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      1 /*
      2  * Copyright (C) 2011 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package android.system;
     18 
     19 import java.io.FileDescriptor;
     20 import libcore.util.Objects;
     21 
     22 /**
     23  * Used as an in/out parameter to {@link Os#poll}.
     24  * Corresponds to C's {@code struct pollfd} from {@code <poll.h>}.
     25  */
     26 public final class StructPollfd {
     27   /** The file descriptor to poll. */
     28   public FileDescriptor fd;
     29 
     30   /**
     31    * The events we're interested in. POLLIN corresponds to being in select(2)'s read fd set,
     32    * POLLOUT to the write fd set.
     33    */
     34   public short events;
     35 
     36   /** The events that actually happened. */
     37   public short revents;
     38 
     39   /**
     40    * A non-standard extension that lets callers conveniently map back to the object
     41    * their fd belongs to. This is used by Selector, for example, to associate each
     42    * FileDescriptor with the corresponding SelectionKey.
     43    */
     44   public Object userData;
     45 
     46   @Override public String toString() {
     47     return Objects.toString(this);
     48   }
     49 }
     50