Merge branch 'mc-1.14.x' into mc-1.15.x

src/main/java/dan200/computercraft/ComputerCraft.java

@@ -7,7 +7,6 @@ package dan200.computercraft;
 
 import dan200.computercraft.api.turtle.event.TurtleAction;
 import dan200.computercraft.core.apis.http.AddressRule;
-import dan200.computercraft.core.apis.http.websocket.Websocket;
 import dan200.computercraft.shared.Config;
 import dan200.computercraft.shared.computer.blocks.BlockComputer;
 import dan200.computercraft.shared.computer.core.ClientComputerRegistry;
@@ -22,6 +21,7 @@ import dan200.computercraft.shared.peripheral.modem.wired.BlockWiredModemFull;
 import dan200.computercraft.shared.peripheral.modem.wired.ItemBlockCable;
 import dan200.computercraft.shared.peripheral.modem.wireless.BlockWirelessModem;
 import dan200.computercraft.shared.peripheral.monitor.BlockMonitor;
+import dan200.computercraft.shared.peripheral.monitor.MonitorRenderer;
 import dan200.computercraft.shared.peripheral.printer.BlockPrinter;
 import dan200.computercraft.shared.peripheral.speaker.BlockSpeaker;
 import dan200.computercraft.shared.pocket.items.ItemPocketComputer;
@@ -88,7 +88,7 @@ public final class ComputerCraft
     public static long httpMaxDownload = 16 * 1024 * 1024;
     public static long httpMaxUpload = 4 * 1024 * 1024;
     public static int httpMaxWebsockets = 4;
-    public static int httpMaxWebsocketMessage = Websocket.MAX_MESSAGE_SIZE;
+    public static int httpMaxWebsocketMessage = 128 * 1024;
 
     public static boolean enableCommandBlock = false;
     public static int modem_range = 64;
@@ -96,6 +96,7 @@ public final class ComputerCraft
     public static int modem_rangeDuringStorm = 64;
     public static int modem_highAltitudeRangeDuringStorm = 384;
     public static int maxNotesPerTick = 8;
+    public static MonitorRenderer monitorRenderer = MonitorRenderer.BEST;
 
     public static boolean turtlesNeedFuel = true;
     public static int turtleFuelLimit = 20000;

src/main/java/dan200/computercraft/api/filesystem/FileAttributes.java

@@ -0,0 +1,81 @@
+/*
+ * This file is part of the public ComputerCraft API - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2020. This API may be redistributed unmodified and in full only.
+ * For help using the API, and posting your mods, visit the forums at computercraft.info.
+ */
+package dan200.computercraft.api.filesystem;
+
+import java.nio.file.attribute.BasicFileAttributes;
+import java.nio.file.attribute.FileTime;
+import java.time.Instant;
+
+/**
+ * A simple version of {@link BasicFileAttributes}, which provides what information a {@link IMount} already exposes.
+ */
+final class FileAttributes implements BasicFileAttributes
+{
+    private static final FileTime EPOCH = FileTime.from( Instant.EPOCH );
+
+    private final boolean isDirectory;
+    private final long size;
+
+    FileAttributes( boolean isDirectory, long size )
+    {
+        this.isDirectory = isDirectory;
+        this.size = size;
+    }
+
+    @Override
+    public FileTime lastModifiedTime()
+    {
+        return EPOCH;
+    }
+
+    @Override
+    public FileTime lastAccessTime()
+    {
+        return EPOCH;
+    }
+
+    @Override
+    public FileTime creationTime()
+    {
+        return EPOCH;
+    }
+
+    @Override
+    public boolean isRegularFile()
+    {
+        return !isDirectory;
+    }
+
+    @Override
+    public boolean isDirectory()
+    {
+        return isDirectory;
+    }
+
+    @Override
+    public boolean isSymbolicLink()
+    {
+        return false;
+    }
+
+    @Override
+    public boolean isOther()
+    {
+        return false;
+    }
+
+    @Override
+    public long size()
+    {
+        return size;
+    }
+
+    @Override
+    public Object fileKey()
+    {
+        return null;
+    }
+}

src/main/java/dan200/computercraft/api/filesystem/FileOperationException.java

@@ -27,7 +27,7 @@ public class FileOperationException extends IOException
         this.filename = filename;
     }
 
-    public FileOperationException( String message )
+    public FileOperationException( @Nonnull String message )
     {
         super( Objects.requireNonNull( message, "message cannot be null" ) );
         this.filename = null;

src/main/java/dan200/computercraft/api/filesystem/IMount.java

@@ -12,6 +12,7 @@ import net.minecraft.world.World;
 import javax.annotation.Nonnull;
 import java.io.IOException;
 import java.nio.channels.ReadableByteChannel;
+import java.nio.file.attribute.BasicFileAttributes;
 import java.util.List;
 
 /**
@@ -76,4 +77,18 @@ public interface IMount
      */
     @Nonnull
     ReadableByteChannel openForRead( @Nonnull String path ) throws IOException;
+
+    /**
+     * Get attributes about the given file.
+     *
+     * @param path The path to query.
+     * @return File attributes for the given file.
+     * @throws IOException If the file does not exist, or attributes could not be fetched.
+     */
+    @Nonnull
+    default BasicFileAttributes getAttributes( @Nonnull String path ) throws IOException
+    {
+        if( !exists( path ) ) throw new FileOperationException( path, "No such file" );
+        return new FileAttributes( isDirectory( path ), getSize( path ) );
+    }
 }

src/main/java/dan200/computercraft/api/filesystem/IWritableMount.java

@@ -13,6 +13,7 @@ import javax.annotation.Nonnull;
 import java.io.IOException;
 import java.io.OutputStream;
 import java.nio.channels.WritableByteChannel;
+import java.util.OptionalLong;
 
 /**
  * Represents a part of a virtual filesystem that can be mounted onto a computer using {@link IComputerAccess#mount(String, IMount)}
@@ -74,4 +75,16 @@ public interface IWritableMount extends IMount
      * @throws IOException If the remaining space could not be computed.
      */
     long getRemainingSpace() throws IOException;
+
+    /**
+     * Get the capacity of this mount. This should be equal to the size of all files/directories on this mount, minus
+     * the {@link #getRemainingSpace()}.
+     *
+     * @return The capacity of this mount, in bytes.
+     */
+    @Nonnull
+    default OptionalLong getCapacity()
+    {
+        return OptionalLong.empty();
+    }
 }

src/main/java/dan200/computercraft/client/gui/FixedWidthFontRenderer.java

@@ -46,8 +46,17 @@ public final class FixedWidthFontRenderer
         return (float) ((rgb[0] + rgb[1] + rgb[2]) / 3);
     }
 
+    private static int getColour( char c )
+    {
+        int i = "0123456789abcdef".indexOf( c );
+        return i < 0 ? 0 : 15 - i;
+    }
+
     private static void drawChar( Matrix4f transform, IVertexBuilder buffer, float x, float y, int index, float r, float g, float b )
     {
+        // Short circuit to avoid the common case - the texture should be blank here after all.
+        if( index == '\0' || index == ' ' ) return;
+
         int column = index % 16;
         int row = index / 16;
 
@@ -72,6 +81,24 @@ public final class FixedWidthFontRenderer
         buffer.pos( transform, x + width, y + height, 0 ).color( r, g, b, 1.0f ).tex( BACKGROUND_END, BACKGROUND_END ).endVertex();
     }
 
+    private static void drawQuad( Matrix4f transform, IVertexBuilder buffer, float x, float y, float width, float height, Palette palette, boolean greyscale, char colourIndex )
+    {
+        double[] colour = palette.getColour( getColour( colourIndex ) );
+        float r, g, b;
+        if( greyscale )
+        {
+            r = g = b = toGreyscale( colour );
+        }
+        else
+        {
+            r = (float) colour[0];
+            g = (float) colour[1];
+            b = (float) colour[2];
+        }
+
+        drawQuad( transform, buffer, x, y, width, height, r, g, b );
+    }
+
     private static void drawBackground(
         @Nonnull Matrix4f transform, @Nonnull IVertexBuilder renderer, float x, float y,
         @Nonnull TextBuffer backgroundColour, @Nonnull Palette palette, boolean greyscale,
@@ -80,56 +107,34 @@ public final class FixedWidthFontRenderer
     {
         if( leftMarginSize > 0 )
         {
-            double[] colour = palette.getColour( 15 - "0123456789abcdef".indexOf( backgroundColour.charAt( 0 ) ) );
-            float r, g, b;
-            if( greyscale )
-            {
-                r = g = b = toGreyscale( colour );
-            }
-            else
-            {
-                r = (float) colour[0];
-                g = (float) colour[1];
-                b = (float) colour[2];
-            }
-
-            drawQuad( transform, renderer, x - leftMarginSize, y, leftMarginSize, height, r, g, b );
+            drawQuad( transform, renderer, x - leftMarginSize, y, leftMarginSize, height, palette, greyscale, backgroundColour.charAt( 0 ) );
         }
 
         if( rightMarginSize > 0 )
         {
-            double[] colour = palette.getColour( 15 - "0123456789abcdef".indexOf( backgroundColour.charAt( backgroundColour.length() - 1 ) ) );
-            float r, g, b;
-            if( greyscale )
-            {
-                r = g = b = toGreyscale( colour );
-            }
-            else
-            {
-                r = (float) colour[0];
-                g = (float) colour[1];
-                b = (float) colour[2];
-            }
-
-            drawQuad( transform, renderer, x + backgroundColour.length() * FONT_WIDTH, y, rightMarginSize, height, r, g, b );
+            drawQuad( transform, renderer, x + backgroundColour.length() * FONT_WIDTH, y, rightMarginSize, height, palette, greyscale, backgroundColour.charAt( backgroundColour.length() - 1 ) );
         }
 
+        // Batch together runs of identical background cells.
+        int blockStart = 0;
+        char blockColour = '\0';
         for( int i = 0; i < backgroundColour.length(); i++ )
         {
-            double[] colour = palette.getColour( 15 - "0123456789abcdef".indexOf( backgroundColour.charAt( i ) ) );
-            float r, g, b;
-            if( greyscale )
+            char colourIndex = backgroundColour.charAt( i );
+            if( colourIndex == blockColour ) continue;
+
+            if( blockColour != '\0' )
             {
-                r = g = b = toGreyscale( colour );
-            }
-            else
-            {
-                r = (float) colour[0];
-                g = (float) colour[1];
-                b = (float) colour[2];
+                drawQuad( transform, renderer, x + blockStart * FONT_WIDTH, y, FONT_WIDTH * (i - blockStart), height, palette, greyscale, blockColour );
             }
 
-            drawQuad( transform, renderer, x + i * FONT_WIDTH, y, FONT_WIDTH, height, r, g, b );
+            blockColour = colourIndex;
+            blockStart = i;
+        }
+
+        if( blockColour != '\0' )
+        {
+            drawQuad( transform, renderer, x + blockStart * FONT_WIDTH, y, FONT_WIDTH * (backgroundColour.length() - blockStart), height, palette, greyscale, blockColour );
         }
     }
 
@@ -172,8 +177,7 @@ public final class FixedWidthFontRenderer
         @Nonnull Palette palette, boolean greyscale, float leftMarginSize, float rightMarginSize
     )
     {
-        Minecraft.getInstance().getTextureManager().bindTexture( FONT );
-        // TODO: RenderSystem.texParameter( GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_WRAP_S, GL11.GL_CLAMP );
+        bindFont();
 
         IRenderTypeBuffer.Impl renderer = Minecraft.getInstance().getRenderTypeBuffers().getBufferSource();
         drawString( IDENTITY, ((IRenderTypeBuffer) renderer).getBuffer( TYPE ), x, y, text, textColour, backgroundColour, palette, greyscale, leftMarginSize, rightMarginSize );
@@ -258,9 +262,7 @@ public final class FixedWidthFontRenderer
         float topMarginSize, float bottomMarginSize, float leftMarginSize, float rightMarginSize
     )
     {
-        Minecraft.getInstance().getTextureManager().bindTexture( FONT );
-        // TODO: Is this the most sane thing?
-        RenderSystem.texParameter( GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_WRAP_S, GL11.GL_CLAMP );
+        bindFont();
 
         IRenderTypeBuffer.Impl renderer = Minecraft.getInstance().getRenderTypeBuffers().getBufferSource();
         IVertexBuilder buffer = renderer.getBuffer( TYPE );
@@ -284,8 +286,7 @@ public final class FixedWidthFontRenderer
 
     public static void drawEmptyTerminal( @Nonnull Matrix4f transform, float x, float y, float width, float height )
     {
-        Minecraft.getInstance().getTextureManager().bindTexture( FONT );
-        RenderSystem.texParameter( GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_WRAP_S, GL11.GL_CLAMP );
+        bindFont();
 
         IRenderTypeBuffer.Impl renderer = Minecraft.getInstance().getRenderTypeBuffers().getBufferSource();
         drawEmptyTerminal( transform, renderer, x, y, width, height );
@@ -303,6 +304,12 @@ public final class FixedWidthFontRenderer
         drawQuad( transform, renderer.getBuffer( Type.BLOCKER ), x, y, width, height, colour.getR(), colour.getG(), colour.getB() );
     }
 
