Re-write QuickReplaySender caching to be significantly more memory efficient

src/main/java/com/replaymod/replay/QuickReplaySender.java

@@ -32,6 +32,8 @@ import com.github.steveice10.packetlib.io.NetInput;
 import com.github.steveice10.packetlib.io.NetOutput;
 import com.github.steveice10.packetlib.io.stream.StreamNetInput;
 import com.github.steveice10.packetlib.io.stream.StreamNetOutput;
+import com.github.steveice10.packetlib.tcp.io.ByteBufNetInput;
+import com.github.steveice10.packetlib.tcp.io.ByteBufNetOutput;
 import com.google.common.base.Optional;
 import com.google.common.collect.ListMultimap;
 import com.google.common.collect.Multimaps;
@@ -53,6 +55,7 @@ import io.netty.buffer.Unpooled;
 import io.netty.channel.ChannelHandler;
 import io.netty.channel.ChannelHandlerAdapter;
 import io.netty.channel.ChannelHandlerContext;
+import lombok.SneakyThrows;
 import net.minecraft.client.Minecraft;
 import net.minecraft.network.EnumConnectionState;
 import net.minecraft.network.EnumPacketDirection;
@@ -95,6 +98,7 @@ import static com.replaymod.replay.ReplayModReplay.LOGGER;
 @ChannelHandler.Sharable
 public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySender {
     private static final String CACHE_ENTRY = "quickModeCache.bin";
+    private static final String CACHE_INDEX_ENTRY = "quickModeCacheIndex.bin";
     private static final int CACHE_VERSION = 0;
 
     private final Minecraft mc = Minecraft.getMinecraft();
@@ -115,6 +119,8 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
 
     private ListenableFuture<Void> initPromise;
 
+    private com.github.steveice10.netty.buffer.ByteBuf buf;
+    private NetInput bufInput;
     private TreeMap<Integer, Collection<BakedTrackedThing>> thingSpawnsT = new TreeMap<>();
     private ListMultimap<Integer, BakedTrackedThing> thingSpawns = Multimaps.newListMultimap(thingSpawnsT, ArrayList::new);
     private TreeMap<Integer, Collection<BakedTrackedThing>> thingDespawnsT = new TreeMap<>();
@@ -207,7 +213,7 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
     public void setReplaySpeed(double factor) {
         if (factor != 0) {
             if (paused() && asyncMode) {
-                lastAsyncUpdateTime = System.currentTimeMillis(); // TODO test this
+                lastAsyncUpdateTime = System.currentTimeMillis();
             }
             this.replaySpeed = factor;
         }
@@ -263,49 +269,63 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
     }
 
     private boolean tryLoadFromCache(Consumer<Double> progress) throws IOException {
-        Optional<InputStream> cacheOpt = replayFile.get(CACHE_ENTRY);
+        boolean success = false;
-        if (!cacheOpt.isPresent()) return false;
-        boolean success = loadFromCache(cacheOpt.get(), progress);
-        if (!success) {
-            thingSpawnsT.clear();
-            thingDespawnsT.clear();
-            worldTimes.clear();
-            thunderStrengths.clear();
-        }
-        return success;
-    }
 
-    private boolean loadFromCache(InputStream rawIn, Consumer<Double> progress) throws IOException {
+        Optional<InputStream> cacheIndexOpt = replayFile.get(CACHE_INDEX_ENTRY);
-        long sysTimeStart = System.currentTimeMillis();
+        if (!cacheIndexOpt.isPresent()) return false;
-        NetInput in = new StreamNetInput(rawIn);
+        try (InputStream indexIn = cacheIndexOpt.get()) {
-        int version = in.readVarInt();
+            Optional<InputStream> cacheOpt = replayFile.get(CACHE_ENTRY);
-        if (version > CACHE_VERSION) return false; // More recent than this version, no chance we can read that
+            if (!cacheOpt.isPresent()) return false;
-
+            try (InputStream cacheIn = cacheOpt.get()) {
-        int size = in.readVarInt();
+                success = loadFromCache(cacheIn, indexIn, progress);
-        int spawnTime = 0;
+            }
-        for (int i = 0; i < size; i++) {
+        } finally {
-            progress.accept((double) i / size);
+            if (!success) {
-            spawnTime += in.readVarInt();
+                buf = null;
-            for (int j = in.readVarInt(); j > 0; j--) {
+                bufInput = null;
-                int despawnTime = in.readVarInt();
+                thingSpawnsT.clear();
-                BakedTrackedThing trackedThing;
+                thingDespawnsT.clear();
-                switch (in.readVarInt()) {
+                worldTimes.clear();
-                    case 0: trackedThing = new BakedEntity(version, in); break;
+                thunderStrengths.clear();
-                    case 1: trackedThing = new BakedChunk(version, in); break;
-                    case 2: trackedThing = new BakedWeather(version, in); break;
-                    default: return false;
-                }
-                trackedThing.spawnTime = spawnTime;
-                trackedThing.despawnTime = despawnTime;
-                thingSpawns.put(spawnTime, trackedThing);
-                thingDespawns.put(despawnTime, trackedThing);
             }
         }
 
