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   /*
    * Copyright 2016 The Netty Project
    *
    * The Netty Project licenses this file to you 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:
    *
    *   https://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 io.netty.channel.kqueue;
  
  import io.netty.channel.unix.Buffer;
  import io.netty.util.internal.PlatformDependent;
  
  import java.nio.ByteBuffer;
  
  import static io.netty.channel.unix.Limits.SIZEOF_JLONG;
  import static io.netty.util.internal.ObjectUtil.checkPositive;
  
  final class NativeLongArray {
      private ByteBuffer memory;
      private long memoryAddress;
      private int capacity;
      private int size;
  
      NativeLongArray(int capacity) {
          this.capacity = checkPositive(capacity, "capacity");
          memory = Buffer.allocateDirectWithNativeOrder(calculateBufferCapacity(capacity));
          memoryAddress = Buffer.memoryAddress(memory);
      }
  
      private static int idx(int index) {
          return index * SIZEOF_JLONG;
      }
  
      private static int calculateBufferCapacity(int capacity) {
          return capacity * SIZEOF_JLONG;
      }
  
      void add(long value) {
          reallocIfNeeded();
          if (PlatformDependent.hasUnsafe()) {
              PlatformDependent.putLong(memoryOffset(size), value);
          } else {
              memory.putLong(idx(size), value);
          }
          ++size;
      }
  
      void clear() {
          size = 0;
      }
  
      boolean isEmpty() {
          return size == 0;
      }
  
      int size() {
          return size;
      }
  
      void free() {
          Buffer.free(memory);
          memoryAddress = 0;
      }
  
      long memoryAddress() {
          return memoryAddress;
      }
  
      long memoryAddressEnd() {
          return memoryOffset(size);
      }
  
      private long memoryOffset(int index) {
          return memoryAddress + idx(index);
      }
  
      private void reallocIfNeeded() {
          if (size == capacity) {
              // Double the capacity while it is "sufficiently small", and otherwise increase by 50%.
              int newLength = capacity <= 65536 ? capacity << 1 : capacity + capacity >> 1;
              ByteBuffer buffer = Buffer.allocateDirectWithNativeOrder(calculateBufferCapacity(newLength));
              // Copy over the old content of the memory and reset the position as we always act on the buffer as if
              // the position was never increased.
              memory.position(0).limit(size);
              buffer.put(memory);
              buffer.position(0);
  
              Buffer.free(memory);
              memory = buffer;
              memoryAddress = Buffer.memoryAddress(buffer);
              capacity = newLength;
         }
     }
 
     @Override
     public String toString() {
         return "memoryAddress: " + memoryAddress + " capacity: " + capacity + " size: " + size;
     }
 }