+    private static void bindFont()
+    {
+        Minecraft.getInstance().getTextureManager().bindTexture( FONT );
+        RenderSystem.texParameter( GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_WRAP_S, GL11.GL_CLAMP );
+    }
+
     private static final class Type extends RenderState
     {
         private static final int GL_MODE = GL11.GL_TRIANGLES;

src/main/java/dan200/computercraft/client/proxy/ComputerCraftProxyClient.java

@@ -9,6 +9,7 @@ import dan200.computercraft.ComputerCraft;
 import dan200.computercraft.client.gui.*;
 import dan200.computercraft.client.render.TileEntityMonitorRenderer;
 import dan200.computercraft.client.render.TileEntityTurtleRenderer;
+import dan200.computercraft.client.render.TurtlePlayerRenderer;
 import dan200.computercraft.shared.common.ContainerHeldItem;
 import dan200.computercraft.shared.computer.inventory.ContainerComputer;
 import dan200.computercraft.shared.computer.inventory.ContainerViewComputer;
@@ -18,6 +19,7 @@ import dan200.computercraft.shared.peripheral.monitor.TileMonitor;
 import dan200.computercraft.shared.peripheral.printer.ContainerPrinter;
 import dan200.computercraft.shared.pocket.inventory.ContainerPocketComputer;
 import dan200.computercraft.shared.turtle.blocks.TileTurtle;
+import dan200.computercraft.shared.turtle.core.TurtlePlayer;
 import dan200.computercraft.shared.turtle.inventory.ContainerTurtle;
 import net.minecraft.client.gui.ScreenManager;
 import net.minecraft.client.renderer.RenderType;
@@ -26,6 +28,7 @@ import net.minecraftforge.api.distmarker.Dist;
 import net.minecraftforge.event.world.WorldEvent;
 import net.minecraftforge.eventbus.api.SubscribeEvent;
 import net.minecraftforge.fml.client.registry.ClientRegistry;
+import net.minecraftforge.fml.client.registry.RenderingRegistry;
 import net.minecraftforge.fml.common.Mod;
 import net.minecraftforge.fml.event.lifecycle.FMLClientSetupEvent;
 
@@ -51,6 +54,8 @@ public final class ComputerCraftProxyClient
         ClientRegistry.bindTileEntityRenderer( TileTurtle.FACTORY_NORMAL, TileEntityTurtleRenderer::new );
         ClientRegistry.bindTileEntityRenderer( TileTurtle.FACTORY_ADVANCED, TileEntityTurtleRenderer::new );
         // TODO: ClientRegistry.bindTileEntityRenderer( TileCable.FACTORY, x -> new TileEntityCableRenderer() );
+
+        RenderingRegistry.registerEntityRenderingHandler( TurtlePlayer.TYPE, TurtlePlayerRenderer::new );
     }
 
     private static void registerContainers()

src/main/java/dan200/computercraft/client/render/TileEntityMonitorRenderer.java

@@ -11,6 +11,7 @@ import dan200.computercraft.client.FrameInfo;
 import dan200.computercraft.client.gui.FixedWidthFontRenderer;
 import dan200.computercraft.core.terminal.Terminal;
 import dan200.computercraft.shared.peripheral.monitor.ClientMonitor;
+import dan200.computercraft.shared.peripheral.monitor.MonitorRenderer;
 import dan200.computercraft.shared.peripheral.monitor.TileMonitor;
 import dan200.computercraft.shared.util.DirectionUtil;
 import net.minecraft.client.renderer.*;
@@ -92,7 +93,7 @@ public class TileEntityMonitorRenderer extends TileEntityRenderer<TileMonitor>
             boolean redraw = originTerminal.pollTerminalChanged();
             if( originTerminal.buffer == null )
             {
-                originTerminal.createBuffer();
+                originTerminal.createBuffer( MonitorRenderer.VBO );
                 redraw = true;
             }
             VertexBuffer vbo = originTerminal.buffer;

src/main/java/dan200/computercraft/client/render/TurtlePlayerRenderer.java

@@ -0,0 +1,37 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2020. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.client.render;
+
+import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.shared.turtle.core.TurtlePlayer;
+import net.minecraft.client.renderer.entity.EntityRenderer;
+import net.minecraft.client.renderer.entity.EntityRendererManager;
+import net.minecraft.util.ResourceLocation;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
+public class TurtlePlayerRenderer extends EntityRenderer<TurtlePlayer>
+{
+    public TurtlePlayerRenderer( EntityRendererManager renderManager )
+    {
+        super( renderManager );
+    }
+
+    @Override
+    public void doRender( @Nonnull TurtlePlayer entity, double x, double y, double z, float entityYaw, float partialTicks )
+    {
+        ComputerCraft.log.error( "Rendering TurtlePlayer on the client side, at {}", entity.getPosition() );
+    }
+
+    @Nullable
+    @Override
+    protected ResourceLocation getEntityTexture( @Nonnull TurtlePlayer entity )
+    {
+        return null;
+    }
+}

src/main/java/dan200/computercraft/core/apis/FSAPI.java

@@ -22,6 +22,11 @@ import java.io.BufferedReader;
 import java.io.BufferedWriter;
 import java.nio.channels.ReadableByteChannel;
 import java.nio.channels.WritableByteChannel;
+import java.nio.file.attribute.BasicFileAttributes;
+import java.nio.file.attribute.FileTime;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.OptionalLong;
 import java.util.function.Function;
 
 import static dan200.computercraft.api.lua.ArgumentHelper.getString;
@@ -76,6 +81,8 @@ public class FSAPI implements ILuaAPI
             "getFreeSpace",
             "find",
             "getDir",
+            "getCapacity",
+            "attributes",
         };
     }
 
@@ -315,9 +322,8 @@ public class FSAPI implements ILuaAPI
                     throw new LuaException( e.getMessage() );
                 }
             }
-            case 14:
+            case 14: // find
             {
-                // find
                 String path = getString( args, 0 );
                 try
                 {
@@ -329,15 +335,50 @@ public class FSAPI implements ILuaAPI
                     throw new LuaException( e.getMessage() );
                 }
             }
-            case 15:
+            case 15: // getDir
             {
-                // getDir
                 String path = getString( args, 0 );
                 return new Object[] { FileSystem.getDirectory( path ) };
             }
+            case 16: // getCapacity
+            {
+                String path = getString( args, 0 );
+                try
+                {
+                    OptionalLong capacity = m_fileSystem.getCapacity( path );
+                    return new Object[] { capacity.isPresent() ? capacity.getAsLong() : null };
+                }
+                catch( FileSystemException e )
+                {
+                    throw new LuaException( e.getMessage() );
+                }
+            }
+            case 17: // attributes
+            {
+                String path = getString( args, 0 );
+                try
+                {
+                    BasicFileAttributes attributes = m_fileSystem.getAttributes( path );
+                    Map<String, Object> result = new HashMap<>();
+                    result.put( "modification", getFileTime( attributes.lastModifiedTime() ) );
+                    result.put( "created", getFileTime( attributes.creationTime() ) );
+                    result.put( "size", attributes.isDirectory() ? 0 : attributes.size() );
+                    result.put( "isDir", attributes.isDirectory() );
+                    return new Object[] { result };
+                }
+                catch( FileSystemException e )
+                {
+                    throw new LuaException( e.getMessage() );
+                }
+            }
             default:
                 assert false;
                 return null;
         }
     }
+
+    private static long getFileTime( FileTime time )
+    {
+        return time == null ? 0 : time.toMillis();
+    }
 }

src/main/java/dan200/computercraft/core/apis/FastLuaException.java

@@ -0,0 +1,35 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2020. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.core.apis;
+
+import dan200.computercraft.api.lua.LuaException;
+
+import javax.annotation.Nullable;
+
+/**
+ * A Lua exception which does not contain its stack trace.
+ */
+public class FastLuaException extends LuaException
+{
+    private static final long serialVersionUID = 5957864899303561143L;
+
+    public FastLuaException( @Nullable String message )
+    {
+        super( message );
+    }
+
+    public FastLuaException( @Nullable String message, int level )
+    {
+        super( message, level );
+    }
+
+    @Override
+    public synchronized Throwable fillInStackTrace()
+    {
+        return this;
+    }
+}

src/main/java/dan200/computercraft/core/apis/IAPIEnvironment.java

@@ -18,6 +18,8 @@ import javax.annotation.Nullable;
 
 public interface IAPIEnvironment
 {
+    String TIMER_EVENT = "timer";
+
     @FunctionalInterface
     interface IPeripheralChangeListener
     {
@@ -64,6 +66,10 @@ public interface IAPIEnvironment
 
     void setLabel( @Nullable String label );
 
+    int startTimer( long ticks );
+
+    void cancelTimer( int id );
+
     void addTrackingChange( @Nonnull TrackingField field, long change );
 
     default void addTrackingChange( @Nonnull TrackingField field )

src/main/java/dan200/computercraft/core/apis/OSAPI.java

@@ -9,6 +9,8 @@ import dan200.computercraft.api.lua.ILuaAPI;
 import dan200.computercraft.api.lua.ILuaContext;
 import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.shared.util.StringUtil;
+import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
+import it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap;
 
 import javax.annotation.Nonnull;
 import java.time.Instant;
@@ -24,24 +26,12 @@ public class OSAPI implements ILuaAPI
 {
     private IAPIEnvironment m_apiEnvironment;
 
-    private final Map<Integer, Timer> m_timers;
-    private final Map<Integer, Alarm> m_alarms;
+    private final Int2ObjectMap<Alarm> m_alarms = new Int2ObjectOpenHashMap<>();
     private int m_clock;
     private double m_time;
     private int m_day;
 
-    private int m_nextTimerToken;
-    private int m_nextAlarmToken;
-
-    private static class Timer
-    {
-        int m_ticksLeft;
-
-        Timer( int ticksLeft )
-        {
-            m_ticksLeft = ticksLeft;
-        }
-    }
+    private int m_nextAlarmToken = 0;
 
     private static class Alarm implements Comparable<Alarm>
     {
@@ -66,10 +56,6 @@ public class OSAPI implements ILuaAPI
     public OSAPI( IAPIEnvironment environment )
     {
         m_apiEnvironment = environment;
-        m_nextTimerToken = 0;
-        m_nextAlarmToken = 0;
-        m_timers = new HashMap<>();
-        m_alarms = new HashMap<>();
     }
 
     // ILuaAPI implementation
@@ -87,11 +73,6 @@ public class OSAPI implements ILuaAPI
         m_day = m_apiEnvironment.getComputerEnvironment().getDay();
         m_clock = 0;
 
-        synchronized( m_timers )
-        {
-            m_timers.clear();
-        }
-
         synchronized( m_alarms )
         {
             m_alarms.clear();
@@ -101,26 +82,7 @@ public class OSAPI implements ILuaAPI
     @Override
     public void update()
     {
-        synchronized( m_timers )
-        {
-            // Update the clock
-            m_clock++;
-
-            // Countdown all of our active timers
-            Iterator<Map.Entry<Integer, Timer>> it = m_timers.entrySet().iterator();
-            while( it.hasNext() )
-            {
-                Map.Entry<Integer, Timer> entry = it.next();
-                Timer timer = entry.getValue();
-                timer.m_ticksLeft--;
-                if( timer.m_ticksLeft <= 0 )
-                {
-                    // Queue the "timer" event
-                    queueLuaEvent( "timer", new Object[] { entry.getKey() } );
-                    it.remove();
-                }
-            }
-        }
+        m_clock++;
 
         // Wait for all of our alarms
         synchronized( m_alarms )
@@ -133,10 +95,10 @@ public class OSAPI implements ILuaAPI
             if( time > previousTime || day > previousDay )
             {
                 double now = m_day * 24.0 + m_time;
-                Iterator<Map.Entry<Integer, Alarm>> it = m_alarms.entrySet().iterator();
+                Iterator<Int2ObjectMap.Entry<Alarm>> it = m_alarms.int2ObjectEntrySet().iterator();
                 while( it.hasNext() )
                 {
-                    Map.Entry<Integer, Alarm> entry = it.next();
+                    Int2ObjectMap.Entry<Alarm> entry = it.next();
                     Alarm alarm = entry.getValue();
                     double t = alarm.m_day * 24.0 + alarm.m_time;
                     if( now >= t )
@@ -155,11 +117,6 @@ public class OSAPI implements ILuaAPI
     @Override
     public void shutdown()
     {
-        synchronized( m_timers )
-        {
-            m_timers.clear();
-        }
-
         synchronized( m_alarms )
         {
             m_alarms.clear();
@@ -229,11 +186,8 @@ public class OSAPI implements ILuaAPI
             {
                 // startTimer
                 double timer = getFiniteDouble( args, 0 );
-                synchronized( m_timers )
-                {
-                    m_timers.put( m_nextTimerToken, new Timer( (int) Math.round( timer / 0.05 ) ) );
-                    return new Object[] { m_nextTimerToken++ };
-                }
+                int id = m_apiEnvironment.startTimer( Math.round( timer / 0.05 ) );
+                return new Object[] { id };
             }
             case 2:
             {
@@ -278,10 +232,7 @@ public class OSAPI implements ILuaAPI
                 return null;
             }
             case 10: // clock
-                synchronized( m_timers )
-                {
-                    return new Object[] { m_clock * 0.05 };
-                }
+                return new Object[] { m_clock * 0.05 };
             case 11:
             {
                 // time
@@ -345,10 +296,7 @@ public class OSAPI implements ILuaAPI
             {
                 // cancelTimer
                 int token = getInt( args, 0 );
-                synchronized( m_timers )
-                {
-                    m_timers.remove( token );
-                }
+                m_apiEnvironment.cancelTimer( token );
                 return null;
             }
             case 14:

src/main/java/dan200/computercraft/core/apis/PeripheralAPI.java

@@ -366,22 +366,30 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
                 String methodName = getString( args, 1 );
                 Object[] methodArgs = Arrays.copyOfRange( args, 2, args.length );
 