-        // These should go quick, they probably won't need to update progress
+        return success;
-        progress.accept(1.0);
+    }
-        readFromCache(version, in, worldTimes);
+
-        readFromCache(version, in, thunderStrengths);
+    private boolean loadFromCache(InputStream cacheIn, InputStream rawIndexIn, Consumer<Double> progress) throws IOException {
+        long sysTimeStart = System.currentTimeMillis();
+
+        NetInput in = new StreamNetInput(rawIndexIn);
+        if (in.readVarInt() != CACHE_VERSION) return false; // Incompatible cache version
+        if (new StreamNetInput(cacheIn).readVarInt() != CACHE_VERSION) return false; // Incompatible cache version
+
+        things: while (true) {
+            BakedTrackedThing trackedThing;
+            switch (in.readVarInt()) {
+                case 0: break things;
+                case 1: trackedThing = new BakedEntity(in); break;
+                case 2: trackedThing = new BakedChunk(in); break;
+                case 3: trackedThing = new BakedWeather(in); break;
+                default: return false;
+            }
+            thingSpawns.put(trackedThing.spawnTime, trackedThing);
+            thingDespawns.put(trackedThing.despawnTime, trackedThing);
+        }
+
+        readFromCache(in, worldTimes);
+        readFromCache(in, thunderStrengths);
+        int size = in.readVarInt();
+
+        buf = com.github.steveice10.netty.buffer.Unpooled.buffer(size);
+        int read = 0;
+        while (true) {
+            int len = buf.writeBytes(cacheIn, Math.min(size - read, 4096));
+            if (len <= 0) break;
+            read += len;
+            progress.accept((double) read / size);
+        }
+        bufInput = new ByteBufNetInput(buf);
 
         LOGGER.info("Loaded quick replay from cache in " + (System.currentTimeMillis() - sysTimeStart) + "ms");
         return true;
@@ -327,8 +347,6 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
         studio.setParsing(ServerUpdateTimePacket.class, true);
         studio.setParsing(ServerNotifyClientPacket.class, true);
 
-        TreeMap<Integer, Collection<TrackedThing>> thingSpawnsT = new TreeMap<>();
-        ListMultimap<Integer, TrackedThing> thingSpawns = Multimaps.newListMultimap(thingSpawnsT, ArrayList::new);
         TreeMap<Integer, com.github.steveice10.packetlib.packet.Packet> worldTimes = new TreeMap<>();
         TreeMap<Integer, com.github.steveice10.packetlib.packet.Packet> thunderStrengths = new TreeMap<>();
         Map<UUID, PlayerListEntry> playerListEntries = new HashMap<>();
@@ -336,33 +354,33 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
         Map<Long, Chunk> activeChunks = new HashMap<>();
         Weather activeWeather = null;
 
