src/Pure/General/xz.scala

--- a/src/Pure/General/xz.scala	Fri Apr 20 15:58:02 2018 +0200
+++ b/src/Pure/General/xz.scala	Fri Apr 20 22:17:42 2018 +0200
@@ -7,11 +7,13 @@
 package isabelle
 
 
-import org.tukaani.xz.LZMA2Options
+import org.tukaani.xz.{LZMA2Options, ArrayCache, BasicArrayCache}
 
 
 object XZ
 {
+  /* options */
+
   type Options = LZMA2Options
 
   def options(preset: Int = 3): Options =
@@ -20,4 +22,12 @@
     opts.setPreset(preset)
     opts
   }
+
+
+  /* cache */
+
+  type Cache = ArrayCache
+
+  def cache(): ArrayCache = ArrayCache.getDefaultCache()
+  def make_cache(): ArrayCache = new BasicArrayCache
 }