-                if( side != null )
+                if( side == null ) throw new LuaException( "No peripheral attached" );
+
+                PeripheralWrapper p;
+                synchronized( m_peripherals )
                 {
-                    PeripheralWrapper p;
-                    synchronized( m_peripherals )
-                    {
-                        p = m_peripherals[side.ordinal()];
-                    }
-                    if( p != null )
-                    {
-                        return p.call( context, methodName, methodArgs );
-                    }
+                    p = m_peripherals[side.ordinal()];
+                }
+                if( p == null ) throw new LuaException( "No peripheral attached" );
+
+                try
+                {
+                    return p.call( context, methodName, methodArgs );
+                }
+                catch( LuaException e )
+                {
+                    // We increase the error level by one in order to shift the error level to where peripheral.call was
+                    // invoked. It would be possible to do it in Lua code, but would add significantly more overhead.
+                    if( e.getLevel() > 0 ) throw new FastLuaException( e.getMessage(), e.getLevel() + 1 );
+                    throw e;
                 }
-                throw new LuaException( "No peripheral attached" );
             }
             default:
                 return null;
         }
     }
+
 }

src/main/java/dan200/computercraft/core/apis/http/websocket/Websocket.java

@@ -40,7 +40,11 @@ import java.util.concurrent.Future;
  */
 public class Websocket extends Resource<Websocket>
 {
-    public static final int MAX_MESSAGE_SIZE = 64 * 1024;
+    /**
+     * We declare the maximum size to be 2^30 bytes. While messages can be much longer, we set an arbitrary limit as
+     * working with larger messages (especially within a Lua VM) is absurd.
+     */
+    public static final int MAX_MESSAGE_SIZE = 1 << 30;
 
     static final String SUCCESS_EVENT = "websocket_success";
     static final String FAILURE_EVENT = "websocket_failure";

src/main/java/dan200/computercraft/core/apis/http/websocket/WebsocketHandle.java

@@ -7,6 +7,7 @@ package dan200.computercraft.core.apis.http.websocket;
 
 import com.google.common.base.Objects;
 import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.api.lua.ArgumentHelper;
 import dan200.computercraft.api.lua.ILuaContext;
 import dan200.computercraft.api.lua.ILuaObject;
 import dan200.computercraft.api.lua.LuaException;
@@ -23,6 +24,7 @@ import java.io.Closeable;
 import java.util.Arrays;
 
 import static dan200.computercraft.api.lua.ArgumentHelper.optBoolean;
+import static dan200.computercraft.core.apis.IAPIEnvironment.TIMER_EVENT;
 import static dan200.computercraft.core.apis.http.websocket.Websocket.CLOSE_EVENT;
 import static dan200.computercraft.core.apis.http.websocket.Websocket.MESSAGE_EVENT;
 
@@ -53,7 +55,21 @@ public class WebsocketHandle implements ILuaObject, Closeable
         switch( method )
         {
             case 0: // receive
+            {
                 checkOpen();
+                int timeoutId;
+                if( arguments.length <= 0 || arguments[0] == null )
+                {
+                    // We do this rather odd argument validation to ensure we can tell the difference between a
+                    // negative timeout and an absent one.
+                    timeoutId = -1;
+                }
+                else
+                {
+                    double timeout = ArgumentHelper.getFiniteDouble( arguments, 0 );
+                    timeoutId = websocket.environment().startTimer( Math.round( timeout / 0.05 ) );
+                }
+
                 while( true )
                 {
                     Object[] event = context.pullEvent( null );
@@ -63,9 +79,17 @@ public class WebsocketHandle implements ILuaObject, Closeable
                     }
                     else if( event.length >= 2 && Objects.equal( event[0], CLOSE_EVENT ) && Objects.equal( event[1], websocket.address() ) && closed )
                     {
+                        // If the socket is closed abort.
+                        return null;
+                    }
+                    else if( event.length >= 2 && timeoutId != -1 && Objects.equal( event[0], TIMER_EVENT )
+                        && event[1] instanceof Number && ((Number) event[1]).intValue() == timeoutId )
+                    {
+                        // If we received a matching timer event then abort.
                         return null;
                     }
                 }
+            }
 
             case 1: // send
             {

src/main/java/dan200/computercraft/core/computer/Computer.java

@@ -181,7 +181,7 @@ public class Computer
         executor.tick();
 
         // Update the environment's internal state.
-        internalEnvironment.update();
+        internalEnvironment.tick();
 
         // Propagate the environment's output to the world.
         if( internalEnvironment.updateOutput() ) externalOutputChanged.set( true );

src/main/java/dan200/computercraft/core/computer/ComputerExecutor.java

@@ -426,6 +426,7 @@ final class ComputerExecutor
             }
 
             // Init APIs
+            computer.getEnvironment().reset();
             for( ILuaAPI api : apis ) api.startup();
 
             // Init lua
@@ -469,6 +470,7 @@ final class ComputerExecutor
 
             // Shutdown our APIs
             for( ILuaAPI api : apis ) api.shutdown();
+            computer.getEnvironment().reset();
 
             // Unload filesystem
             if( fileSystem != null )

src/main/java/dan200/computercraft/core/computer/Environment.java

@@ -5,6 +5,7 @@
  */
 package dan200.computercraft.core.computer;
 
+import dan200.computercraft.api.lua.ILuaAPI;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.api.peripheral.IWorkMonitor;
 import dan200.computercraft.core.apis.IAPIEnvironment;
@@ -12,9 +13,12 @@ import dan200.computercraft.core.filesystem.FileSystem;
 import dan200.computercraft.core.terminal.Terminal;
 import dan200.computercraft.core.tracking.Tracking;
 import dan200.computercraft.core.tracking.TrackingField;
+import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
+import it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap;
 
 import javax.annotation.Nonnull;
 import java.util.Arrays;
+import java.util.Iterator;
 
 /**
  * Represents the "environment" that a {@link Computer} exists in.
@@ -53,6 +57,9 @@ public final class Environment implements IAPIEnvironment
     private final IPeripheral[] peripherals = new IPeripheral[ComputerSide.COUNT];
     private IPeripheralChangeListener peripheralListener = null;
 
+    private final Int2ObjectMap<Timer> timers = new Int2ObjectOpenHashMap<>();
+    private int nextTimerToken = 0;
+
     Environment( Computer computer )
     {
         this.computer = computer;
@@ -198,17 +205,47 @@ public final class Environment implements IAPIEnvironment
     }
 
     /**
-     * Called on the main thread to update the internal state of the computer.
+     * Called when the computer starts up or shuts down, to reset any internal state.
      *
-     * This just queues a {@code redstone} event if the input has changed.
+     * @see ILuaAPI#startup()
+     * @see ILuaAPI#shutdown()
      */
-    void update()
+    void reset()
+    {
+        synchronized( timers )
+        {
+            timers.clear();
+        }
+    }
+
+    /**
+     * Called on the main thread to update the internal state of the computer.
+     */
+    void tick()
     {
         if( inputChanged )
         {
             inputChanged = false;
             queueEvent( "redstone", null );
         }
+
+        synchronized( timers )
+        {
+            // Countdown all of our active timers
+            Iterator<Int2ObjectMap.Entry<Timer>> it = timers.int2ObjectEntrySet().iterator();
+            while( it.hasNext() )
+            {
+                Int2ObjectMap.Entry<Timer> entry = it.next();
+                Timer timer = entry.getValue();
+                timer.ticksLeft--;
+                if( timer.ticksLeft <= 0 )
+                {
+                    // Queue the "timer" event
+                    queueEvent( TIMER_EVENT, new Object[] { entry.getIntKey() } );
+                    it.remove();
+                }
+            }
+        }
     }
 
     /**
@@ -303,9 +340,38 @@ public final class Environment implements IAPIEnvironment
         computer.setLabel( label );
     }
 
+    @Override
+    public int startTimer( long ticks )
+    {
+        synchronized( timers )
+        {
+            timers.put( nextTimerToken, new Timer( ticks ) );
+            return nextTimerToken++;
+        }
+    }
+
+    @Override
+    public void cancelTimer( int id )
+    {
+        synchronized( timers )
+        {
+            timers.remove( id );
+        }
+    }
+
     @Override
     public void addTrackingChange( @Nonnull TrackingField field, long change )
     {
         Tracking.addValue( computer, field, change );
     }
+
+    private static class Timer
+    {
+        long ticksLeft;
+
+        Timer( long ticksLeft )
+        {
+            this.ticksLeft = ticksLeft;
+        }
+    }
 }

src/main/java/dan200/computercraft/core/filesystem/ComboMount.java

@@ -11,6 +11,7 @@ import dan200.computercraft.api.filesystem.IMount;
 import javax.annotation.Nonnull;
 import java.io.IOException;
 import java.nio.channels.ReadableByteChannel;
+import java.nio.file.attribute.BasicFileAttributes;
 import java.util.ArrayList;
 import java.util.HashSet;
 import java.util.List;
@@ -126,4 +127,19 @@ public class ComboMount implements IMount
         }
         throw new FileOperationException( path, "No such file" );
     }
+
+    @Nonnull
+    @Override
+    public BasicFileAttributes getAttributes( @Nonnull String path ) throws IOException
+    {
+        for( int i = m_parts.length - 1; i >= 0; --i )
+        {
+            IMount part = m_parts[i];
+            if( part.exists( path ) && !part.isDirectory( path ) )
+            {
+                return part.getAttributes( path );
+            }
+        }
+        throw new FileOperationException( path, "No such file" );
+    }
 }

src/main/java/dan200/computercraft/core/filesystem/FileMount.java

@@ -6,6 +6,7 @@
 package dan200.computercraft.core.filesystem;
 
 import com.google.common.collect.Sets;
+import dan200.computercraft.ComputerCraft;
 import dan200.computercraft.api.filesystem.FileOperationException;
 import dan200.computercraft.api.filesystem.IWritableMount;
 
@@ -14,11 +15,11 @@ import java.io.File;
 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.nio.channels.*;
-import java.nio.file.Files;
-import java.nio.file.OpenOption;
-import java.nio.file.StandardOpenOption;
+import java.nio.file.*;
+import java.nio.file.attribute.BasicFileAttributes;
 import java.util.Collections;
 import java.util.List;
+import java.util.OptionalLong;
 import java.util.Set;
 
 public class FileMount implements IWritableMount
@@ -211,6 +212,19 @@ public class FileMount implements IWritableMount
         throw new FileOperationException( path, "No such file" );
     }
 
+    @Nonnull
+    @Override
+    public BasicFileAttributes getAttributes( @Nonnull String path ) throws IOException
+    {
+        if( created() )
+        {
+            File file = getRealPath( path );
+            if( file.exists() ) return Files.readAttributes( file.toPath(), BasicFileAttributes.class );
+        }
+
+        throw new FileOperationException( path, "No such file" );
+    }
+
     // IWritableMount implementation
 
     @Override
@@ -331,6 +345,13 @@ public class FileMount implements IWritableMount
         return Math.max( m_capacity - m_usedSpace, 0 );
     }
 
+    @Nonnull
+    @Override
+    public OptionalLong getCapacity()
+    {
+        return OptionalLong.of( m_capacity - MINIMUM_FILE_SIZE );
+    }
+
     private File getRealPath( String path )
     {
         return new File( m_rootPath, path );
@@ -353,23 +374,46 @@ public class FileMount implements IWritableMount
         }
     }
 
+    private static class Visitor extends SimpleFileVisitor<Path>
+    {
+        long size;
+
+        @Override
+        public FileVisitResult preVisitDirectory( Path dir, BasicFileAttributes attrs )
+        {
+            size += MINIMUM_FILE_SIZE;
+            return FileVisitResult.CONTINUE;
+        }
+
+        @Override
+        public FileVisitResult visitFile( Path file, BasicFileAttributes attrs )
+        {
+            size += Math.max( attrs.size(), MINIMUM_FILE_SIZE );
+            return FileVisitResult.CONTINUE;
+        }
+
+        @Override
+        public FileVisitResult visitFileFailed( Path file, IOException exc )
+        {
+            ComputerCraft.log.error( "Error computing file size for {}", file, exc );
+            return FileVisitResult.CONTINUE;
+        }
+    }
+
     private static long measureUsedSpace( File file )
     {
         if( !file.exists() ) return 0;
 