-        // 90% of estimated time are for analysis, 10% for writing cache
-        // This heuristic is based on simply running the function on some 3h replay.
-        // Numbers may be significantly different for smaller replays where GC doesn't kick in. But the progress bar
-        // will hopefully be barely visible in that case anyway.
-        // May need to be updated when performance of MCProtocolLib or this code is improved.
-        // Same for the split between analyseReplay and loadFromCache declared in #initialize(...)
-        final double progressSplit = 0.9;
-
         double sysTimeStart = System.currentTimeMillis();
         double duration;
-        try (ReplayInputStream in = replayFile.getPacketData(studio)) {
+        try (ReplayInputStream in = replayFile.getPacketData(studio);
+             OutputStream cacheOut = replayFile.write(CACHE_ENTRY);
+             OutputStream cacheIndexOut = replayFile.write(CACHE_INDEX_ENTRY)) {
+            NetOutput out = new StreamNetOutput(cacheOut);
+            out.writeVarInt(CACHE_VERSION);
+            NetOutput indexOut = new StreamNetOutput(cacheIndexOut);
+            indexOut.writeVarInt(CACHE_VERSION);
+
+            int index = 0;
+            int time = 0;
             duration = replayFile.getMetaData().getDuration();
             PacketData packetData;
             while ((packetData = in.readPacket()) != null) {
                 com.github.steveice10.packetlib.packet.Packet packet = packetData.getPacket();
-                int time = (int) packetData.getTime();
+                time = (int) packetData.getTime();
-                progress.accept(time / duration * progressSplit);
+                progress.accept(time / duration);
                 Integer entityId = PacketUtils.getEntityId(packet);
                 if (packet instanceof ServerSpawnMobPacket
                         || packet instanceof ServerSpawnObjectPacket
                         || packet instanceof ServerSpawnPaintingPacket) {
                     Entity entity = new Entity(entityId, Collections.singletonList(packet));
                     entity.spawnTime = time;
-                    thingSpawns.put(time, entity);
                     Entity prev = activeEntities.put(entityId, entity);
                     if (prev != null) {
-                        prev.despawnTime = time;
+                        index = prev.writeToCache(indexOut, out, time, index);
                     }
                 } else if (packet instanceof ServerSpawnPlayerPacket) {
                     ServerPlayerListEntryPacket listEntryPacket = new ServerPlayerListEntryPacket(
@@ -373,34 +391,30 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
                     );
                     Entity entity = new Entity(entityId, Arrays.asList(listEntryPacket, packet));
                     entity.spawnTime = time;
-                    thingSpawns.put(time, entity);
                     Entity prev = activeEntities.put(entityId, entity);
                     if (prev != null) {
-                        prev.despawnTime = time;
+                        index = prev.writeToCache(indexOut, out, time, index);
                     }
                 } else if (packet instanceof ServerEntityDestroyPacket) {
                     for (int id : ((ServerEntityDestroyPacket) packet).getEntityIds()) {
                         Entity entity = activeEntities.remove(id);
                         if (entity != null) {
-                            entity.despawnTime = time;
+                            index = entity.writeToCache(indexOut, out, time, index);
                         }
                     }
                 } else if (packet instanceof ServerChunkDataPacket) {
                     Column column = ((ServerChunkDataPacket) packet).getColumn();
                     Chunk chunk = new Chunk(column);
                     chunk.spawnTime = time;
-                    thingSpawns.put(time, chunk);
                     Chunk prev = activeChunks.put(coordToLong(column.getX(), column.getZ()), chunk);
                     if (prev != null) {
-                        prev.currentBlockState = null; // free memory because we no longer need it
+                        index = prev.writeToCache(indexOut, out, time, index);
-                        prev.despawnTime = time;
                     }
                 } else if (packet instanceof ServerUnloadChunkPacket) {
                     ServerUnloadChunkPacket p = (ServerUnloadChunkPacket) packet;
                     Chunk prev = activeChunks.remove(coordToLong(p.getX(), p.getZ()));
                     if (prev != null) {
-                        prev.currentBlockState = null; // free memory because we no longer need it
+                        index = prev.writeToCache(indexOut, out, time, index);
-                        prev.despawnTime = time;
                     }
                 } else if (packet instanceof ServerBlockChangePacket || packet instanceof ServerMultiBlockChangePacket) {
                     for (BlockChangeRecord record :
@@ -426,12 +440,16 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
                         }
                     }
                 } else if (packet instanceof ServerRespawnPacket) {
-                    activeEntities.values().forEach(entity -> entity.despawnTime = time);
+                    for (Entity entity : activeEntities.values()) {
+                        index = entity.writeToCache(indexOut, out, time, index);
+                    }
                     activeEntities.clear();
-                    activeChunks.values().forEach(chunk -> chunk.despawnTime = time);
+                    for (Chunk chunk : activeChunks.values()) {
+                        index = chunk.writeToCache(indexOut, out, time, index);
+                    }
                     activeChunks.clear();
                     if (activeWeather != null) {
-                        activeWeather.despawnTime = time;
+                        index = activeWeather.writeToCache(indexOut, out, time, index);
                     }
                     activeWeather = null;
                 } else if (packet instanceof ServerUpdateTimePacket) {
@@ -441,15 +459,14 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
                     switch (p.getNotification()) {
                         case START_RAIN:
                             if (activeWeather != null) {
-                                activeWeather.despawnTime = time;
+                                index = activeWeather.writeToCache(indexOut, out, time, index);
                             }
                             activeWeather = new Weather();
                             activeWeather.spawnTime = time;
-                            thingSpawns.put(time, activeWeather);
                             break;
                         case STOP_RAIN:
                             if (activeWeather != null) {
-                                activeWeather.despawnTime = time;
+                                index = activeWeather.writeToCache(indexOut, out, time, index);
                                 activeWeather = null;
                             }
                             break;
@@ -475,43 +492,24 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
                     }
                 }
             }
+
+            for (Entity entity : activeEntities.values()) {
+                index = entity.writeToCache(indexOut, out, time, index);
+            }
+            for (Chunk chunk : activeChunks.values()) {
+                index = chunk.writeToCache(indexOut, out, time, index);
+            }
+            if (activeWeather != null) {
+                index = activeWeather.writeToCache(indexOut, out, time, index);
+            }
+
+            indexOut.writeByte(0);
+            writeToCache(indexOut, worldTimes);
+            writeToCache(indexOut, thunderStrengths);
+
+            indexOut.writeVarInt(index);
         }
         LOGGER.info("Analysed replay in " + (System.currentTimeMillis() - sysTimeStart) + "ms");
-
-        sysTimeStart = System.currentTimeMillis();
-        try (OutputStream cacheOut = replayFile.write(CACHE_ENTRY)) {
-            NetOutput out = new StreamNetOutput(cacheOut);
-            out.writeVarInt(CACHE_VERSION);
-
-            out.writeVarInt(thingSpawnsT.size());
-            int lastTime = 0;
-            for (Map.Entry<Integer, Collection<TrackedThing>> entry : thingSpawnsT.entrySet()) {
-                int time = entry.getKey();
-                out.writeVarInt(time - lastTime);
-                lastTime = time;
-
-                progress.accept(time / duration * (1 - progressSplit) + progressSplit);
-
-                Collection<TrackedThing> trackedThings = entry.getValue();
-                out.writeVarInt(trackedThings.size());
-                for (TrackedThing trackedThing : trackedThings) {
-                    out.writeVarInt(trackedThing.despawnTime);
-                    if (trackedThing instanceof Entity) {
-                        out.writeVarInt(0);
-                    } else if (trackedThing instanceof Chunk) {
-                        out.writeVarInt(1);
-                    } else if (trackedThing instanceof Weather) {
-                        out.writeVarInt(2);
-                    } else {
-                        throw new UnsupportedOperationException("Unknown type of tracked thing: " + trackedThing);
-                    }
-                    trackedThing.writeToCache(out);
-                }
-            }
-            writeToCache(out, worldTimes);
-            writeToCache(out, thunderStrengths);
-        }
-        LOGGER.info("Wrote quick replay to cache in " + (System.currentTimeMillis() - sysTimeStart) + "ms");
     }
 
