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   /*
    * Copyright 2017 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.unix;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.util.internal.PlatformDependent;
  
  import java.net.InetAddress;
  import java.net.InetSocketAddress;
  import java.net.UnknownHostException;
  
  import static io.netty.channel.unix.Limits.IOV_MAX;
  
  public final class UnixChannelUtil {
  
      private UnixChannelUtil() {
      }
  
      /**
       * Checks if the specified buffer has memory address or is composed of n(n <= IOV_MAX) NIO direct buffers.
       * (We check this because otherwise we need to make it a new direct buffer.)
       */
      public static boolean isBufferCopyNeededForWrite(ByteBuf byteBuf) {
          return isBufferCopyNeededForWrite(byteBuf, IOV_MAX);
      }
  
      static boolean isBufferCopyNeededForWrite(ByteBuf byteBuf, int iovMax) {
          return !byteBuf.hasMemoryAddress() && (!byteBuf.isDirect() || byteBuf.nioBufferCount() > iovMax);
      }
  
      public static InetSocketAddress computeRemoteAddr(InetSocketAddress remoteAddr, InetSocketAddress osRemoteAddr) {
          if (osRemoteAddr != null) {
              if (PlatformDependent.javaVersion() >= 7) {
                  try {
                      // Only try to construct a new InetSocketAddress if we using java >= 7 as getHostString() does not
                      // exists in earlier releases and so the retrieval of the hostname could block the EventLoop if a
                      // reverse lookup would be needed.
                      return new InetSocketAddress(InetAddress.getByAddress(remoteAddr.getHostString(),
                              osRemoteAddr.getAddress().getAddress()),
                              osRemoteAddr.getPort());
                  } catch (UnknownHostException ignore) {
                      // Should never happen but fallback to osRemoteAddr anyway.
                  }
              }
              return osRemoteAddr;
          }
          return remoteAddr;
      }
  }