chunk reading: check early if data is empty

Now it does not allocate chunk data when the section is truly empty (servers sometimes send the opposite and then it turns out that they are empty)

src/main/java/de/bixilon/minosoft/data/world/container/palette/PalettedContainerReader.kt

@@ -15,6 +15,7 @@ package de.bixilon.minosoft.data.world.container.palette
 
 import de.bixilon.minosoft.data.registries.registries.registry.AbstractRegistry
 import de.bixilon.minosoft.data.world.container.palette.data.PaletteData
+import de.bixilon.minosoft.data.world.container.palette.palettes.BlockStatePaletteFactory
 import de.bixilon.minosoft.data.world.container.palette.palettes.PaletteFactory
 import de.bixilon.minosoft.protocol.protocol.buffers.play.PlayInByteBuffer
 
@@ -41,16 +42,27 @@ object PalettedContainerReader {
         val data = PaletteData.create(buffer.versionId, palette.bits, factory.containerSize)
         try {
             data.read(buffer)
+            if (factory == BlockStatePaletteFactory && data.isEmpty) { // id 0 is air
+                return null
+            }
             val container = PalettedContainer(factory.edgeBits, palette, data)
 
             if (container.isEmpty) return null
             val unpacked = container.unpack<T>()
 
-            if (unpacked.isEmpty()) return null
+            if (unpacked.isAllNull()) return null
 
             return unpacked
         } finally {
             data.free()
         }
     }
+
+    fun <T> Array<T>.isAllNull(): Boolean {
+        for (entry in this) {
+            if (entry == null) continue
+            return false
+        }
+        return true
+    }
 }

src/main/java/de/bixilon/minosoft/data/world/container/palette/data/EmptyPaletteData.kt

@@ -16,6 +16,7 @@ package de.bixilon.minosoft.data.world.container.palette.data
 import de.bixilon.minosoft.protocol.protocol.buffers.play.PlayInByteBuffer
 
 class EmptyPaletteData(override val size: Int) : PaletteData {
+    override val isEmpty: Boolean get() = true
 
     override fun free() = Unit
 

src/main/java/de/bixilon/minosoft/data/world/container/palette/data/PaletteData.kt

@@ -17,6 +17,7 @@ import de.bixilon.minosoft.data.world.container.palette.data.array.ArrayPaletteD
 import de.bixilon.minosoft.protocol.protocol.buffers.play.PlayInByteBuffer
 
 interface PaletteData {
+    val isEmpty: Boolean
     val size: Int
 
     fun get(index: Int): Int

src/main/java/de/bixilon/minosoft/data/world/container/palette/data/array/ArrayPaletteData.kt

@@ -27,25 +27,40 @@ class ArrayPaletteData(
     private val valuesPerLong = Long.SIZE_BITS / elementBits
     private lateinit var data: LongArray
 
+    override var isEmpty = true
+
     init {
         check(elementBits in 0..32)
     }
 
-    override fun read(buffer: PlayInByteBuffer) {
-        val packetSize = buffer.readVarInt()
-        val size: Int = if (versionId < LONG_BIT_SPLITTING_VERSION) {
+    private fun calculateLongs(): Int {
+        if (versionId < LONG_BIT_SPLITTING_VERSION) {
             val bits = this.size * elementBits
 
-            (bits + (Long.SIZE_BITS - 1)) / Long.SIZE_BITS // divide up
-        } else {
-            (this.size + valuesPerLong - 1) / valuesPerLong
+            return (bits + (Long.SIZE_BITS - 1)) / Long.SIZE_BITS // divide up
         }
-        this.data = ALLOCATOR.allocate(this.size)
-        if (packetSize != size) {
+        return (this.size + valuesPerLong - 1) / valuesPerLong
+    }
+
+    private fun checkEmpty(size: Int): Boolean {
+        for (i in 0 until size) {
+            if (this.data[i] != 0L) {
+                return false
+            }
+        }
+        return true
+    }
+
+    override fun read(buffer: PlayInByteBuffer) {
+        val packetSize = buffer.readVarInt()
+        val longs = calculateLongs()
+        this.data = ALLOCATOR.allocate(longs)
+        if (packetSize != longs) {
             buffer.pointer += packetSize * Long.SIZE_BYTES // data is ignored
             return
         }
-        buffer.readLongArray(this.data, size)
+        buffer.readLongArray(this.data, longs)
+        this.isEmpty = checkEmpty(longs)
     }
 
     override operator fun get(index: Int): Int {

src/main/java/de/bixilon/minosoft/protocol/packets/s2c/play/block/chunk/ChunkUtil.kt

@@ -305,12 +305,4 @@ object ChunkUtil {
     fun ChunkPosition.isInViewDistance(viewDistance: Int, cameraPosition: ChunkPosition): Boolean {
         return abs(this.x - cameraPosition.x) <= viewDistance && abs(this.y - cameraPosition.y) <= viewDistance
     }
-
-    private fun Array<BlockState?>.isEmpty(): Boolean {
-        for (entry in this) {
-            if (entry == null) continue
-            return false
-        }
-        return true
-    }
 }