-        if( file.isDirectory() )
+        try
         {
-            long size = MINIMUM_FILE_SIZE;
-            String[] contents = file.list();
-            for( String content : contents )
-            {
-                size += measureUsedSpace( new File( file, content ) );
-            }
-            return size;
+            Visitor visitor = new Visitor();
+            Files.walkFileTree( file.toPath(), visitor );
+            return visitor.size;
         }
-        else
+        catch( IOException e )
         {
-            return Math.max( file.length(), MINIMUM_FILE_SIZE );
+            ComputerCraft.log.error( "Error computing file size for {}", file, e );
+            return 0;
         }
     }
 }

src/main/java/dan200/computercraft/core/filesystem/FileSystem.java

@@ -7,7 +7,6 @@ package dan200.computercraft.core.filesystem;
 
 import com.google.common.io.ByteStreams;
 import dan200.computercraft.ComputerCraft;
-import dan200.computercraft.api.filesystem.FileOperationException;
 import dan200.computercraft.api.filesystem.IFileSystem;
 import dan200.computercraft.api.filesystem.IMount;
 import dan200.computercraft.api.filesystem.IWritableMount;
@@ -23,309 +22,23 @@ import java.nio.channels.Channel;
 import java.nio.channels.ReadableByteChannel;
 import java.nio.channels.WritableByteChannel;
 import java.nio.file.AccessDeniedException;
+import java.nio.file.attribute.BasicFileAttributes;
 import java.util.*;
 import java.util.function.Function;
 import java.util.regex.Pattern;
 
 public class FileSystem
 {
-    private static class MountWrapper
-    {
-        private String m_label;
-        private String m_location;
-
-        private IMount m_mount;
-        private IWritableMount m_writableMount;
-
-        MountWrapper( String label, String location, IMount mount )
-        {
-            m_label = label;
-            m_location = location;
-            m_mount = mount;
-            m_writableMount = null;
-        }
-
-        MountWrapper( String label, String location, IWritableMount mount )
-        {
-            this( label, location, (IMount) mount );
-            m_writableMount = mount;
-        }
-
-        public String getLabel()
-        {
-            return m_label;
-        }
-
-        public String getLocation()
-        {
-            return m_location;
-        }
-
-        public long getFreeSpace()
-        {
-            if( m_writableMount == null )
-            {
-                return 0;
-            }
-
-            try
-            {
-                return m_writableMount.getRemainingSpace();
-            }
-            catch( IOException e )
-            {
-                return 0;
-            }
-        }
-
-        public boolean isReadOnly( String path )
-        {
-            return m_writableMount == null;
-        }
-
-        // IMount forwarders:
-
-        public boolean exists( String path ) throws FileSystemException
-        {
-            path = toLocal( path );
-            try
-            {
-                return m_mount.exists( path );
-            }
-            catch( IOException e )
-            {
-                throw new FileSystemException( e.getMessage() );
-            }
-        }
-
-        public boolean isDirectory( String path ) throws FileSystemException
-        {
-            path = toLocal( path );
-            try
-            {
-                return m_mount.exists( path ) && m_mount.isDirectory( path );
-            }
-            catch( IOException e )
-            {
-                throw localExceptionOf( e );
-            }
-        }
-
-        public void list( String path, List<String> contents ) throws FileSystemException
-        {
-            path = toLocal( path );
-            try
-            {
-                if( m_mount.exists( path ) && m_mount.isDirectory( path ) )
-                {
-                    m_mount.list( path, contents );
-                }
-                else
-                {
-                    throw localExceptionOf( path, "Not a directory" );
-                }
-            }
-            catch( IOException e )
-            {
-                throw localExceptionOf( e );
-            }
-        }
-
-        public long getSize( String path ) throws FileSystemException
-        {
-            path = toLocal( path );
-            try
-            {
-                if( m_mount.exists( path ) )
-                {
-                    if( m_mount.isDirectory( path ) )
-                    {
-                        return 0;
-                    }
-                    else
-                    {
-                        return m_mount.getSize( path );
-                    }
-                }
-                else
-                {
-                    throw localExceptionOf( path, "No such file" );
-                }
-            }
-            catch( IOException e )
-            {
-                throw localExceptionOf( e );
-            }
-        }
-
-        public ReadableByteChannel openForRead( String path ) throws FileSystemException
-        {
-            path = toLocal( path );
-            try
-            {
-                if( m_mount.exists( path ) && !m_mount.isDirectory( path ) )
-                {
-                    return m_mount.openForRead( path );
-                }
-                else
-                {
-                    throw localExceptionOf( path, "No such file" );
-                }
-            }
-            catch( IOException e )
-            {
-                throw localExceptionOf( e );
-            }
-        }
-
-        // IWritableMount forwarders:
-
-        public void makeDirectory( String path ) throws FileSystemException
-        {
-            if( m_writableMount == null ) throw exceptionOf( path, "Access denied" );
-
-            path = toLocal( path );
-            try
-            {
-                if( m_mount.exists( path ) )
-                {
-                    if( !m_mount.isDirectory( path ) ) throw localExceptionOf( path, "File exists" );
-                }
-                else
-                {
-                    m_writableMount.makeDirectory( path );
-                }
-            }
-            catch( IOException e )
-            {
-                throw localExceptionOf( e );
-            }
-        }
-
-        public void delete( String path ) throws FileSystemException
-        {
-            if( m_writableMount == null ) throw exceptionOf( path, "Access denied" );
-
-            try
-            {
-                path = toLocal( path );
-                if( m_mount.exists( path ) )
-                {
-                    m_writableMount.delete( path );
-                }
-            }
-            catch( AccessDeniedException e )
-            {
-                throw new FileSystemException( "Access denied" );
-            }
-            catch( IOException e )
-            {
-                throw localExceptionOf( e );
-            }
-        }
-
-        public WritableByteChannel openForWrite( String path ) throws FileSystemException
-        {
-            if( m_writableMount == null ) throw exceptionOf( path, "Access denied" );
-
-            path = toLocal( path );
-            try
-            {
-                if( m_mount.exists( path ) && m_mount.isDirectory( path ) )
-                {
-                    throw localExceptionOf( path, "Cannot write to directory" );
-                }
-                else
-                {
-                    if( !path.isEmpty() )
-                    {
-                        String dir = getDirectory( path );
-                        if( !dir.isEmpty() && !m_mount.exists( path ) )
-                        {
-                            m_writableMount.makeDirectory( dir );
-                        }
-                    }
-                    return m_writableMount.openForWrite( path );
-                }
-            }
-            catch( AccessDeniedException e )
-            {
-                throw new FileSystemException( "Access denied" );
-            }
-            catch( IOException e )
-            {
-                throw localExceptionOf( e );
-            }
-        }
-
-        public WritableByteChannel openForAppend( String path ) throws FileSystemException
-        {
-            if( m_writableMount == null ) throw exceptionOf( path, "Access denied" );
-
-            path = toLocal( path );
-            try
-            {
-                if( !m_mount.exists( path ) )
-                {
-                    if( !path.isEmpty() )
-                    {
-                        String dir = getDirectory( path );
-                        if( !dir.isEmpty() && !m_mount.exists( path ) )
-                        {
-                            m_writableMount.makeDirectory( dir );
-                        }
-                    }
-                    return m_writableMount.openForWrite( path );
-                }
-                else if( m_mount.isDirectory( path ) )
-                {
-                    throw localExceptionOf( path, "Cannot write to directory" );
-                }
-                else
-                {
-                    return m_writableMount.openForAppend( path );
-                }
-            }
-            catch( AccessDeniedException e )
-            {
-                throw new FileSystemException( "Access denied" );
-            }
-            catch( IOException e )
-            {
-                throw localExceptionOf( e );
-            }
-        }
-
-        private String toLocal( String path )
-        {
-            return FileSystem.toLocal( path, m_location );
-        }
-
-        private FileSystemException localExceptionOf( IOException e )
-        {
-            if( !m_location.isEmpty() && e instanceof FileOperationException )
-            {
-                FileOperationException ex = (FileOperationException) e;
-                if( ex.getFilename() != null ) return localExceptionOf( ex.getFilename(), ex.getMessage() );
-            }
-
-            return new FileSystemException( e.getMessage() );
-        }
-
-        private FileSystemException localExceptionOf( String path, String message )
-        {
-            if( !m_location.isEmpty() ) path = path.isEmpty() ? m_location : m_location + "/" + path;
-            return exceptionOf( path, message );
-        }
-
-        private static FileSystemException exceptionOf( String path, String message )
-        {
-            return new FileSystemException( "/" + path + ": " + message );
-        }
-    }
+    /**
+     * Maximum depth that {@link #copyRecursive(String, MountWrapper, String, MountWrapper, int)} will descend into.
+     *
+     * This is a pretty arbitrary value, though hopefully it is large enough that it'll never be normally hit. This
+     * exists to prevent it overflowing if it ever gets into an infinite loop.
+     */
+    private static final int MAX_COPY_DEPTH = 128;
 
     private final FileSystemWrapperMount m_wrapper = new FileSystemWrapperMount( this );
-    private final Map<String, MountWrapper> m_mounts = new HashMap<>();
+    private final Map<String, MountWrapper> mounts = new HashMap<>();
 
     private final HashMap<WeakReference<FileSystemWrapper<?>>, ChannelWrapper<?>> m_openFiles = new HashMap<>();
     private final ReferenceQueue<FileSystemWrapper<?>> m_openFileQueue = new ReferenceQueue<>();
@@ -355,10 +68,7 @@ public class FileSystem
     {
         if( mount == null ) throw new NullPointerException();
         location = sanitizePath( location );
-        if( location.contains( ".." ) )
-        {
-            throw new FileSystemException( "Cannot mount below the root" );
-        }
+        if( location.contains( ".." ) ) throw new FileSystemException( "Cannot mount below the root" );
         mount( new MountWrapper( label, location, mount ) );
     }
 
@@ -379,14 +89,13 @@ public class FileSystem
     private synchronized void mount( MountWrapper wrapper )
     {
         String location = wrapper.getLocation();
-        m_mounts.remove( location );
-        m_mounts.put( location, wrapper );
+        mounts.remove( location );
+        mounts.put( location, wrapper );
     }
 
     public synchronized void unmount( String path )
     {
-        path = sanitizePath( path );
-        m_mounts.remove( path );
+        mounts.remove( sanitizePath( path ) );
     }
 
     public synchronized String combine( String path, String childPath )
@@ -430,27 +139,20 @@ public class FileSystem
     public static String getName( String path )
     {
         path = sanitizePath( path, true );
-        if( path.isEmpty() )
-        {
-            return "root";
-        }
+        if( path.isEmpty() ) return "root";
 
         int lastSlash = path.lastIndexOf( '/' );
-        if( lastSlash >= 0 )
-        {
-            return path.substring( lastSlash + 1 );
-        }
-        else
-        {
-            return path;
-        }
+        return lastSlash >= 0 ? path.substring( lastSlash + 1 ) : path;
     }
 
     public synchronized long getSize( String path ) throws FileSystemException
     {
-        path = sanitizePath( path );
-        MountWrapper mount = getMount( path );
-        return mount.getSize( path );
+        return getMount( sanitizePath( path ) ).getSize( sanitizePath( path ) );
+    }
+
+    public synchronized BasicFileAttributes getAttributes( String path ) throws FileSystemException
+    {
+        return getMount( sanitizePath( path ) ).getAttributes( sanitizePath( path ) );
     }
 
     public synchronized String[] list( String path ) throws FileSystemException
@@ -463,7 +165,7 @@ public class FileSystem
         mount.list( path, list );
 
         // Add any mounts that are mounted at this location
-        for( MountWrapper otherMount : m_mounts.values() )
+        for( MountWrapper otherMount : mounts.values() )
         {
             if( getDirectory( otherMount.getLocation() ).equals( path ) )
             {
@@ -611,15 +313,13 @@ public class FileSystem
         {
             throw new FileSystemException( "/" + sourcePath + ": Can't copy a directory inside itself" );
         }
-        copyRecursive( sourcePath, getMount( sourcePath ), destPath, getMount( destPath ) );
+        copyRecursive( sourcePath, getMount( sourcePath ), destPath, getMount( destPath ), 0 );
     }
 
-    private synchronized void copyRecursive( String sourcePath, MountWrapper sourceMount, String destinationPath, MountWrapper destinationMount ) throws FileSystemException
+    private synchronized void copyRecursive( String sourcePath, MountWrapper sourceMount, String destinationPath, MountWrapper destinationMount, int depth ) throws FileSystemException
     {
-        if( !sourceMount.exists( sourcePath ) )
-        {
-            return;
-        }
+        if( !sourceMount.exists( sourcePath ) ) return;
+        if( depth >= MAX_COPY_DEPTH ) throw new FileSystemException( "Too many directories to copy" );
 
         if( sourceMount.isDirectory( sourcePath ) )
         {
@@ -634,7 +334,8 @@ public class FileSystem
             {
                 copyRecursive(
                     combine( sourcePath, child ), sourceMount,
-                    combine( destinationPath, child ), destinationMount
+                    combine( destinationPath, child ), destinationMount,
+                    depth + 1
                 );
             }
         }
@@ -726,17 +427,25 @@ public class FileSystem
         return null;
     }
 
-    public long getFreeSpace( String path ) throws FileSystemException
+    public synchronized long getFreeSpace( String path ) throws FileSystemException
     {
         path = sanitizePath( path );
         MountWrapper mount = getMount( path );
         return mount.getFreeSpace();
     }
 
