查看本类的 API文档回源码主页

   /*
    * 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.ResourceLeakDetector;
  import io.netty.util.ResourceLeakTracker;
  import io.netty.util.internal.PlatformDependent;
  import io.netty.util.internal.StringUtil;
  
  /**
   * Skeletal {@link ByteBufAllocator} implementation to extend.
   */
  public abstract class AbstractByteBufAllocator implements ByteBufAllocator {
      static final int DEFAULT_INITIAL_CAPACITY = 256;
      static final int DEFAULT_MAX_CAPACITY = Integer.MAX_VALUE;
      static final int DEFAULT_MAX_COMPONENTS = 16;
      static final int CALCULATE_THRESHOLD = 1048576 * 4; // 4 MiB page
  
      static {
          ResourceLeakDetector.addExclusions(AbstractByteBufAllocator.class, "toLeakAwareBuffer");
      }
  
      protected static ByteBuf toLeakAwareBuffer(ByteBuf buf) {
          ResourceLeakTracker<ByteBuf> leak;
          switch (ResourceLeakDetector.getLevel()) {
              case SIMPLE:
                  leak = AbstractByteBuf.leakDetector.track(buf);
                  if (leak != null) {
                      buf = new SimpleLeakAwareByteBuf(buf, leak);
                  }
                  break;
              case ADVANCED:
              case PARANOID:
                  leak = AbstractByteBuf.leakDetector.track(buf);
                  if (leak != null) {
                      buf = new AdvancedLeakAwareByteBuf(buf, leak);
                  }
                  break;
          }
          return buf;
      }
  
      protected static CompositeByteBuf toLeakAwareBuffer(CompositeByteBuf buf) {
          ResourceLeakTracker<ByteBuf> leak;
          switch (ResourceLeakDetector.getLevel()) {
              case SIMPLE:
                  leak = AbstractByteBuf.leakDetector.track(buf);
                  if (leak != null) {
                      buf = new SimpleLeakAwareCompositeByteBuf(buf, leak);
                  }
                  break;
              case ADVANCED:
              case PARANOID:
                  leak = AbstractByteBuf.leakDetector.track(buf);
                  if (leak != null) {
                      buf = new AdvancedLeakAwareCompositeByteBuf(buf, leak);
                  }
                  break;
              default:
                  break;
          }
          return buf;
      }
  
      private final boolean directByDefault;
      private final ByteBuf emptyBuf;
  
      /**
       * Instance use heap buffers by default
       */
      protected AbstractByteBufAllocator() {
          this(false);
      }
  
      /**
       * Create new instance
       *
       * @param preferDirect {@code true} if {@link #buffer(int)} should try to allocate a direct buffer rather than
       *                     a heap buffer
       */
      protected AbstractByteBufAllocator(boolean preferDirect) {
          directByDefault = preferDirect && PlatformDependent.hasUnsafe();
          emptyBuf = new EmptyByteBuf(this);
      }
  
     @Override
     public ByteBuf buffer() {
         if (directByDefault) {
             return directBuffer();
         }
         return heapBuffer();
     }
 
     @Override
     public ByteBuf buffer(int initialCapacity) {
         if (directByDefault) {
             return directBuffer(initialCapacity);
         }
         return heapBuffer(initialCapacity);
     }
 
     @Override
     public ByteBuf buffer(int initialCapacity, int maxCapacity) {
         if (directByDefault) {
             return directBuffer(initialCapacity, maxCapacity);
         }
         return heapBuffer(initialCapacity, maxCapacity);
     }
 
     @Override
     public ByteBuf ioBuffer() {
         if (PlatformDependent.hasUnsafe()) {
             return directBuffer(DEFAULT_INITIAL_CAPACITY);
         }
         return heapBuffer(DEFAULT_INITIAL_CAPACITY);
     }
 
     @Override
     public ByteBuf ioBuffer(int initialCapacity) {
         if (PlatformDependent.hasUnsafe()) {
             return directBuffer(initialCapacity);
         }
         return heapBuffer(initialCapacity);
     }
 
