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   /*
    * Copyright 2015 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.epoll;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.ByteBufAllocator;
  import io.netty.channel.RecvByteBufAllocator.DelegatingHandle;
  import io.netty.channel.RecvByteBufAllocator.ExtendedHandle;
  import io.netty.channel.unix.PreferredDirectByteBufAllocator;
  import io.netty.util.UncheckedBooleanSupplier;
  
  class EpollRecvByteAllocatorHandle extends DelegatingHandle implements ExtendedHandle {
      private final PreferredDirectByteBufAllocator preferredDirectByteBufAllocator =
              new PreferredDirectByteBufAllocator();
      private final UncheckedBooleanSupplier defaultMaybeMoreDataSupplier = new UncheckedBooleanSupplier() {
          @Override
          public boolean get() {
              return maybeMoreDataToRead();
          }
      };
      private boolean isEdgeTriggered;
      private boolean receivedRdHup;
  
      EpollRecvByteAllocatorHandle(ExtendedHandle handle) {
          super(handle);
      }
  
      final void receivedRdHup() {
          receivedRdHup = true;
      }
  
      final boolean isReceivedRdHup() {
          return receivedRdHup;
      }
  
      boolean maybeMoreDataToRead() {
          /**
           * EPOLL ET requires that we read until we get an EAGAIN
           * (see Q9 in <a href="https://man7.org/linux/man-pages/man7/epoll.7.html">epoll man</a>). However in order to
           * respect auto read we supporting reading to stop if auto read is off. It is expected that the
           * {@link #EpollSocketChannel} implementations will track if we are in edgeTriggered mode and all data was not
           * read, and will force a EPOLLIN ready event.
           *
           * It is assumed RDHUP is handled externally by checking {@link #isReceivedRdHup()}.
           */
          return (isEdgeTriggered && lastBytesRead() > 0) ||
                 (!isEdgeTriggered && lastBytesRead() == attemptedBytesRead());
      }
  
      final void edgeTriggered(boolean edgeTriggered) {
          isEdgeTriggered = edgeTriggered;
      }
  
      final boolean isEdgeTriggered() {
          return isEdgeTriggered;
      }
  
      @Override
      public final ByteBuf allocate(ByteBufAllocator alloc) {
          // We need to ensure we always allocate a direct ByteBuf as we can only use a direct buffer to read via JNI.
          preferredDirectByteBufAllocator.updateAllocator(alloc);
          return delegate().allocate(preferredDirectByteBufAllocator);
      }
  
      @Override
      public final boolean continueReading(UncheckedBooleanSupplier maybeMoreDataSupplier) {
          return ((ExtendedHandle) delegate()).continueReading(maybeMoreDataSupplier);
      }
  
      @Override
      public final boolean continueReading() {
          // We must override the supplier which determines if there maybe more data to read.
          return continueReading(defaultMaybeMoreDataSupplier);
      }
  }