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   /*
    * Copyright 2012 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:
    *
    *   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 io.netty.buffer;
  
  import io.netty.util.Recycler;
  
  import java.nio.ByteBuffer;
  import java.nio.ByteOrder;
  
  abstract class PooledByteBuf<T> extends AbstractReferenceCountedByteBuf {
  
      private final Recycler.Handle recyclerHandle;
  
      protected PoolChunk<T> chunk;
      protected long handle;
      protected T memory;
      protected int offset;
      protected int length;
      int maxLength;
      PoolThreadCache cache;
      private ByteBuffer tmpNioBuf;
      private ByteBufAllocator allocator;
  
      protected PooledByteBuf(Recycler.Handle recyclerHandle, int maxCapacity) {
          super(maxCapacity);
          this.recyclerHandle = recyclerHandle;
      }
  
      void init(PoolChunk<T> chunk, long handle, int offset, int length, int maxLength, PoolThreadCache cache) {
          init0(chunk, handle, offset, length, maxLength, cache);
      }
  
      void initUnpooled(PoolChunk<T> chunk, int length) {
          init0(chunk, 0, chunk.offset, length, length, null);
      }
  
      private void init0(PoolChunk<T> chunk, long handle, int offset, int length, int maxLength, PoolThreadCache cache) {
          assert handle >= 0;
          assert chunk != null;
  
          this.chunk = chunk;
          memory = chunk.memory;
          allocator = chunk.arena.parent;
          this.cache = cache;
          this.handle = handle;
          this.offset = offset;
          this.length = length;
          this.maxLength = maxLength;
          tmpNioBuf = null;
      }
  
      /**
       * Method must be called before reuse this {@link PooledByteBufAllocator}
       */
      final void reuse(int maxCapacity) {
          maxCapacity(maxCapacity);
          setRefCnt(1);
          setIndex0(0, 0);
          discardMarks();
      }
  
      @Override
      public final int capacity() {
          return length;
      }
  
      @Override
      public final ByteBuf capacity(int newCapacity) {
          checkNewCapacity(newCapacity);
  
          // If the request capacity does not require reallocation, just update the length of the memory.
          if (chunk.unpooled) {
              if (newCapacity == length) {
                  return this;
              }
          } else {
              if (newCapacity > length) {
                  if (newCapacity <= maxLength) {
                      length = newCapacity;
                      return this;
                  }
              } else if (newCapacity < length) {
                  if (newCapacity > maxLength >>> 1) {
                      if (maxLength <= 512) {
                          if (newCapacity > maxLength - 16) {
                             length = newCapacity;
                             setIndex(Math.min(readerIndex(), newCapacity), Math.min(writerIndex(), newCapacity));
                             return this;
                         }
                     } else { // > 512 (i.e. >= 1024)
                         length = newCapacity;
                         setIndex(Math.min(readerIndex(), newCapacity), Math.min(writerIndex(), newCapacity));
                         return this;
                     }
                 }
             } else {
                 return this;
             }
         }
 
         // Reallocation required.
         chunk.arena.reallocate(this, newCapacity, true);
         return this;
     }
 
     @Override
     public final ByteBufAllocator alloc() {
         return allocator;
     }
 
     @Override
     public final ByteOrder order() {
         return ByteOrder.BIG_ENDIAN;
     }
 
     @Override
     public final ByteBuf unwrap() {
         return null;
     }
 
     protected final ByteBuffer internalNioBuffer() {
         ByteBuffer tmpNioBuf = this.tmpNioBuf;
         if (tmpNioBuf == null) {
             this.tmpNioBuf = tmpNioBuf = newInternalNioBuffer(memory);
         }
         return tmpNioBuf;
     }
 
     protected abstract ByteBuffer newInternalNioBuffer(T memory);
 
     @Override
     protected final void deallocate() {
         if (handle >= 0) {
             final long handle = this.handle;
             this.handle = -1;
             memory = null;
             tmpNioBuf = null;
             chunk.arena.free(chunk, handle, maxLength, cache);
             chunk = null;
             recycle();
         }
     }
 
     private void recycle() {
         Recycler.Handle recyclerHandle = this.recyclerHandle;
         if (recyclerHandle != null) {
             ((Recycler<Object>) recycler()).recycle(this, recyclerHandle);
         }
     }
 
     protected abstract Recycler<?> recycler();
 
     protected final int idx(int index) {
         return offset + index;
     }
 }