-    private MountWrapper getMount( String path ) throws FileSystemException
+    @Nonnull
+    public synchronized OptionalLong getCapacity( String path ) throws FileSystemException
+    {
+        path = sanitizePath( path );
+        MountWrapper mount = getMount( path );
+        return mount.getCapacity();
+    }
+
+    private synchronized MountWrapper getMount( String path ) throws FileSystemException
     {
         // Return the deepest mount that contains a given path
-        Iterator<MountWrapper> it = m_mounts.values().iterator();
+        Iterator<MountWrapper> it = mounts.values().iterator();
         MountWrapper match = null;
         int matchLength = 999;
         while( it.hasNext() )
@@ -854,8 +563,8 @@ public class FileSystem
 
     public static boolean contains( String pathA, String pathB )
     {
-        pathA = sanitizePath( pathA );
-        pathB = sanitizePath( pathB );
+        pathA = sanitizePath( pathA ).toLowerCase( Locale.ROOT );
+        pathB = sanitizePath( pathB ).toLowerCase( Locale.ROOT );
 
         if( pathB.equals( ".." ) )
         {

src/main/java/dan200/computercraft/core/filesystem/JarMount.java

@@ -23,6 +23,9 @@ import java.lang.ref.ReferenceQueue;
 import java.lang.ref.WeakReference;
 import java.nio.channels.Channels;
 import java.nio.channels.ReadableByteChannel;
+import java.nio.file.attribute.BasicFileAttributes;
+import java.nio.file.attribute.FileTime;
+import java.time.Instant;
 import java.util.Enumeration;
 import java.util.HashMap;
 import java.util.List;
@@ -213,6 +216,20 @@ public class JarMount implements IMount
         throw new FileOperationException( path, "No such file" );
     }
 
+    @Nonnull
+    @Override
+    public BasicFileAttributes getAttributes( @Nonnull String path ) throws IOException
+    {
+        FileEntry file = get( path );
+        if( file != null )
+        {
+            ZipEntry entry = zip.getEntry( file.path );
+            if( entry != null ) return new ZipEntryAttributes( entry );
+        }
+
+        throw new FileOperationException( path, "No such file" );
+    }
+
     private static class FileEntry
     {
         String path;
@@ -253,4 +270,76 @@ public class JarMount implements IMount
         Reference<? extends JarMount> next;
         while( (next = MOUNT_QUEUE.poll()) != null ) IoUtil.closeQuietly( ((MountReference) next).file );
     }
+
+    private static class ZipEntryAttributes implements BasicFileAttributes
+    {
+        private final ZipEntry entry;
+
+        ZipEntryAttributes( ZipEntry entry )
+        {
+            this.entry = entry;
+        }
+
+        @Override
+        public FileTime lastModifiedTime()
+        {
+            return orEpoch( entry.getLastModifiedTime() );
+        }
+
+        @Override
+        public FileTime lastAccessTime()
+        {
+            return orEpoch( entry.getLastAccessTime() );
+        }
+
+        @Override
+        public FileTime creationTime()
+        {
+            FileTime time = entry.getCreationTime();
+            return time == null ? lastModifiedTime() : time;
+        }
+
+        @Override
+        public boolean isRegularFile()
+        {
+            return !entry.isDirectory();
+        }
+
+        @Override
+        public boolean isDirectory()
+        {
+            return entry.isDirectory();
+        }
+
+        @Override
+        public boolean isSymbolicLink()
+        {
+            return false;
+        }
+
+        @Override
+        public boolean isOther()
+        {
+            return false;
+        }
+
+        @Override
+        public long size()
+        {
+            return entry.getSize();
+        }
+
+        @Override
+        public Object fileKey()
+        {
+            return null;
+        }
+
+        private static final FileTime EPOCH = FileTime.from( Instant.EPOCH );
+
+        private static FileTime orEpoch( FileTime time )
+        {
+            return time == null ? EPOCH : time;
+        }
+    }
 }

src/main/java/dan200/computercraft/core/filesystem/MountWrapper.java

@@ -0,0 +1,312 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2020. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+package dan200.computercraft.core.filesystem;
+
+import dan200.computercraft.api.filesystem.FileOperationException;
+import dan200.computercraft.api.filesystem.IMount;
+import dan200.computercraft.api.filesystem.IWritableMount;
+
+import javax.annotation.Nonnull;
+import java.io.IOException;
+import java.nio.channels.ReadableByteChannel;
+import java.nio.channels.WritableByteChannel;
+import java.nio.file.AccessDeniedException;
+import java.nio.file.attribute.BasicFileAttributes;
+import java.util.List;
+import java.util.OptionalLong;
+
+class MountWrapper
+{
+    private String label;
+    private String location;
+
+    private IMount mount;
+    private IWritableMount writableMount;
+
+    MountWrapper( String label, String location, IMount mount )
+    {
+        this.label = label;
+        this.location = location;
+        this.mount = mount;
+        writableMount = null;
+    }
+
+    MountWrapper( String label, String location, IWritableMount mount )
+    {
+        this( label, location, (IMount) mount );
+        writableMount = mount;
+    }
+
+    public String getLabel()
+    {
+        return label;
+    }
+
+    public String getLocation()
+    {
+        return location;
+    }
+
+    public long getFreeSpace()
+    {
+        if( writableMount == null ) return 0;
+
+        try
+        {
+            return writableMount.getRemainingSpace();
+        }
+        catch( IOException e )
+        {
+            return 0;
+        }
+    }
+
+    public OptionalLong getCapacity()
+    {
+        return writableMount == null ? OptionalLong.empty() : writableMount.getCapacity();
+    }
+
+    public boolean isReadOnly( String path )
+    {
+        return writableMount == null;
+    }
+
+    public boolean exists( String path ) throws FileSystemException
+    {
+        path = toLocal( path );
+        try
+        {
+            return mount.exists( path );
+        }
+        catch( IOException e )
+        {
+            throw new FileSystemException( e.getMessage() );
+        }
+    }
+
+    public boolean isDirectory( String path ) throws FileSystemException
+    {
+        path = toLocal( path );
+        try
+        {
+            return mount.exists( path ) && mount.isDirectory( path );
+        }
+        catch( IOException e )
+        {
+            throw localExceptionOf( e );
+        }
+    }
+
+    public void list( String path, List<String> contents ) throws FileSystemException
+    {
+        path = toLocal( path );
+        try
+        {
+            if( !mount.exists( path ) || !mount.isDirectory( path ) )
+            {
+                throw localExceptionOf( path, "Not a directory" );
+            }
+
+            mount.list( path, contents );
+        }
+        catch( IOException e )
+        {
+            throw localExceptionOf( e );
+        }
+    }
+
+    public long getSize( String path ) throws FileSystemException
+    {
+        path = toLocal( path );
+        try
+        {
+            if( !mount.exists( path ) ) throw localExceptionOf( path, "No such file" );
+            return mount.isDirectory( path ) ? 0 : mount.getSize( path );
+        }
+        catch( IOException e )
+        {
+            throw localExceptionOf( e );
+        }
+    }
+
+    @Nonnull
+    public BasicFileAttributes getAttributes( String path ) throws FileSystemException
+    {
+        path = toLocal( path );
+        try
+        {
+            if( !mount.exists( path ) ) throw localExceptionOf( path, "No such file" );
+            return mount.getAttributes( path );
+        }
+        catch( IOException e )
+        {
+            throw localExceptionOf( e );
+        }
+    }
+
+    public ReadableByteChannel openForRead( String path ) throws FileSystemException
+    {
+        path = toLocal( path );
+        try
+        {
+            if( mount.exists( path ) && !mount.isDirectory( path ) )
+            {
+                return mount.openChannelForRead( path );
+            }
+            else
+            {
+                throw localExceptionOf( path, "No such file" );
+            }
+        }
+        catch( IOException e )
+        {
+            throw localExceptionOf( e );
+        }
+    }
+
+    public void makeDirectory( String path ) throws FileSystemException
+    {
+        if( writableMount == null ) throw exceptionOf( path, "Access denied" );
+
+        path = toLocal( path );
+        try
+        {
+            if( mount.exists( path ) )
+            {
+                if( !mount.isDirectory( path ) ) throw localExceptionOf( path, "File exists" );
+            }
+            else
+            {
+                writableMount.makeDirectory( path );
+            }
+        }
+        catch( IOException e )
+        {
+            throw localExceptionOf( e );
+        }
+    }
+
+    public void delete( String path ) throws FileSystemException
+    {
+        if( writableMount == null ) throw exceptionOf( path, "Access denied" );
+
+        try
+        {
+            path = toLocal( path );
+            if( mount.exists( path ) )
+            {
+                writableMount.delete( path );
+            }
+        }
+        catch( AccessDeniedException e )
+        {
+            throw new FileSystemException( "Access denied" );
+        }
+        catch( IOException e )
+        {
+            throw localExceptionOf( e );
+        }
+    }
+
+    public WritableByteChannel openForWrite( String path ) throws FileSystemException
+    {
+        if( writableMount == null ) throw exceptionOf( path, "Access denied" );
+
+        path = toLocal( path );
+        try
+        {
+            if( mount.exists( path ) && mount.isDirectory( path ) )
+            {
+                throw localExceptionOf( path, "Cannot write to directory" );
+            }
+            else
+            {
+                if( !path.isEmpty() )
+                {
+                    String dir = FileSystem.getDirectory( path );
+                    if( !dir.isEmpty() && !mount.exists( path ) )
+                    {
+                        writableMount.makeDirectory( dir );
+                    }
+                }
+                return writableMount.openChannelForWrite( path );
+            }
+        }
+        catch( AccessDeniedException e )
+        {
+            throw new FileSystemException( "Access denied" );
+        }
+        catch( IOException e )
+        {
+            throw localExceptionOf( e );
+        }
+    }
+
+    public WritableByteChannel openForAppend( String path ) throws FileSystemException
+    {
+        if( writableMount == null ) throw exceptionOf( path, "Access denied" );
+
+        path = toLocal( path );
+        try
+        {
+            if( !mount.exists( path ) )
+            {
+                if( !path.isEmpty() )
+                {
+                    String dir = FileSystem.getDirectory( path );
+                    if( !dir.isEmpty() && !mount.exists( path ) )
+                    {
+                        writableMount.makeDirectory( dir );
+                    }
+                }
+                return writableMount.openChannelForWrite( path );
+            }
+            else if( mount.isDirectory( path ) )
+            {
+                throw localExceptionOf( path, "Cannot write to directory" );
+            }
+            else
+            {
+                return writableMount.openChannelForAppend( path );
+            }
+        }
+        catch( AccessDeniedException e )
+        {
+            throw new FileSystemException( "Access denied" );
+        }
+        catch( IOException e )
+        {
+            throw localExceptionOf( e );
+        }
+    }
+
+    private String toLocal( String path )
+    {
+        return FileSystem.toLocal( path, location );
+    }
+
+    private FileSystemException localExceptionOf( IOException e )
+    {
+        if( !location.isEmpty() && e instanceof FileOperationException )
+        {
+            FileOperationException ex = (FileOperationException) e;
+            if( ex.getFilename() != null ) return localExceptionOf( ex.getFilename(), ex.getMessage() );
+        }
+
+        return new FileSystemException( e.getMessage() );
+    }
+
+    private FileSystemException localExceptionOf( String path, String message )
+    {
+        if( !location.isEmpty() ) path = path.isEmpty() ? location : location + "/" + path;
+        return exceptionOf( path, message );
+    }
+
+    private static FileSystemException exceptionOf( String path, String message )
+    {
+        return new FileSystemException( "/" + path + ": " + message );
+    }
+}

src/main/java/dan200/computercraft/core/filesystem/SubMount.java

@@ -10,61 +10,60 @@ import dan200.computercraft.api.filesystem.IMount;
 import javax.annotation.Nonnull;
 import java.io.IOException;
 import java.nio.channels.ReadableByteChannel;
+import java.nio.file.attribute.BasicFileAttributes;
 import java.util.List;
 
 public class SubMount implements IMount
 {
-    private IMount m_parent;
-    private String m_subPath;
+    private IMount parent;
+    private String subPath;
 
     public SubMount( IMount parent, String subPath )
     {
-        m_parent = parent;
-        m_subPath = subPath;
+        this.parent = parent;
+        this.subPath = subPath;
     }
 
-    // IMount implementation
-
     @Override
     public boolean exists( @Nonnull String path ) throws IOException
     {
-        return m_parent.exists( getFullPath( path ) );
+        return parent.exists( getFullPath( path ) );
     }
 
     @Override
     public boolean isDirectory( @Nonnull String path ) throws IOException
     {
-        return m_parent.isDirectory( getFullPath( path ) );
+        return parent.isDirectory( getFullPath( path ) );
     }
 
     @Override
     public void list( @Nonnull String path, @Nonnull List<String> contents ) throws IOException
     {
-        m_parent.list( getFullPath( path ), contents );
+        parent.list( getFullPath( path ), contents );
     }
 
     @Override
     public long getSize( @Nonnull String path ) throws IOException
     {
-        return m_parent.getSize( getFullPath( path ) );
+        return parent.getSize( getFullPath( path ) );
     }
 