     @Override
@@ -519,8 +517,8 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
         ensureInitialized(() -> {
             if (replayTime > currentTimeStamp) {
                 activeThings.removeIf(thing -> {
-                    if (thing.despawnTime < replayTime) {
+                    if (thing.despawnTime <= replayTime) {
-                        thing.despawnPackets.forEach(ctx::fireChannelRead);
+                        thing.despawn(this, ctx::fireChannelRead);
                         return true;
                     } else {
                         return false;
@@ -529,7 +527,7 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
                 thingSpawnsT.subMap(currentTimeStamp, false, replayTime, true).values()
                         .forEach(things -> things.forEach(thing -> {
                             if (thing.despawnTime > replayTime) {
-                                thing.spawnPackets.forEach(ctx::fireChannelRead);
+                                thing.spawn(this, ctx::fireChannelRead);
                                 activeThings.add(thing);
                             }
                         }));
@@ -539,7 +537,7 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
             } else {
                 activeThings.removeIf(thing -> {
                     if (thing.spawnTime > replayTime) {
-                        thing.despawnPackets.forEach(ctx::fireChannelRead);
+                        thing.despawn(this, ctx::fireChannelRead);
                         return true;
                     } else {
                         return false;
@@ -548,7 +546,7 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
                 thingDespawnsT.subMap(replayTime, false, currentTimeStamp, true).values()
                         .forEach(things -> things.forEach(thing -> {
                             if (thing.spawnTime <= replayTime) {
-                                thing.spawnPackets.forEach(ctx::fireChannelRead);
+                                thing.spawn(this, ctx::fireChannelRead);
                                 activeThings.add(thing);
                             }
                         }));
@@ -560,6 +558,25 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
         });
     }
 
