feat: Added the generate command to load existing world saves

world/chunk_data.go

@@ -0,0 +1,75 @@
+package world
+
+import (
+	"github.com/Tnze/go-mc/save"
+)
+
+const ChunkSectionCount = 16
+
+type ChunkData struct {
+	Pos      ChunkPos                        `json:"pos"`
+	Sections [ChunkSectionCount]ChunkSection `json:"sections"`
+}
+
+func (cd *ChunkData) SectionFor(pos BlockPos) *ChunkSection {
+	return &cd.Sections[pos.Y%ChunkSectionCount]
+}
+
+func extractPaletteIndexes(compressed int64) [16]byte {
+	var outputs [16]byte
+	var outputIndex int
+
+	for index := 0; index < 64; index += 4 {
+		shifted := compressed >> index
+		// Mask off the lowest four bits
+		shifted &= 0xf
+		outputs[outputIndex] = byte(shifted)
+		outputIndex += 1
+	}
+
+	return outputs
+}
+
+func (cd *ChunkData) FromMCAChunk(other save.Chunk) {
+	// Load the chunk's position
+	cd.Pos = ChunkPos{X: int(other.XPos), Z: int(other.ZPos)}
+
+	// Load the data from the chunk
+	for sectionIndex, section := range other.Sections {
+		// TODO: Enable chunks to have more than 16 sections
+		if sectionIndex >= ChunkSectionCount {
+			break
+		}
+
+		var currentSection ChunkSection
+
+		paletteIndexes := []int{}
+		for _, compress := range section.BlockStates.Data {
+			indexes := extractPaletteIndexes(int64(compress))
+
+			converted := make([]int, 16)
+			for i := 0; i < 16; i++ {
+				converted[i] = int(indexes[i])
+			}
+
+			paletteIndexes = append(paletteIndexes, converted...)
+		}
+
+		for blockIndex, paletteIndex := range paletteIndexes {
+			var state BlockID
+			if section.BlockStates.Palette[paletteIndex].Name == "minecraft:air" {
+				state = Empty
+			} else {
+				cd.Sections[sectionIndex].BlockCount += 1
+				state = Generic
+			}
+
+			// TODO: Remove this workaround for larger bit sizes in palettes
+			if blockIndex < 4096 {
+				currentSection.BlockStates[blockIndex] = state
+			}
+		}
+
+		cd.Sections[sectionIndex] = currentSection
+	}
+}

world/data_format.go

@@ -31,15 +31,6 @@ func (b BlockPos) ToChunkPos() ChunkPos {
 	}
 }
 
-type ChunkData struct {
-	Pos      ChunkPos         `json:"pos"`
-	Sections [16]ChunkSection `json:"sections"`
-}
-
-func (cd *ChunkData) SectionFor(pos BlockPos) *ChunkSection {
-	return &cd.Sections[pos.Y%16]
-}
-
 type ChunkPos struct {
 	X int `json:"x"`
 	Z int `json:"z"`