--- /dev/null	2018-11-30 10:10:44.238550338 +0100
+++ new/src/hotspot/share/gc/shenandoah/shenandoahCollectionSet.hpp	2018-11-30 10:22:43.686440188 +0100
@@ -0,0 +1,96 @@
+/*
+ * Copyright (c) 2016, 2018, Red Hat, Inc. All rights reserved.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#ifndef SHARE_VM_GC_SHENANDOAH_SHENANDOAHCOLLECTIONSET_HPP
+#define SHARE_VM_GC_SHENANDOAH_SHENANDOAHCOLLECTIONSET_HPP
+
+#include "memory/allocation.hpp"
+#include "gc/shenandoah/shenandoahHeap.hpp"
+#include "gc/shenandoah/shenandoahHeapRegion.hpp"
+
+class ShenandoahCollectionSet : public CHeapObj<mtGC> {
+  friend class ShenandoahHeap;
+private:
+  size_t const          _map_size;
+  size_t const          _region_size_bytes_shift;
+  jbyte* const          _cset_map;
+  // Bias cset map's base address for fast test if an oop is in cset
+  jbyte* const          _biased_cset_map;
+
+  ShenandoahHeap* const _heap;
+
+  size_t                _garbage;
+  size_t                _live_data;
+  size_t                _used;
+  size_t                _region_count;
+
+  DEFINE_PAD_MINUS_SIZE(0, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile size_t));
+  volatile jint         _current_index;
+  DEFINE_PAD_MINUS_SIZE(1, DEFAULT_CACHE_LINE_SIZE, 0);
+
+public:
+  ShenandoahCollectionSet(ShenandoahHeap* heap, HeapWord* heap_base);
+
+  // Add region to collection set
+  void add_region(ShenandoahHeapRegion* r);
+  bool add_region_check_for_duplicates(ShenandoahHeapRegion* r);
+
+  // Bring per-region statuses to consistency with this collection.
+  // TODO: This is a transitional interface that bridges the gap between
+  // region statuses and this collection. Should go away after we merge them.
+  void update_region_status();
+
+  // Remove region from collection set
+  void remove_region(ShenandoahHeapRegion* r);
+
+  // MT version
+  ShenandoahHeapRegion* claim_next();
+
+  // Single-thread version
+  ShenandoahHeapRegion* next();
+
+  size_t count()  const { return _region_count; }
+  bool is_empty() const { return _region_count == 0; }
+
+  void clear_current_index() {
+    _current_index = 0;
+  }
+
+  inline bool is_in(ShenandoahHeapRegion* r) const;
+  inline bool is_in(size_t region_number)    const;
+  inline bool is_in(HeapWord* p)             const;
+
+  void print_on(outputStream* out) const;
+
+  size_t used()      const { return _used; }
+  size_t live_data() const { return _live_data; }
+  size_t garbage()   const { return _garbage;   }
+  void clear();
+
+private:
+  jbyte* biased_map_address() const {
+    return _biased_cset_map;
+  }
+};
+
+#endif //SHARE_VM_GC_SHENANDOAH_SHENANDOAHCOLLECTIONSET_HPP