+    private static final com.github.steveice10.netty.buffer.ByteBuf mcplByteBuf = com.github.steveice10.netty.buffer.Unpooled.buffer();
+    private static final ByteBufNetInput byteBufNetInput = new ByteBufNetInput(mcplByteBuf);
+    private static final ByteBufNetOutput byteBufNetOutput = new ByteBufNetOutput(mcplByteBuf);
+
+    private static BlockStorage copy(BlockStorage of) {
+        int readerIndex = byteBuf.readerIndex(); // Mark the current reader and writer index (should be at start)
+        int writerIndex = byteBuf.writerIndex();
+        try {
+            of.write(byteBufNetOutput);
+            return new BlockStorage(byteBufNetInput);
+        } catch (Exception e) {
+            Utils.throwIfUnchecked(e);
+            throw new RuntimeException(e);
+        } finally {
+            byteBuf.readerIndex(readerIndex); // Reset reader & writer index for next use
+            byteBuf.writerIndex(writerIndex);
+        }
+    }
+
     private static final ByteBuf byteBuf = Unpooled.buffer();
     private static final ByteBufOutputStream byteBufOut = new ByteBufOutputStream(byteBuf);
     private static final PacketBuffer packetBuf = new PacketBuffer(byteBuf);
@@ -597,7 +614,7 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
         }
     }
 
-    private static Packet<?> readPacketFromCache(int version, NetInput in) throws IOException {
+    private static Packet<?> readPacketFromCache(NetInput in) throws IOException {
         int readerIndex = byteBuf.readerIndex(); // Mark the current reader and writer index (should be at start)
         int writerIndex = byteBuf.writerIndex();
         try {
@@ -622,24 +639,25 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
         }
     }
 
-    private static List<Packet<?>> readPacketsFromCache(int version, NetInput in) throws IOException {
+    @SneakyThrows(IOException.class)
+    private static List<Packet<?>> readPacketsFromCache(NetInput in) {
         int size = in.readVarInt();
         List<Packet<?>> packets = new ArrayList<>(size);
         for (int i = 0; i < size; i++) {
-            packets.add(readPacketFromCache(version, in));
+            packets.add(readPacketFromCache(in));
         }
         return packets;
     }
 
-    private static void readFromCache(int version, NetInput in, SortedMap<Integer, Packet<?>> packets) throws IOException {
+    private static void readFromCache(NetInput in, SortedMap<Integer, Packet<?>> packets) throws IOException {
         int time = 0;
         for (int i = in.readVarInt(); i > 0; i--) {
             time += in.readVarInt();
-            packets.put(time, readPacketFromCache(version, in));
+            packets.put(time, readPacketFromCache(in));
         }
     }
 
-    private static void writeToCache(NetOutput out, com.github.steveice10.packetlib.packet.Packet packet) throws IOException {
+    private static int writeToCache(NetOutput out, com.github.steveice10.packetlib.packet.Packet packet) throws IOException {
         int readerIndex = byteBuf.readerIndex(); // Mark the current reader and writer index (should be at start)
         int writerIndex = byteBuf.writerIndex();
         try {
@@ -649,10 +667,11 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
             byteBuf.skipBytes(8); // Skip packet length & timestamp
 
             int size = byteBuf.readableBytes();
-            out.writeVarInt(size);
+            int len = writeVarInt(out, size);
             for (int i = 0; i < size; i++) {
                 out.writeByte(byteBuf.readByte());
             }
+            return len + size;
         } catch (Exception e) {
             Utils.throwIfInstanceOf(e, IOException.class);
             Utils.throwIfUnchecked(e);
@@ -663,23 +682,37 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
         }
     }
 
-    private static void writeToCache(NetOutput out, Collection<com.github.steveice10.packetlib.packet.Packet> packets) throws IOException {
+    private static int writeToCache(NetOutput out, Collection<com.github.steveice10.packetlib.packet.Packet> packets) throws IOException {
-        out.writeVarInt(packets.size());
+        int len = writeVarInt(out, packets.size());
         for (com.github.steveice10.packetlib.packet.Packet packet : packets) {
-            writeToCache(out, packet);
+            len += writeToCache(out, packet);
         }
+        return len;
     }
 
