Impose additional limitations on disk and computer labels

Closes #147

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

@@ -8,6 +8,7 @@
 
 import dan200.computercraft.api.lua.ILuaContext;
 import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.shared.util.StringUtil;
 
 import java.util.Arrays;
 import java.util.HashMap;
@@ -266,11 +267,7 @@ public Object[] callMethod( ILuaContext context, int method, Object[] args ) thr
                     {
                         throw new LuaException( "Expected string or nil" );
                     }
-                    label = (String)args[0];
+                    label = StringUtil.normaliseLabel( (String) args[0] );
-                    if( label.length() > 32 )
-                    {
-                        label = label.substring( 0, 32 );
-                    }
                 }
                 m_apiEnvironment.setLabel( label );
                 return null;

src/main/java/dan200/computercraft/shared/peripheral/diskdrive/DiskDrivePeripheral.java

@@ -12,6 +12,7 @@
 import dan200.computercraft.api.peripheral.IComputerAccess;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.shared.media.items.ItemDiskLegacy;
+import dan200.computercraft.shared.util.StringUtil;
 import net.minecraft.item.Item;
 import net.minecraft.item.ItemStack;
 
@@ -87,6 +88,7 @@ public Object[] callMethod( IComputerAccess computer, ILuaContext context, int m
                 if( media != null )
                 {
                     ItemStack disk = m_diskDrive.getDiskStack();
+                    label = StringUtil.normaliseLabel( label );
                     if( media.setLabel( disk, label ) )
                     {
                         m_diskDrive.setDiskStack( disk );

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

@@ -0,0 +1,20 @@
+package dan200.computercraft.shared.util;
+
+import java.util.regex.Pattern;
+
+public class StringUtil
+{
+    private static final Pattern INVALID_PATTERN = Pattern.compile( "[^ -~]" );
+
+    public static String normaliseLabel( String label )
+    {
+        label = INVALID_PATTERN.matcher( label ).replaceAll( "" );
+
+        if( label.length() > 32 )
+        {
+            label = label.substring( 0, 32 );
+        }
+
+        return label;
+    }
+}