     @Override
     public ByteBuf ioBuffer(int initialCapacity, int maxCapacity) {
         if (PlatformDependent.hasUnsafe()) {
             return directBuffer(initialCapacity, maxCapacity);
         }
         return heapBuffer(initialCapacity, maxCapacity);
     }
 
     @Override
     public ByteBuf heapBuffer() {
         return heapBuffer(DEFAULT_INITIAL_CAPACITY, DEFAULT_MAX_CAPACITY);
     }
 
     @Override
     public ByteBuf heapBuffer(int initialCapacity) {
         return heapBuffer(initialCapacity, DEFAULT_MAX_CAPACITY);
     }
 
     @Override
     public ByteBuf heapBuffer(int initialCapacity, int maxCapacity) {
         if (initialCapacity == 0 && maxCapacity == 0) {
             return emptyBuf;
         }
         validate(initialCapacity, maxCapacity);
         return newHeapBuffer(initialCapacity, maxCapacity);
     }
 
     @Override
     public ByteBuf directBuffer() {
         return directBuffer(DEFAULT_INITIAL_CAPACITY, DEFAULT_MAX_CAPACITY);
     }
 
     @Override
     public ByteBuf directBuffer(int initialCapacity) {
         return directBuffer(initialCapacity, DEFAULT_MAX_CAPACITY);
     }
 
     @Override
     public ByteBuf directBuffer(int initialCapacity, int maxCapacity) {
         if (initialCapacity == 0 && maxCapacity == 0) {
             return emptyBuf;
         }
         validate(initialCapacity, maxCapacity);
         return newDirectBuffer(initialCapacity, maxCapacity);
     }
 
     @Override
     public CompositeByteBuf compositeBuffer() {
         if (directByDefault) {
             return compositeDirectBuffer();
         }
         return compositeHeapBuffer();
     }
 
     @Override
     public CompositeByteBuf compositeBuffer(int maxNumComponents) {
         if (directByDefault) {
             return compositeDirectBuffer(maxNumComponents);
         }
         return compositeHeapBuffer(maxNumComponents);
     }
 
     @Override
     public CompositeByteBuf compositeHeapBuffer() {
         return compositeHeapBuffer(DEFAULT_MAX_COMPONENTS);
     }
 
     @Override
     public CompositeByteBuf compositeHeapBuffer(int maxNumComponents) {
         return toLeakAwareBuffer(new CompositeByteBuf(this, false, maxNumComponents));
     }
 
     @Override
     public CompositeByteBuf compositeDirectBuffer() {
         return compositeDirectBuffer(DEFAULT_MAX_COMPONENTS);
     }
 
     @Override
     public CompositeByteBuf compositeDirectBuffer(int maxNumComponents) {
         return toLeakAwareBuffer(new CompositeByteBuf(this, true, maxNumComponents));
     }
 
     private static void validate(int initialCapacity, int maxCapacity) {
         if (initialCapacity < 0) {
             throw new IllegalArgumentException("initialCapacity: " + initialCapacity + " (expected: 0+)");
         }
         if (initialCapacity > maxCapacity) {
             throw new IllegalArgumentException(String.format(
                     "initialCapacity: %d (expected: not greater than maxCapacity(%d)",
                     initialCapacity, maxCapacity));
         }
     }
 
     /**
      * Create a heap {@link ByteBuf} with the given initialCapacity and maxCapacity.
      */
     protected abstract ByteBuf newHeapBuffer(int initialCapacity, int maxCapacity);
 
     /**
      * Create a direct {@link ByteBuf} with the given initialCapacity and maxCapacity.
      */
     protected abstract ByteBuf newDirectBuffer(int initialCapacity, int maxCapacity);
 
     @Override
     public String toString() {
         return StringUtil.simpleClassName(this) + "(directByDefault: " + directByDefault + ')';
     }
 }