-    private static void writeToCache(NetOutput out, SortedMap<Integer, com.github.steveice10.packetlib.packet.Packet> packets) throws IOException {
+    private static int writeToCache(NetOutput out, SortedMap<Integer, com.github.steveice10.packetlib.packet.Packet> packets) throws IOException {
-        out.writeVarInt(packets.size());
+        int len = 0;
+        len += writeVarInt(out, packets.size());
         int lastTime = 0;
         for (Map.Entry<Integer, com.github.steveice10.packetlib.packet.Packet> entry : packets.entrySet()) {
             int time = entry.getKey();
-            out.writeVarInt(time - lastTime);
+            len += writeVarInt(out, time - lastTime);
             lastTime = time;
 
-            writeToCache(out, entry.getValue());
+            len += writeToCache(out, entry.getValue());
         }
+        return len;
+    }
+
+    private static int writeVarInt(NetOutput out, int i) throws IOException {
+        int len = 1;
+        while ((i & -128) != 0) {
+            out.writeByte(i & 127 | 128);
+            i >>>= 7;
+            len++;
+        }
+        out.writeByte(i);
+        return len;
     }
 
     private static long coordToLong(int x, int z) {
@@ -704,7 +737,6 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
         List<com.github.steveice10.packetlib.packet.Packet> spawnPackets;
         List<com.github.steveice10.packetlib.packet.Packet> despawnPackets;
         int spawnTime;
-        int despawnTime = Integer.MAX_VALUE;
 
         private TrackedThing(List<com.github.steveice10.packetlib.packet.Packet> spawnPackets,
                              List<com.github.steveice10.packetlib.packet.Packet> despawnPackets) {
@@ -712,26 +744,41 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
             this.despawnPackets = despawnPackets;
         }
 
-        public void writeToCache(NetOutput out) throws IOException {
+        public int writeToCache(NetOutput indexOut, NetOutput cacheOut, int despawnTime, int index) throws IOException {
-            QuickReplaySender.writeToCache(out, spawnPackets);
+            indexOut.writeVarInt(spawnTime);
-            QuickReplaySender.writeToCache(out, despawnPackets);
+            indexOut.writeVarInt(despawnTime);
+            indexOut.writeVarInt(index);
+            index += QuickReplaySender.writeToCache(cacheOut, spawnPackets);
+            indexOut.writeVarInt(index);
+            index += QuickReplaySender.writeToCache(cacheOut, despawnPackets);
+            return index;
         }
     }
 
-    // For quicker jumping we store MC packets.
+    // For memory efficiency we store raw packets (we might even want to consider compression or memory mapped files).
-    // However, during replay analysis it's easier to use MCProtocolLib ones in part because MC packets have been
+    // During analysis we use TrackedThing which we then serialize (we'd have to do that anyway for caching)
-    // renamed from 1.8 to 1.9 but also because we cannot easily serialize them for caching.
+    // and afterwards deserialize in BakedTrackedThing as MC packets on demand for replaying.
-    // Therefore during analysis we use TrackedThing which we then serialize (we'd have to do that anyway for caching)
-    // and afterwards unserialize in BakedTrackedThing as MC packets for replaying.
     private static abstract class BakedTrackedThing {
-        List<Packet<?>> spawnPackets;
+        int indexSpawnPackets;
-        List<Packet<?>> despawnPackets;
+        int indexDespawnPackets;
         int spawnTime;
-        int despawnTime = Integer.MAX_VALUE;
+        int despawnTime;
 
-        private BakedTrackedThing(int version, NetInput in) throws IOException {
+        private BakedTrackedThing(NetInput in) throws IOException {
-            spawnPackets = readPacketsFromCache(version, in);
+            spawnTime = in.readVarInt();
-            despawnPackets = readPacketsFromCache(version, in);
+            despawnTime = in.readVarInt();
+            indexSpawnPackets = in.readVarInt();
+            indexDespawnPackets = in.readVarInt();
+        }
+
+        public void spawn(QuickReplaySender sender, Consumer<Packet<?>> send) {
+            sender.buf.readerIndex(indexSpawnPackets);
+            readPacketsFromCache(sender.bufInput).forEach(send);
+        }
+
+        public void despawn(QuickReplaySender sender, Consumer<Packet<?>> send) {
+            sender.buf.readerIndex(indexDespawnPackets);
+            readPacketsFromCache(sender.bufInput).forEach(send);
         }
 
         public abstract void play(int currentTimeStamp, int replayTime, Consumer<Packet<?>> send);
@@ -748,34 +795,53 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
         }
 