     @Nonnull
     @Override
     public ReadableByteChannel openForRead( @Nonnull String path ) throws IOException
     {
-        return m_parent.openForRead( getFullPath( path ) );
+        return parent.openForRead( getFullPath( path ) );
+    }
+
+    @Nonnull
+    @Override
+    public BasicFileAttributes getAttributes( @Nonnull String path ) throws IOException
+    {
+        return parent.getAttributes( getFullPath( path ) );
     }
 
     private String getFullPath( String path )
     {
-        if( path.isEmpty() )
-        {
-            return m_subPath;
-        }
-        else
-        {
-            return m_subPath + "/" + path;
-        }
+        return path.isEmpty() ? subPath : subPath + "/" + path;
     }
 }

src/main/java/dan200/computercraft/core/lua/CobaltLuaMachine.java

@@ -92,6 +92,7 @@ public class CobaltLuaMachine implements ILuaMachine
         m_globals.load( state, new MathLib() );
         m_globals.load( state, new CoroutineLib() );
         m_globals.load( state, new Bit32Lib() );
+        m_globals.load( state, new Utf8Lib() );
         if( ComputerCraft.debug_enable ) m_globals.load( state, new DebugLib() );
 
         // Remove globals we don't want to expose

src/main/java/dan200/computercraft/data/Generators.java

@@ -0,0 +1,28 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2020. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.data;
+
+import dan200.computercraft.shared.proxy.ComputerCraftProxyCommon;
+import net.minecraft.data.DataGenerator;
+import net.minecraftforge.eventbus.api.SubscribeEvent;
+import net.minecraftforge.fml.common.Mod;
+import net.minecraftforge.fml.event.lifecycle.GatherDataEvent;
+
+@Mod.EventBusSubscriber( bus = Mod.EventBusSubscriber.Bus.MOD )
+public class Generators
+{
+    @SubscribeEvent
+    public static void gather( GatherDataEvent event )
+    {
+        ComputerCraftProxyCommon.registerLoot();
+
+        DataGenerator generator = event.getGenerator();
+        generator.addProvider( new Recipes( generator ) );
+        generator.addProvider( new LootTables( generator ) );
+        generator.addProvider( new Tags( generator ) );
+    }
+}

src/main/java/dan200/computercraft/data/LootTableProvider.java

@@ -0,0 +1,91 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2020. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.data;
+
+import com.google.common.collect.Multimap;
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import dan200.computercraft.ComputerCraft;
+import net.minecraft.data.DataGenerator;
+import net.minecraft.data.DirectoryCache;
+import net.minecraft.data.IDataProvider;
+import net.minecraft.util.ResourceLocation;
+import net.minecraft.world.storage.loot.LootTable;
+import net.minecraft.world.storage.loot.LootTableManager;
+import net.minecraft.world.storage.loot.ValidationResults;
+
+import javax.annotation.Nonnull;
+import java.io.IOException;
+import java.nio.file.Path;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.function.BiConsumer;
+
+/**
+ * An alternative to {@link net.minecraft.data.LootTableProvider}, with a more flexible interface.
+ */
+public abstract class LootTableProvider implements IDataProvider
+{
+    private static final Gson GSON = new GsonBuilder().setPrettyPrinting().disableHtmlEscaping().create();
+
+    private final DataGenerator generator;
+
+    public LootTableProvider( DataGenerator generator )
+    {
+        this.generator = generator;
+    }
+
+    @Override
+    public void act( @Nonnull DirectoryCache cache )
+    {
+
+        ValidationResults validation = new ValidationResults();
+        Map<ResourceLocation, LootTable> tables = new HashMap<>();
+        registerLoot( ( id, table ) -> {
+            if( tables.containsKey( id ) ) validation.addProblem( "Duplicate loot tables for " + id );
+            tables.put( id, table );
+        } );
+
+        tables.forEach( ( key, value ) -> LootTableManager.func_215302_a( validation, key, value, tables::get ) );
+
+        Multimap<String, String> problems = validation.getProblems();
+        if( !problems.isEmpty() )
+        {
+            problems.forEach( ( child, problem ) ->
+                ComputerCraft.log.warn( "Found validation problem in " + child + ": " + problem ) );
+            throw new IllegalStateException( "Failed to validate loot tables, see logs" );
+        }
+
+        tables.forEach( ( key, value ) -> {
+            Path path = getPath( key );
+            try
+            {
+                IDataProvider.save( GSON, cache, LootTableManager.toJson( value ), path );
+            }
+            catch( IOException e )
+            {
+                ComputerCraft.log.error( "Couldn't save loot table {}", path, e );
+            }
+        } );
+    }
+
+    protected abstract void registerLoot( BiConsumer<ResourceLocation, LootTable> add );
+
+    @Nonnull
+    @Override
+    public String getName()
+    {
+        return "LootTables";
+    }
+
+    private Path getPath( ResourceLocation id )
+    {
+        return generator.getOutputFolder()
+            .resolve( "data" ).resolve( id.getNamespace() ).resolve( "loot_tables" )
+            .resolve( id.getPath() + ".json" );
+    }
+}

src/main/java/dan200/computercraft/data/LootTables.java

@@ -0,0 +1,72 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2020. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.data;
+
+import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.shared.data.BlockNamedEntityLootCondition;
+import dan200.computercraft.shared.data.PlayerCreativeLootCondition;
+import net.minecraft.block.Block;
+import net.minecraft.data.DataGenerator;
+import net.minecraft.util.ResourceLocation;
+import net.minecraft.world.storage.loot.*;
+import net.minecraft.world.storage.loot.conditions.Alternative;
+import net.minecraft.world.storage.loot.conditions.SurvivesExplosion;
+
+import java.util.function.BiConsumer;
+
+public class LootTables extends LootTableProvider
+{
+    public LootTables( DataGenerator generator )
+    {
+        super( generator );
+    }
+
+    @Override
+    protected void registerLoot( BiConsumer<ResourceLocation, LootTable> add )
+    {
+        basicDrop( add, ComputerCraft.Blocks.diskDrive );
+        basicDrop( add, ComputerCraft.Blocks.monitorNormal );
+        basicDrop( add, ComputerCraft.Blocks.monitorAdvanced );
+        basicDrop( add, ComputerCraft.Blocks.printer );
+        basicDrop( add, ComputerCraft.Blocks.speaker );
+        basicDrop( add, ComputerCraft.Blocks.wiredModemFull );
+        basicDrop( add, ComputerCraft.Blocks.wirelessModemNormal );
+        basicDrop( add, ComputerCraft.Blocks.wirelessModemAdvanced );
+
+        computerDrop( add, ComputerCraft.Blocks.computerNormal );
+        computerDrop( add, ComputerCraft.Blocks.computerAdvanced );
+        computerDrop( add, ComputerCraft.Blocks.turtleNormal );
+        computerDrop( add, ComputerCraft.Blocks.turtleAdvanced );
+    }
+
+    private static void basicDrop( BiConsumer<ResourceLocation, LootTable> add, Block block )
+    {
+        add.accept( block.getRegistryName(), LootTable
+            .builder()
+            .addLootPool( LootPool.builder()
+                .name( "main" )
+                .rolls( ConstantRange.of( 1 ) )
+                .addEntry( ItemLootEntry.builder( block ) )
+                .acceptCondition( SurvivesExplosion.builder() )
+            ).build() );
+    }
+
+    private static void computerDrop( BiConsumer<ResourceLocation, LootTable> add, Block block )
+    {
+        add.accept( block.getRegistryName(), LootTable
+            .builder()
+            .addLootPool( LootPool.builder()
+                .name( "main" )
+                .rolls( ConstantRange.of( 1 ) )
+                .addEntry( DynamicLootEntry.func_216162_a( new ResourceLocation( ComputerCraft.MOD_ID, "computer" ) ) )
+                .acceptCondition( Alternative.builder(
+                    BlockNamedEntityLootCondition.builder(),
+                    PlayerCreativeLootCondition.builder().inverted()
+                ) )
+            ).build() );
+    }
+}

src/main/java/dan200/computercraft/data/RecipeWrapper.java

@@ -0,0 +1,92 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2020. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.data;
+
+import com.google.gson.JsonObject;
+import net.minecraft.data.IFinishedRecipe;
+import net.minecraft.item.crafting.IRecipeSerializer;
+import net.minecraft.nbt.CompoundNBT;
+import net.minecraft.util.JSONUtils;
+import net.minecraft.util.ResourceLocation;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import java.util.function.Consumer;
+
+/**
+ * Adapter for recipes which overrides the serializer and adds custom item NBT.
+ */
+public final class RecipeWrapper implements IFinishedRecipe
+{
+    private final IFinishedRecipe recipe;
+    private final CompoundNBT resultData;
+    private final IRecipeSerializer<?> serializer;
+
+    private RecipeWrapper( IFinishedRecipe recipe, CompoundNBT resultData, IRecipeSerializer<?> serializer )
+    {
+        this.resultData = resultData;
+        this.recipe = recipe;
+        this.serializer = serializer;
+    }
+
+    public static Consumer<IFinishedRecipe> wrap( IRecipeSerializer<?> serializer, Consumer<IFinishedRecipe> original )
+    {
+        return x -> original.accept( new RecipeWrapper( x, null, serializer ) );
+    }
+
+    public static Consumer<IFinishedRecipe> wrap( IRecipeSerializer<?> serializer, Consumer<IFinishedRecipe> original, CompoundNBT resultData )
+    {
+        return x -> original.accept( new RecipeWrapper( x, resultData, serializer ) );
+    }
+
+    public static Consumer<IFinishedRecipe> wrap( IRecipeSerializer<?> serializer, Consumer<IFinishedRecipe> original, Consumer<CompoundNBT> resultData )
+    {
+        CompoundNBT tag = new CompoundNBT();
+        resultData.accept( tag );
+        return x -> original.accept( new RecipeWrapper( x, tag, serializer ) );
+    }
+
+    @Override
+    public void serialize( @Nonnull JsonObject jsonObject )
+    {
+        recipe.serialize( jsonObject );
+
+        if( resultData != null )
+        {
+            JsonObject object = JSONUtils.getJsonObject( jsonObject, "result" );
+            object.addProperty( "nbt", resultData.toString() );
+        }
+    }
+
+    @Nonnull
+    @Override
+    public ResourceLocation getID()
+    {
+        return recipe.getID();
+    }
+
+    @Nonnull
+    @Override
+    public IRecipeSerializer<?> getSerializer()
+    {
+        return serializer;
+    }
+
+    @Nullable
+    @Override
+    public JsonObject getAdvancementJson()
+    {
+        return recipe.getAdvancementJson();
+    }
+
+    @Nullable
+    @Override
+    public ResourceLocation getAdvancementID()
+    {
+        return recipe.getAdvancementID();
+    }
+}

