code: /*
   * Copyright 2012-2018 Chronicle Map Contributors
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package net.openhft.chronicle.hash.impl;
  
  import net.openhft.chronicle.core.Memory;
  import net.openhft.chronicle.core.OS;
  
  import static net.openhft.chronicle.assertions.AssertUtil.SKIP_ASSERTIONS;
  import static net.openhft.chronicle.map.internal.InternalAssertUtil.assertAddress;
  
  /**
   * The reason why this is not implemented via value interface, and offsets are allocated by hand --
   * this functionality is accessed concurrently from many threads, and native value implementations
   * are stateful - so need to keep an instance in thread local that seems to be overall more pain
   * than gain.
   */
  public enum TierCountersArea {
      ; // none
  
      public static final long NEXT_TIER_INDEX_OFFSET = 0L;
      public static final long PREV_TIER_INDEX_OFFSET = NEXT_TIER_INDEX_OFFSET + 8L;
      public static final long LOWEST_POSSIBLY_FREE_CHUNK_TIERED_OFFSET = PREV_TIER_INDEX_OFFSET + 8L;
      public static final long SEGMENT_INDEX_OFFSET = LOWEST_POSSIBLY_FREE_CHUNK_TIERED_OFFSET + 8L;
      public static final long TIER_OFFSET = SEGMENT_INDEX_OFFSET + 4L;
      public static final long ENTRIES_OFFSET = TIER_OFFSET + 4L;
      public static final long DELETED_OFFSET = ENTRIES_OFFSET + 4L;
      private static final long UNSIGNED_INT_MASK = 0xFFFFFFFFL;
      private static final Memory MEMORY = OS.memory();
  
      public static long nextTierIndex(final long address) {
          assert SKIP_ASSERTIONS || assertAddress(address);
          return MEMORY.readLong(address + NEXT_TIER_INDEX_OFFSET);
      }
  
      public static void nextTierIndex(final long address,
                                       final long nextTierIndex) {
          assert SKIP_ASSERTIONS || assertAddress(address);
          MEMORY.writeLong(address + NEXT_TIER_INDEX_OFFSET, nextTierIndex);
      }
  
      public static long lowestPossiblyFreeChunkTiered(final long address) {
          assert SKIP_ASSERTIONS || assertAddress(address);
          return MEMORY.readLong(address + LOWEST_POSSIBLY_FREE_CHUNK_TIERED_OFFSET);
      }
  
      public static void lowestPossiblyFreeChunkTiered(final long address, final long lowestPossiblyFreeChunk) {
          assert SKIP_ASSERTIONS || assertAddress(address);
          MEMORY.writeLong(address + LOWEST_POSSIBLY_FREE_CHUNK_TIERED_OFFSET,
                  lowestPossiblyFreeChunk);
      }
  
      public static long prevTierIndex(final long address) {
          assert SKIP_ASSERTIONS || assertAddress(address);
          return MEMORY.readLong(address + PREV_TIER_INDEX_OFFSET);
      }
  
      public static void prevTierIndex(final long address,
                                       final long prevTierIndex) {
          assert SKIP_ASSERTIONS || assertAddress(address);
          MEMORY.writeLong(address + PREV_TIER_INDEX_OFFSET, prevTierIndex);
      }
  
      public static int segmentIndex(final long address) {
          assert SKIP_ASSERTIONS || assertAddress(address);
          return MEMORY.readInt(address + SEGMENT_INDEX_OFFSET);
      }
  
      public static void segmentIndex(final long address, final int segmentIndex) {
          assert SKIP_ASSERTIONS || assertAddress(address);
          MEMORY.writeInt(address + SEGMENT_INDEX_OFFSET, segmentIndex);
      }
  
      public static int tier(final long address) {
          assert SKIP_ASSERTIONS || assertAddress(address);
          return MEMORY.readInt(address + TIER_OFFSET);
      }
  
      public static void tier(final long address,
                              final int tier) {
          assert SKIP_ASSERTIONS || assertAddress(address);
          MEMORY.writeInt(address + TIER_OFFSET, tier);
      }
  
      public static long entries(final long address) {
          assert SKIP_ASSERTIONS || assertAddress(address);
          return MEMORY.readInt(address + ENTRIES_OFFSET) & UNSIGNED_INT_MASK;
      }
  
      public static void entries(final long address,
                                 final long entries) {
          assert SKIP_ASSERTIONS || assertAddress(address);
          if (entries >= (1L << 32)) {
              throw new IllegalStateException("tier entries overflow: up to " + UNSIGNED_INT_MASK +
                      " supported, " + entries + " given");
          }
          MEMORY.writeInt(address + ENTRIES_OFFSET, (int) entries);
      }
  
      public static long deleted(final long address) {
          assert SKIP_ASSERTIONS || assertAddress(address);
          return MEMORY.readInt(address + DELETED_OFFSET) & UNSIGNED_INT_MASK;
      }
  
      public static void deleted(final long address,
                                 final long deleted) {
          assert SKIP_ASSERTIONS || assertAddress(address);
          if (deleted >= (1L << 32)) {
              throw new IllegalStateException("tier deleted entries count overflow: up to " +
                      UNSIGNED_INT_MASK + " supported, " + deleted + " given");
          }
          MEMORY.writeInt(address + DELETED_OFFSET, (int) deleted);
      }
  }
  