         @Override
-        public void writeToCache(NetOutput out) throws IOException {
+        public int writeToCache(NetOutput indexOut, NetOutput cacheOut, int despawnTime, int index) throws IOException {
-            super.writeToCache(out);
+            indexOut.writeByte(1);
+            index = super.writeToCache(indexOut, cacheOut, despawnTime, index);
 
-            out.writeVarInt(id);
+            indexOut.writeVarInt(id);
-            out.writeVarInt(locations.size());
+            indexOut.writeVarInt(index);
+            index += writeVarInt(cacheOut, locations.size());
             int lastTime = 0;
             for (Map.Entry<Integer, Location> entry : locations.entrySet()) {
                 int time = entry.getKey();
                 Location loc = entry.getValue();
-                out.writeVarInt(time - lastTime);
+                index += writeVarInt(cacheOut, time - lastTime);
                 lastTime = time;
-                out.writeDouble(loc.getX());
+                cacheOut.writeDouble(loc.getX());
-                out.writeDouble(loc.getY());
+                cacheOut.writeDouble(loc.getY());
-                out.writeDouble(loc.getZ());
+                cacheOut.writeDouble(loc.getZ());
-                out.writeFloat(loc.getYaw());
+                cacheOut.writeFloat(loc.getYaw());
-                out.writeFloat(loc.getPitch());
+                cacheOut.writeFloat(loc.getPitch());
+                index += 32;
             }
+
+            return index;
         }
     }
 
     private static class BakedEntity extends BakedTrackedThing {
         private int id;
-        private NavigableMap<Integer, Location> locations = new TreeMap<>();
+        private int index;
+        private NavigableMap<Integer, Location> locations;
 
-        private BakedEntity(int version, NetInput in) throws IOException {
+        private BakedEntity(NetInput in) throws IOException {
-            super(version, in);
+            super(in);
 
             id = in.readVarInt();
+            index = in.readVarInt();
+        }
+
+        @Override
+        @SneakyThrows(IOException.class)
+        public void spawn(QuickReplaySender sender, Consumer<Packet<?>> send) {
+            super.spawn(sender, send);
+
+            sender.buf.readerIndex(index);
+            NetInput in = sender.bufInput;
+
+            locations = new TreeMap<>();
+
             int time = 0;
             for (int i = in.readVarInt(); i > 0; i--) {
                 time += in.readVarInt();
@@ -783,6 +849,12 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
             }
         }
 
+        @Override
+        public void despawn(QuickReplaySender sender, Consumer<Packet<?>> send) {
+            super.despawn(sender, send);
+            locations = null;
+        }
+
         @Override
         public void play(int currentTimeStamp, int replayTime, Consumer<Packet<?>> send) {
             playMap(locations, currentTimeStamp, replayTime, l ->
@@ -806,38 +878,57 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
                     Collections.singletonList(new ServerUnloadChunkPacket(column.getX(), column.getZ())));
             com.github.steveice10.mc.protocol.data.game.chunk.Chunk[] chunks = column.getChunks();
             for (int i = 0; i < currentBlockState.length; i++) {
-                currentBlockState[i] = chunks[i] == null ? new BlockStorage() : chunks[i].getBlocks();
+                currentBlockState[i] = chunks[i] == null ? new BlockStorage() : copy(chunks[i].getBlocks());
             }
         }
 
         @Override
-        public void writeToCache(NetOutput out) throws IOException {
+        public int writeToCache(NetOutput indexOut, NetOutput cacheOut, int despawnTime, int index) throws IOException {
-            super.writeToCache(out);
+            indexOut.writeByte(2);
+            index = super.writeToCache(indexOut, cacheOut, despawnTime, index);
 
-            out.writeVarInt(blocksT.size());
+            indexOut.writeVarInt(index);
+            index += writeVarInt(cacheOut, blocksT.size());
             int lastTime = 0;
             for (Map.Entry<Integer, Collection<BlockChange>> entry : blocksT.entrySet()) {
                 int time = entry.getKey();
-                out.writeVarInt(time - lastTime);
+                index += writeVarInt(cacheOut, time - lastTime);
                 lastTime = time;
 
