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      1 /*
      2  * Copyright (C) 2010 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.view;
     18 
     19 import android.os.Parcel;
     20 import android.os.Parcelable;
     21 import android.util.Slog;
     22 
     23 /**
     24  * An input channel specifies the file descriptors used to send input events to
     25  * a window in another process.  It is Parcelable so that it can be sent
     26  * to the process that is to receive events.  Only one thread should be reading
     27  * from an InputChannel at a time.
     28  * @hide
     29  */
     30 public final class InputChannel implements Parcelable {
     31     private static final String TAG = "InputChannel";
     32 
     33     private static final boolean DEBUG = false;
     34 
     35     public static final Parcelable.Creator<InputChannel> CREATOR
     36             = new Parcelable.Creator<InputChannel>() {
     37         public InputChannel createFromParcel(Parcel source) {
     38             InputChannel result = new InputChannel();
     39             result.readFromParcel(source);
     40             return result;
     41         }
     42 
     43         public InputChannel[] newArray(int size) {
     44             return new InputChannel[size];
     45         }
     46     };
     47 
     48     @SuppressWarnings("unused")
     49     private int mPtr; // used by native code
     50 
     51     private boolean mDisposeAfterWriteToParcel;
     52 
     53     private static native InputChannel[] nativeOpenInputChannelPair(String name);
     54 
     55     private native void nativeDispose(boolean finalized);
     56     private native void nativeTransferTo(InputChannel other);
     57     private native void nativeReadFromParcel(Parcel parcel);
     58     private native void nativeWriteToParcel(Parcel parcel);
     59 
     60     private native String nativeGetName();
     61 
     62     /**
     63      * Creates an uninitialized input channel.
     64      * It can be initialized by reading from a Parcel or by transferring the state of
     65      * another input channel into this one.
     66      */
     67     public InputChannel() {
     68     }
     69 
     70     @Override
     71     protected void finalize() throws Throwable {
     72         try {
     73             nativeDispose(true);
     74         } finally {
     75             super.finalize();
     76         }
     77     }
     78 
     79     /**
     80      * Creates a new input channel pair.  One channel should be provided to the input
     81      * dispatcher and the other to the application's input queue.
     82      * @param name The descriptive (non-unique) name of the channel pair.
     83      * @return A pair of input channels.  They are symmetric and indistinguishable.
     84      */
     85     public static InputChannel[] openInputChannelPair(String name) {
     86         if (name == null) {
     87             throw new IllegalArgumentException("name must not be null");
     88         }
     89 
     90         if (DEBUG) {
     91             Slog.d(TAG, "Opening input channel pair '" + name + "'");
     92         }
     93         return nativeOpenInputChannelPair(name);
     94     }
     95 
     96     /**
     97      * Gets the name of the input channel.
     98      * @return The input channel name.
     99      */
    100     public String getName() {
    101         String name = nativeGetName();
    102         return name != null ? name : "uninitialized";
    103     }
    104 
    105     /**
    106      * Disposes the input channel.
    107      * Explicitly releases the reference this object is holding on the input channel.
    108      * When all references are released, the input channel will be closed.
    109      */
    110     public void dispose() {
    111         nativeDispose(false);
    112     }
    113 
    114     /**
    115      * Transfers ownership of the internal state of the input channel to another
    116      * instance and invalidates this instance.  This is used to pass an input channel
    117      * as an out parameter in a binder call.
    118      * @param other The other input channel instance.
    119      */
    120     public void transferToBinderOutParameter(InputChannel outParameter) {
    121         if (outParameter == null) {
    122             throw new IllegalArgumentException("outParameter must not be null");
    123         }
    124 
    125         nativeTransferTo(outParameter);
    126         outParameter.mDisposeAfterWriteToParcel = true;
    127     }
    128 
    129     public int describeContents() {
    130         return Parcelable.CONTENTS_FILE_DESCRIPTOR;
    131     }
    132 
    133     public void readFromParcel(Parcel in) {
    134         if (in == null) {
    135             throw new IllegalArgumentException("in must not be null");
    136         }
    137 
    138         nativeReadFromParcel(in);
    139     }
    140 
    141     public void writeToParcel(Parcel out, int flags) {
    142         if (out == null) {
    143             throw new IllegalArgumentException("out must not be null");
    144         }
    145 
    146         nativeWriteToParcel(out);
    147 
    148         if (mDisposeAfterWriteToParcel) {
    149             dispose();
    150         }
    151     }
    152 
    153     @Override
    154     public String toString() {
    155         return getName();
    156     }
    157 }
    158