--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/memory/metaspace/blockListArray.hpp	Sat Nov 23 11:05:16 2019 +0100
@@ -0,0 +1,154 @@
+/*
+ * Copyright (c) 2019, SAP SE. All rights reserved.
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * 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_MEMORY_METASPACE_BLOCKLISTARRAY_HPP
+#define SHARE_MEMORY_METASPACE_BLOCKLISTARRAY_HPP
+
+#include "memory/allocation.hpp"
+#include "utilities/debug.hpp"
+#include "utilities/globalDefinitions.hpp"
+
+
+class outputStream;
+
+namespace metaspace {
+
+struct block_t {
+  block_t* next;
+  size_t size;
+};
+
+struct block_stats_t {
+  size_t word_size;
+  int num_blocks;
+};
+
+// A bitmap keeping track of which list is occupied. Smallest list corresponds to lowest order bit.
+// 1 means list is not empty, 0 means list is empty.
+class BlockListFreeMap {
+
+  typedef uint32_t mask_type;
+  mask_type _mask;
+
+  static mask_type mask_for_pos(int pos) { return 1 << pos; }
+
+public:
+
+  BlockListFreeMap() : _mask(0) {}
+
+  bool all_zero() const          { return _mask == 0; }
+
+  bool get_bit(int pos) const    { return (_mask & mask_for_pos(pos)) != 0 ? true : false; }
+  void set_bit(int pos)          { _mask |= mask_for_pos(pos); }
+  void clr_bit(int pos)          { _mask &= ~mask_for_pos(pos); }
+
+  // Starting at (including) pos, find the position of the next 1 bit.
+  // Return -1 if not found.
+  inline int find_next_set_bit(int pos) const;
+
+  static int size() { return sizeof(mask_type) * 8; }
+
+};
+
+template <
+  size_t min_word_size,
+  size_t spread,
+  int num_bins
+>
+class BlockListArray {
+
+  STATIC_ASSERT(sizeof(block_t) <= (min_word_size * BytesPerWord));
+
+  block_t* _bins[num_bins];
+
+  BlockListFreeMap _map;
+
+  // e.g. spread = 4
+  //
+  // sz    bno (put)  bno (get)
+  //         (guarant)
+  // 0     00         00
+  // 1     00         01
+  // 2     00         01
+  // 3     00         01
+  // 4     01         01
+  // 5     01         02
+  // 6     01         02
+  // 7     01         02
+  // 8     02         02
+  // 9     02         03
+  // 10    02         03
+  // 11    02         03
+  //
+  // put -> no = wordsize / spread
+  //
+  // get -> no = (req_wordsize + spread - 1) / spread
+
+  // The bin number for a given word size.
+  static int bin_for_size(size_t word_size) {
+    assert(word_size >= min_word_size && word_size < maximal_word_size(),
+           "Word size oob (" SIZE_FORMAT ")", word_size);
+    return (word_size - min_word_size) / spread;
+  }
+
+  // [minimal, maximal) size of blocks which are held in a bin.
+  // Note that when taking a block out of the bin, only the minimum block size
+  // is guaranteed.
+  static size_t minimal_word_size_in_bin(int bno) {
+    return min_word_size + (bno * spread);
+  }
+  static size_t maximal_word_size_in_bin(int bno) {
+    return minimal_word_size_in_bin(bno) + spread;
+  }
+
+public:
+
+  BlockListArray() : _map() {
+    assert(BlockListFreeMap::size() >= num_bins, "Map too small.");
+    ::memset(_bins, 0, sizeof(_bins));
+  }
+
+  // [min, max) word size
+  static size_t minimal_word_size() { return min_word_size; }
+  static size_t maximal_word_size() { return min_word_size + (spread * num_bins); }
+
+  inline void put(MetaWord* p, size_t word_size);
+
+  inline block_t* get(size_t word_size);
+
+#ifdef ASSERT
+  void verify() const;
+#endif
+
+  void statistics(block_stats_t* stats) const;
+
+  void print(outputStream* st) const;
+
+};
+
+
+} // namespace metaspace
+
+#endif // SHARE_MEMORY_METASPACE_BLOCKLISTARRAY_HPP