                 Collection<BlockChange> blockChanges = entry.getValue();
-                out.writeVarInt(blockChanges.size());
+                index += writeVarInt(cacheOut, blockChanges.size());
                 for (BlockChange blockChange : blockChanges) {
-                    NetUtil.writePosition(out, blockChange.pos);
+                    NetUtil.writePosition(cacheOut, blockChange.pos);
-                    NetUtil.writeBlockState(out, blockChange.from);
+                    index += 8;
-                    NetUtil.writeBlockState(out, blockChange.to);
+                    index += writeVarInt(cacheOut, blockChange.from.getId() << 4 | blockChange.from.getData() & 15);
+                    index += writeVarInt(cacheOut, blockChange.to.getId() << 4 | blockChange.to.getData() & 15);
                 }
             }
+
+            return index;
         }
     }
 
     private static class BakedChunk extends BakedTrackedThing {
-        private TreeMap<Integer, Collection<BlockChange>> blocksT = new TreeMap<>();
+        private int index;
-        private ListMultimap<Integer, BlockChange> blocks = Multimaps.newListMultimap(blocksT, LinkedList::new); // LinkedList to allow .descendingIterator
+        private TreeMap<Integer, Collection<BlockChange>> blocksT;
 
-        private BakedChunk(int version, NetInput in) throws IOException {
+        private BakedChunk(NetInput in) throws IOException {
-            super(version, in);
+            super(in);
+
+            index = in.readVarInt();
+        }
+
+        @Override
+        @SneakyThrows(IOException.class)
+        public void spawn(QuickReplaySender sender, Consumer<Packet<?>> send) {
+            super.spawn(sender, send);
+
+            sender.buf.readerIndex(index);
+            NetInput in = sender.bufInput;
+
+            blocksT = new TreeMap<>();
+            ListMultimap<Integer, BlockChange> blocks = Multimaps.newListMultimap(blocksT, LinkedList::new); // LinkedList to allow .descendingIterator
 
             int time = 0;
             for (int i = in.readVarInt(); i > 0; i--) {
@@ -853,6 +944,13 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
             }
         }
 
+        @Override
+        public void despawn(QuickReplaySender sender, Consumer<Packet<?>> send) {
+            super.despawn(sender, send);
+
+            blocksT = null;
+        }
+
         @Override
         public void play(int currentTimeStamp, int replayTime, Consumer<Packet<?>> send) {
             blocksT.subMap(currentTimeStamp, false, replayTime, true).values()
@@ -895,20 +993,44 @@ public class QuickReplaySender extends ChannelHandlerAdapter implements ReplaySe
         }
 
         @Override
-        public void writeToCache(NetOutput out) throws IOException {
+        public int writeToCache(NetOutput indexOut, NetOutput cacheOut, int despawnTime, int index) throws IOException {
-            super.writeToCache(out);
+            indexOut.writeByte(3);
+            index = super.writeToCache(indexOut, cacheOut, despawnTime, index);
 
-            QuickReplaySender.writeToCache(out, rainStrengths);
+            indexOut.writeVarInt(index);
+            index += QuickReplaySender.writeToCache(cacheOut, rainStrengths);
+
+            return index;
         }
     }
 
     private static class BakedWeather extends BakedTrackedThing {
-        private TreeMap<Integer, Packet<?>> rainStrengths = new TreeMap<>();
+        private int index;
+        private TreeMap<Integer, Packet<?>> rainStrengths;
 
-        private BakedWeather(int version, NetInput in) throws IOException {
+        private BakedWeather(NetInput in) throws IOException {
-            super(version, in);
+            super(in);
 
-            readFromCache(version, in, rainStrengths);
+            index = in.readVarInt();
+        }
+
+        @Override
+        @SneakyThrows(IOException.class)
+        public void spawn(QuickReplaySender sender, Consumer<Packet<?>> send) {
+            super.spawn(sender, send);
+
+            sender.buf.readerIndex(index);
+
+            rainStrengths = new TreeMap<>();
+
+            readFromCache(sender.bufInput, rainStrengths);
+        }
+
+        @Override
+        public void despawn(QuickReplaySender sender, Consumer<Packet<?>> send) {
+            super.despawn(sender, send);
+
+            rainStrengths = null;
         }
 
         @Override