBuffer.data());
+
+    const auto gzipCompressedData = gzip::compress(
+        rleBuffer.data(), rleCompressedSize
+    );
+    auto metadataBytes = chunk.blocksMetadata.serialize();
+
+    ByteBuilder builder(2 + 8 + gzipCompressedData.size() + metadataBytes.size());
+    builder.put(HAS_VOXELS | HAS_METADATA); // flags
+    builder.put(0); // reserved
+    builder.putInt32(gzipCompressedData.size());
+    builder.put(gzipCompressedData.data(), gzipCompressedData.size());
+    builder.putInt32(metadataBytes.size());
+    builder.put(metadataBytes.data(), metadataBytes.size());
+    return builder.build();
+}
+
+void compressed_chunks::decode(Chunk& chunk, const ubyte* src, size_t size) {
+    ByteReader reader(src, size);
+
+    ubyte flags = reader.get();
+    reader.skip(1); // reserved byte
+
+    if (flags & HAS_VOXELS) {
+        size_t gzipCompressedSize = reader.getInt32();
+        
+        auto rleData = gzip::decompress(reader.pointer(), gzipCompressedSize);
+        reader.skip(gzipCompressedSize);
+
+        /// world.get_chunk_data is only available in the main Lua state
+        static util::Buffer<ubyte> voxelData (CHUNK_DATA_LEN);
+        extrle::decode16(rleData.data(), rleData.size(), voxelData.data());
+        chunk.decode(voxelData.data());
+        chunk.updateHeights();
+    }
+    if (flags & HAS_METADATA) {
+        size_t metadataSize = reader.getInt32();
+        chunk.blocksMetadata.deserialize(reader.pointer(), metadataSize);
+        reader.skip(metadataSize);
+    }
+    chunk.setModifiedAndUnsaved();
+}