src/main/java/dan200/computercraft/data/Recipes.java

@@ -0,0 +1,320 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2020. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.data;
+
+import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.data.Tags.CCTags;
+import dan200.computercraft.shared.TurtleUpgrades;
+import dan200.computercraft.shared.computer.core.ComputerFamily;
+import dan200.computercraft.shared.pocket.items.PocketComputerItemFactory;
+import dan200.computercraft.shared.turtle.items.TurtleItemFactory;
+import dan200.computercraft.shared.util.Colour;
+import dan200.computercraft.shared.util.ImpostorRecipe;
+import dan200.computercraft.shared.util.ImpostorShapelessRecipe;
+import net.minecraft.advancements.criterion.InventoryChangeTrigger;
+import net.minecraft.advancements.criterion.ItemPredicate;
+import net.minecraft.block.Blocks;
+import net.minecraft.data.*;
+import net.minecraft.item.*;
+import net.minecraft.tags.Tag;
+import net.minecraft.util.IItemProvider;
+import net.minecraft.util.ResourceLocation;
+import net.minecraftforge.common.Tags;
+
+import javax.annotation.Nonnull;
+import java.util.Locale;
+import java.util.function.Consumer;
+
+public class Recipes extends RecipeProvider
+{
+    public Recipes( DataGenerator generator )
+    {
+        super( generator );
+    }
+
+    @Override
+    protected void registerRecipes( @Nonnull Consumer<IFinishedRecipe> add )
+    {
+        basicRecipes( add );
+        diskColours( add );
+        pocketUpgrades( add );
+        turtleUpgrades( add );
+    }
+
+    /**
+     * Register a crafting recipe for a disk of every dye colour.
+     *
+     * @param add The callback to add recipes.
+     */
+    private void diskColours( @Nonnull Consumer<IFinishedRecipe> add )
+    {
+        for( Colour colour : Colour.VALUES )
+        {
+            ShapelessRecipeBuilder
+                .shapelessRecipe( ComputerCraft.Items.disk )
+                .addIngredient( Tags.Items.DUSTS_REDSTONE )
+                .addIngredient( Items.PAPER )
+                .addIngredient( DyeItem.getItem( ofColour( colour ) ) )
+                .setGroup( "computercraft:disk" )
+                .addCriterion( "has_drive", inventoryChange( ComputerCraft.Blocks.diskDrive ) )
+                .build( RecipeWrapper.wrap(
+                    ImpostorShapelessRecipe.SERIALIZER, add,
+                    x -> x.putInt( "color", colour.getHex() )
+                ), new ResourceLocation( ComputerCraft.MOD_ID, "disk_" + (colour.ordinal() + 1) ) );
+        }
+    }
+
+    /**
+     * Register a crafting recipe for each turtle upgrade.
+     *
+     * @param add The callback to add recipes.
+     */
+    private void turtleUpgrades( @Nonnull Consumer<IFinishedRecipe> add )
+    {
+        for( ComputerFamily family : ComputerFamily.values() )
+        {
+            ItemStack base = TurtleItemFactory.create( -1, null, -1, family, null, null, 0, null );
+            if( base.isEmpty() ) continue;
+
+            String nameId = family.name().toLowerCase( Locale.ROOT );
+
+            TurtleUpgrades.getVanillaUpgrades().forEach( upgrade -> {
+                ItemStack result = TurtleItemFactory.create( -1, null, -1, family, null, upgrade, -1, null );
+                ShapedRecipeBuilder
+                    .shapedRecipe( result.getItem() )
+                    .setGroup( String.format( "%s:turtle_%s", ComputerCraft.MOD_ID, nameId ) )
+                    .patternLine( "#T" )
+                    .key( '#', base.getItem() )
+                    .key( 'T', upgrade.getCraftingItem().getItem() )
+                    .addCriterion( "has_items",
+                        inventoryChange( base.getItem(), upgrade.getCraftingItem().getItem() ) )
+                    .build(
+                        RecipeWrapper.wrap( ImpostorRecipe.SERIALIZER, add, result.getTag() ),
+                        new ResourceLocation( ComputerCraft.MOD_ID, String.format( "turtle_%s/%s/%s",
+                            nameId, upgrade.getUpgradeID().getNamespace(), upgrade.getUpgradeID().getPath()
+                        ) )
+                    );
+            } );
+        }
+    }
+
+    /**
+     * Register a crafting recipe for each pocket upgrade.
+     *
+     * @param add The callback to add recipes.
+     */
+    private void pocketUpgrades( @Nonnull Consumer<IFinishedRecipe> add )
+    {
+        for( ComputerFamily family : ComputerFamily.values() )
+        {
+            ItemStack base = PocketComputerItemFactory.create( -1, null, -1, family, null );
+            if( base.isEmpty() ) continue;
+
+            String nameId = family.name().toLowerCase( Locale.ROOT );
+
+            TurtleUpgrades.getVanillaUpgrades().forEach( upgrade -> {
+                ItemStack result = PocketComputerItemFactory.create( -1, null, -1, family, null );
+                ShapedRecipeBuilder
+                    .shapedRecipe( result.getItem() )
+                    .setGroup( String.format( "%s:pocket_%s", ComputerCraft.MOD_ID, nameId ) )
+                    .patternLine( "#" )
+                    .patternLine( "P" )
+                    .key( '#', base.getItem() )
+                    .key( 'P', upgrade.getCraftingItem().getItem() )
+                    .addCriterion( "has_items",
+                        inventoryChange( base.getItem(), upgrade.getCraftingItem().getItem() ) )
+                    .build(
+                        RecipeWrapper.wrap( ImpostorRecipe.SERIALIZER, add, result.getTag() ),
+                        new ResourceLocation( ComputerCraft.MOD_ID, String.format( "pocket_%s/%s/%s",
+                            nameId, upgrade.getUpgradeID().getNamespace(), upgrade.getUpgradeID().getPath()
+                        ) )
+                    );
+            } );
+        }
+    }
+
+    private void basicRecipes( @Nonnull Consumer<IFinishedRecipe> add )
+    {
+        ShapedRecipeBuilder
+            .shapedRecipe( ComputerCraft.Items.cable, 6 )
+            .patternLine( " # " )
+            .patternLine( "#R#" )
+            .patternLine( " # " )
+            .key( '#', Tags.Items.STONE )
+            .key( 'R', Tags.Items.DUSTS_REDSTONE )
+            .addCriterion( "has_computer", inventoryChange( CCTags.COMPUTER ) )
+            .addCriterion( "has_modem", inventoryChange( CCTags.COMPUTER ) )
+            .build( add );
+
+        ShapedRecipeBuilder
+            .shapedRecipe( ComputerCraft.Blocks.computerNormal )
+            .patternLine( "###" )
+            .patternLine( "#R#" )
+            .patternLine( "#G#" )
+            .key( '#', Tags.Items.STONE )
+            .key( 'R', Tags.Items.DUSTS_REDSTONE )
+            .key( 'G', Tags.Items.GLASS_PANES )
+            .addCriterion( "has_redstone", inventoryChange( Tags.Items.DUSTS_REDSTONE ) )
+            .build( add );
+
+        ShapedRecipeBuilder
+            .shapedRecipe( ComputerCraft.Blocks.computerAdvanced )
+            .patternLine( "###" )
+            .patternLine( "#R#" )
+            .patternLine( "#G#" )
+            .key( '#', Tags.Items.INGOTS_GOLD )
+            .key( 'R', Tags.Items.DUSTS_REDSTONE )
+            .key( 'G', Tags.Items.GLASS_PANES )
+            .addCriterion( "has_components", inventoryChange( Items.REDSTONE, Items.GOLD_INGOT ) )
+            .build( add );
+
+        ShapedRecipeBuilder
+            .shapedRecipe( ComputerCraft.Blocks.computerCommand )
+            .patternLine( "###" )
+            .patternLine( "#R#" )
+            .patternLine( "#G#" )
+            .key( '#', Tags.Items.INGOTS_GOLD )
+            .key( 'R', Blocks.COMMAND_BLOCK )
+            .key( 'G', Tags.Items.GLASS_PANES )
+            .addCriterion( "has_components", inventoryChange( Blocks.COMMAND_BLOCK ) )
+            .build( add );
+
+        ShapedRecipeBuilder
+            .shapedRecipe( ComputerCraft.Blocks.diskDrive )
+            .patternLine( "###" )
+            .patternLine( "#R#" )
+            .patternLine( "#R#" )
+            .key( '#', Tags.Items.STONE )
+            .key( 'R', Tags.Items.DUSTS_REDSTONE )
+            .addCriterion( "has_computer", inventoryChange( CCTags.COMPUTER ) )
+            .build( add );
+
+        ShapedRecipeBuilder
+            .shapedRecipe( ComputerCraft.Blocks.monitorNormal )
+            .patternLine( "###" )
+            .patternLine( "#G#" )
+            .patternLine( "###" )
+            .key( '#', Tags.Items.STONE )
+            .key( 'G', Tags.Items.GLASS_PANES )
+            .addCriterion( "has_computer", inventoryChange( CCTags.COMPUTER ) )
+            .build( add );
+
+        ShapedRecipeBuilder
+            .shapedRecipe( ComputerCraft.Blocks.monitorAdvanced, 4 )
+            .patternLine( "###" )
+            .patternLine( "#G#" )
+            .patternLine( "###" )
+            .key( '#', Tags.Items.INGOTS_GOLD )
+            .key( 'G', Tags.Items.GLASS_PANES )
+            .addCriterion( "has_computer", inventoryChange( CCTags.COMPUTER ) )
+            .build( add );
+
+        ShapedRecipeBuilder
+            .shapedRecipe( ComputerCraft.Items.pocketComputerNormal )
+            .patternLine( "###" )
+            .patternLine( "#A#" )
+            .patternLine( "#G#" )
+            .key( '#', Tags.Items.STONE )
+            .key( 'A', Items.GOLDEN_APPLE )
+            .key( 'G', Tags.Items.GLASS_PANES )
+            .addCriterion( "has_computer", inventoryChange( CCTags.COMPUTER ) )
+            .addCriterion( "has_apple", inventoryChange( Items.GOLDEN_APPLE ) )
+            .build( add );
+
+        ShapedRecipeBuilder
+            .shapedRecipe( ComputerCraft.Items.pocketComputerAdvanced )
+            .patternLine( "###" )
+            .patternLine( "#A#" )
+            .patternLine( "#G#" )
+            .key( '#', Tags.Items.INGOTS_GOLD )
+            .key( 'A', Items.GOLDEN_APPLE )
+            .key( 'G', Tags.Items.GLASS_PANES )
+            .addCriterion( "has_computer", inventoryChange( CCTags.COMPUTER ) )
+            .addCriterion( "has_apple", inventoryChange( Items.GOLDEN_APPLE ) )
+            .build( add );
+
+        ShapedRecipeBuilder
+            .shapedRecipe( ComputerCraft.Blocks.printer )
+            .patternLine( "###" )
+            .patternLine( "#R#" )
+            .patternLine( "#D#" )
+            .key( '#', Tags.Items.STONE )
+            .key( 'R', Tags.Items.DUSTS_REDSTONE )
+            .key( 'D', Tags.Items.DYES )
+            .addCriterion( "has_computer", inventoryChange( CCTags.COMPUTER ) )
+            .build( add );
+
+        ShapedRecipeBuilder
+            .shapedRecipe( ComputerCraft.Blocks.speaker )
+            .patternLine( "###" )
+            .patternLine( "#N#" )
+            .patternLine( "#R#" )
+            .key( '#', Tags.Items.STONE )
+            .key( 'N', Blocks.NOTE_BLOCK )
+            .key( 'R', Tags.Items.DUSTS_REDSTONE )
+            .addCriterion( "has_computer", inventoryChange( CCTags.COMPUTER ) )
+            .build( add );
+
+        ShapedRecipeBuilder
+            .shapedRecipe( ComputerCraft.Items.wiredModem )
+            .patternLine( "###" )
+            .patternLine( "#R#" )
+            .patternLine( "###" )
+            .key( '#', Tags.Items.STONE )
+            .key( 'R', Tags.Items.DUSTS_REDSTONE )
+            .addCriterion( "has_computer", inventoryChange( CCTags.COMPUTER ) )
+            .addCriterion( "has_cable", inventoryChange( ComputerCraft.Items.cable ) )
+            .build( add );
+
+        ShapelessRecipeBuilder
+            .shapelessRecipe( ComputerCraft.Blocks.wiredModemFull )
+            .addIngredient( ComputerCraft.Items.wiredModem )
+            .addCriterion( "has_modem", inventoryChange( CCTags.WIRED_MODEM ) )
+            .build( add, new ResourceLocation( ComputerCraft.MOD_ID, "wired_modem_full_from" ) );
+        ShapelessRecipeBuilder
+            .shapelessRecipe( ComputerCraft.Items.wiredModem )
+            .addIngredient( ComputerCraft.Blocks.wiredModemFull )
+            .addCriterion( "has_modem", inventoryChange( CCTags.WIRED_MODEM ) )
+            .build( add, new ResourceLocation( ComputerCraft.MOD_ID, "wired_modem_full_to" ) );
+
+        ShapedRecipeBuilder
+            .shapedRecipe( ComputerCraft.Blocks.wirelessModemNormal )
+            .patternLine( "###" )
+            .patternLine( "#E#" )
+            .patternLine( "###" )
+            .key( '#', Tags.Items.STONE )
+            .key( 'E', Tags.Items.ENDER_PEARLS )
+            .addCriterion( "has_computer", inventoryChange( CCTags.COMPUTER ) )
+            .build( add );
+
+        ShapedRecipeBuilder
+            .shapedRecipe( ComputerCraft.Blocks.wirelessModemAdvanced )
+            .patternLine( "###" )
+            .patternLine( "#E#" )
+            .patternLine( "###" )
+            .key( '#', Tags.Items.INGOTS_GOLD )
+            .key( 'E', Items.ENDER_EYE )
+            .addCriterion( "has_computer", inventoryChange( CCTags.COMPUTER ) )
+            .addCriterion( "has_wireless", inventoryChange( ComputerCraft.Blocks.wirelessModemNormal ) )
+            .build( add );
+    }
+
+    private static DyeColor ofColour( Colour colour )
+    {
+        return DyeColor.byId( 15 - colour.ordinal() );
+    }
+
+    private static InventoryChangeTrigger.Instance inventoryChange( Tag<Item> stack )
+    {
+        return InventoryChangeTrigger.Instance.forItems( ItemPredicate.Builder.create().tag( stack ).build() );
+    }
+
+    private static InventoryChangeTrigger.Instance inventoryChange( IItemProvider... stack )
+    {
+        return InventoryChangeTrigger.Instance.forItems( stack );
+    }
+}

src/main/java/dan200/computercraft/data/Tags.java

@@ -0,0 +1,52 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2020. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.data;
+
+import dan200.computercraft.ComputerCraft;
+import net.minecraft.data.DataGenerator;
+import net.minecraft.data.ItemTagsProvider;
+import net.minecraft.item.Item;
+import net.minecraft.tags.ItemTags;
+import net.minecraft.tags.Tag;
+import net.minecraft.util.ResourceLocation;
+
+import static dan200.computercraft.data.Tags.CCTags.*;
+
+public class Tags extends ItemTagsProvider
+{
+    public static class CCTags
+    {
+        public static final Tag<Item> COMPUTER = item( "computer" );
+        public static final Tag<Item> TURTLE = item( "turtle" );
+        public static final Tag<Item> WIRED_MODEM = item( "wired_modem" );
+        public static final Tag<Item> MONITOR = item( "monitor" );
+    }
+
+    public Tags( DataGenerator generator )
+    {
+        super( generator );
+    }
+
+    @Override
+    protected void registerTags()
+    {
+        getBuilder( COMPUTER )
+            .add( ComputerCraft.Items.computerNormal )
+            .add( ComputerCraft.Items.computerAdvanced )
+            .add( ComputerCraft.Items.computerCommand );
+        getBuilder( TURTLE ).add( ComputerCraft.Items.turtleNormal, ComputerCraft.Items.turtleAdvanced );
+        getBuilder( WIRED_MODEM ).add( ComputerCraft.Items.wiredModem, ComputerCraft.Blocks.wiredModemFull.asItem() );
+        getBuilder( MONITOR )
+            .add( ComputerCraft.Blocks.monitorNormal.asItem() )
+            .add( ComputerCraft.Blocks.monitorAdvanced.asItem() );
+    }
+
+    private static Tag<Item> item( String name )
+    {
+        return new ItemTags.Wrapper( new ResourceLocation( ComputerCraft.MOD_ID, name ) );
+    }
+}

src/main/java/dan200/computercraft/shared/Config.java

@@ -38,42 +38,42 @@ public final class Config
 
     private static final String TRANSLATION_PREFIX = "gui.computercraft.config.";
 
-    private static ConfigValue<Integer> computerSpaceLimit;
-    private static ConfigValue<Integer> floppySpaceLimit;
-    private static ConfigValue<Integer> maximumFilesOpen;
-    private static ConfigValue<Boolean> disableLua51Features;
-    private static ConfigValue<String> defaultComputerSettings;
-    private static ConfigValue<Boolean> debugEnabled;
-    private static ConfigValue<Boolean> logComputerErrors;
+    private static final ConfigValue<Integer> computerSpaceLimit;
+    private static final ConfigValue<Integer> floppySpaceLimit;
+    private static final ConfigValue<Integer> maximumFilesOpen;
+    private static final ConfigValue<Boolean> disableLua51Features;
+    private static final ConfigValue<String> defaultComputerSettings;
+    private static final ConfigValue<Boolean> debugEnabled;
+    private static final ConfigValue<Boolean> logComputerErrors;
 
-    private static ConfigValue<Integer> computerThreads;
-    private static ConfigValue<Integer> maxMainGlobalTime;
-    private static ConfigValue<Integer> maxMainComputerTime;
+    private static final ConfigValue<Integer> computerThreads;
+    private static final ConfigValue<Integer> maxMainGlobalTime;
+    private static final ConfigValue<Integer> maxMainComputerTime;
 
-    private static ConfigValue<Boolean> httpEnabled;
-    private static ConfigValue<Boolean> httpWebsocketEnabled;
-    private static ConfigValue<List<? extends UnmodifiableConfig>> httpRules;
+    private static final ConfigValue<Boolean> httpEnabled;
+    private static final ConfigValue<Boolean> httpWebsocketEnabled;
+    private static final ConfigValue<List<? extends UnmodifiableConfig>> httpRules;
 
-    private static ConfigValue<Integer> httpTimeout;
-    private static ConfigValue<Integer> httpMaxRequests;
-    private static ConfigValue<Integer> httpMaxDownload;
-    private static ConfigValue<Integer> httpMaxUpload;
-    private static ConfigValue<Integer> httpMaxWebsockets;
-    private static ConfigValue<Integer> httpMaxWebsocketMessage;
+    private static final ConfigValue<Integer> httpTimeout;
+    private static final ConfigValue<Integer> httpMaxRequests;
+    private static final ConfigValue<Integer> httpMaxDownload;
+    private static final ConfigValue<Integer> httpMaxUpload;
+    private static final ConfigValue<Integer> httpMaxWebsockets;
+    private static final ConfigValue<Integer> httpMaxWebsocketMessage;
 
-    private static ConfigValue<Boolean> commandBlockEnabled;
-    private static ConfigValue<Integer> modemRange;
-    private static ConfigValue<Integer> modemHighAltitudeRange;
-    private static ConfigValue<Integer> modemRangeDuringStorm;
-    private static ConfigValue<Integer> modemHighAltitudeRangeDuringStorm;
-    private static ConfigValue<Integer> maxNotesPerTick;
+    private static final ConfigValue<Boolean> commandBlockEnabled;
+    private static final ConfigValue<Integer> modemRange;
+    private static final ConfigValue<Integer> modemHighAltitudeRange;
+    private static final ConfigValue<Integer> modemRangeDuringStorm;
+    private static final ConfigValue<Integer> modemHighAltitudeRangeDuringStorm;
+    private static final ConfigValue<Integer> maxNotesPerTick;
 
-    private static ConfigValue<Boolean> turtlesNeedFuel;
-    private static ConfigValue<Integer> turtleFuelLimit;
-    private static ConfigValue<Integer> advancedTurtleFuelLimit;
-    private static ConfigValue<Boolean> turtlesObeyBlockProtection;
-    private static ConfigValue<Boolean> turtlesCanPush;
-    private static ConfigValue<List<? extends String>> turtleDisabledActions;
+    private static final ConfigValue<Boolean> turtlesNeedFuel;
+    private static final ConfigValue<Integer> turtleFuelLimit;
+    private static final ConfigValue<Integer> advancedTurtleFuelLimit;
+    private static final ConfigValue<Boolean> turtlesObeyBlockProtection;
+    private static final ConfigValue<Boolean> turtlesCanPush;
+    private static final ConfigValue<List<? extends String>> turtleDisabledActions;
 
     private static final ForgeConfigSpec spec;
 

src/main/java/dan200/computercraft/shared/data/BlockNamedEntityLootCondition.java

@@ -40,4 +40,9 @@ public final class BlockNamedEntityLootCondition implements ILootCondition
     {
         return Collections.singleton( LootParameters.BLOCK_ENTITY );
     }
+
+    public static IBuilder builder()
+    {
+        return () -> INSTANCE;
+    }
 }

src/main/java/dan200/computercraft/shared/data/PlayerCreativeLootCondition.java

@@ -40,4 +40,9 @@ public final class PlayerCreativeLootCondition implements ILootCondition
     {
         return Collections.singleton( LootParameters.THIS_ENTITY );
     }
+
+    public static IBuilder builder()
+    {
+        return () -> INSTANCE;
+    }
 }

src/main/java/dan200/computercraft/shared/peripheral/monitor/ClientMonitor.java

@@ -16,7 +16,7 @@ import java.util.HashSet;
 import java.util.Iterator;
 import java.util.Set;
 
-public class ClientMonitor extends ClientTerminal
+public final class ClientMonitor extends ClientTerminal
 {
     private static final Set<ClientMonitor> allMonitors = new HashSet<>();
 
@@ -24,7 +24,8 @@ public class ClientMonitor extends ClientTerminal
 
     public long lastRenderFrame = -1;
     public BlockPos lastRenderPos = null;
-    public VertexBuffer buffer = null;
+
+    public VertexBuffer buffer;
 
     public ClientMonitor( boolean colour, TileMonitor origin )
     {
@@ -37,16 +38,45 @@ public class ClientMonitor extends ClientTerminal
         return origin;
     }
 
+    /**
+     * Create the appropriate buffer if needed.
+     *
+     * @param renderer The renderer to use. This can be fetched from {@link MonitorRenderer#current()}.
+     * @return If a buffer was created. This will return {@code false} if we already have an appropriate buffer,
+     * or this mode does not require one.
+     */
     @OnlyIn( Dist.CLIENT )
-    public void createBuffer()
+    public boolean createBuffer( MonitorRenderer renderer )
     {
-        if( buffer == null )
+        switch( renderer )
         {
-            buffer = new VertexBuffer( FixedWidthFontRenderer.TYPE.getVertexFormat() );
-            synchronized( allMonitors )
-            {
-                allMonitors.add( this );
-            }
+            case VBO:
+                if( buffer != null ) return false;
+
+                deleteBuffers();
+                buffer = new VertexBuffer( FixedWidthFontRenderer.POSITION_COLOR_TEX );
+                addMonitor();
+                return true;
+
+            default:
+                return false;
+        }
+    }
+
+    private void addMonitor()
+    {
+        synchronized( allMonitors )
+        {
+            allMonitors.add( this );
+        }
+    }
+
+    private void deleteBuffers()
+    {
+        if( buffer != null )
+        {
+            buffer.close();
+            buffer = null;
         }
     }
 
@@ -60,8 +90,7 @@ public class ClientMonitor extends ClientTerminal
                 allMonitors.remove( this );
             }
 
-            buffer.close();
-            buffer = null;
+            deleteBuffers();
         }
     }
 
@@ -73,11 +102,7 @@ public class ClientMonitor extends ClientTerminal
             for( Iterator<ClientMonitor> iterator = allMonitors.iterator(); iterator.hasNext(); )
             {
                 ClientMonitor monitor = iterator.next();
-                if( monitor.buffer != null )
-                {
-                    monitor.buffer.close();
-                    monitor.buffer = null;
-                }
+                monitor.deleteBuffers();
 
                 iterator.remove();
             }

src/main/java/dan200/computercraft/shared/peripheral/monitor/MonitorRenderer.java

@@ -0,0 +1,98 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2020. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.shared.peripheral.monitor;
+
+import com.mojang.blaze3d.platform.GLX;
+import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.client.render.TileEntityMonitorRenderer;
+
+import javax.annotation.Nonnull;
+import java.util.Locale;
+
+/**
+ * The render type to use for monitors.
+ *
+ * @see TileEntityMonitorRenderer
+ * @see ClientMonitor
+ */
+public enum MonitorRenderer
+{
+    /**
+     * Determine the best monitor backend.
+     */
+    BEST,
+
+    /**
+     * Render using VBOs.
+     *
+     * @see net.minecraft.client.renderer.vertex.VertexBuffer
+     */
+    VBO;
+
+    private static final MonitorRenderer[] VALUES = values();
+    public static final String[] NAMES;
+
+    private final String displayName = "gui.computercraft:config.peripheral.monitor_renderer." + name().toLowerCase( Locale.ROOT );
+
+    static
+    {
+        NAMES = new String[VALUES.length];
+        for( int i = 0; i < VALUES.length; i++ ) NAMES[i] = VALUES[i].displayName();
+    }
+
+    public String displayName()
+    {
+        return displayName;
+    }
+
+    @Nonnull
+    public static MonitorRenderer ofString( String name )
+    {
+        for( MonitorRenderer backend : VALUES )
+        {
+            if( backend.displayName.equalsIgnoreCase( name ) || backend.name().equalsIgnoreCase( name ) )
+            {
+                return backend;
+            }
+        }
+
+        ComputerCraft.log.warn( "Unknown monitor renderer {}. Falling back to default.", name );
+        return BEST;
+    }
+
+    /**
+     * Get the current renderer to use.
+     *
+     * @return The current renderer. Will not return {@link MonitorRenderer#BEST}.
+     */
+    @Nonnull
+    public static MonitorRenderer current()
+    {
+        MonitorRenderer current = ComputerCraft.monitorRenderer;
+        switch( current )
+        {
+            case BEST:
+                return best();
+            case VBO:
+                if( !GLX.useVbo() )
+                {
+                    ComputerCraft.log.warn( "VBOs are not supported on your graphics card. Falling back to default." );
+                    ComputerCraft.monitorRenderer = BEST;
+                    return best();
+                }
+
+                return VBO;
+            default:
+                return current;
+        }
+    }
+
+    private static MonitorRenderer best()
+    {
+        return VBO;
+    }
+}

src/main/java/dan200/computercraft/shared/proxy/ComputerCraftProxyCommon.java

@@ -45,14 +45,20 @@ import net.minecraftforge.fml.event.server.FMLServerStoppedEvent;
 public final class ComputerCraftProxyCommon
 {
     @SubscribeEvent
+    @SuppressWarnings( "deprecation" )
     public static void init( FMLCommonSetupEvent event )
     {
         NetworkHandler.setup();
 
-        registerProviders();
-
-        ArgumentSerializers.register();
+        net.minecraftforge.fml.DeferredWorkQueue.runLater( () -> {
+            registerProviders();
+            ArgumentSerializers.register();
+            registerLoot();
+        } );
+    }
 
+    public static void registerLoot()
+    {
         LootConditionManager.registerCondition( ConstantLootConditionSerializer.of(
             new ResourceLocation( ComputerCraft.MOD_ID, "block_named" ),
             BlockNamedEntityLootCondition.class,

src/main/java/dan200/computercraft/shared/util/Palette.java

@@ -48,13 +48,13 @@ public class Palette
     {
         if( i >= 0 && i < colours.length )
         {
-            setColour( i, Colour.values()[i] );
+            setColour( i, Colour.VALUES[i] );
         }
     }
 
     public void resetColours()
     {
-        for( int i = 0; i < Colour.values().length; i++ )
+        for( int i = 0; i < Colour.VALUES.length; i++ )
         {
             resetColour( i );
         }

src/main/java/dan200/computercraft/shared/util/WorldUtil.java

@@ -7,7 +7,6 @@ package dan200.computercraft.shared.util;
 
 import com.google.common.base.Predicate;
 import com.google.common.collect.MapMaker;
-import net.minecraft.block.BlockState;
 import net.minecraft.entity.*;
 import net.minecraft.entity.item.ItemEntity;
 import net.minecraft.entity.player.PlayerEntity;
@@ -54,8 +53,7 @@ public final class WorldUtil
     public static boolean isLiquidBlock( World world, BlockPos pos )
     {
         if( !World.isValid( pos ) ) return false;
-        BlockState state = world.getBlockState( pos );
-        return !state.getFluidState().isEmpty();
+        return world.getBlockState( pos ).getMaterial().isLiquid();
     }
 
     public static boolean isVecInside( VoxelShape shape, Vec3d vec )