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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 static native InputChannel[] nativeOpenInputChannelPair(String name);
     52 
     53     private native void nativeDispose(boolean finalized);
     54     private native void nativeTransferTo(InputChannel other);
     55     private native void nativeReadFromParcel(Parcel parcel);
     56     private native void nativeWriteToParcel(Parcel parcel);
     57 
     58     private native String nativeGetName();
     59 
     60     /**
     61      * Creates an uninitialized input channel.
     62      * It can be initialized by reading from a Parcel or by transferring the state of
     63      * another input channel into this one.
     64      */
     65     public InputChannel() {
     66     }
     67 
     68     @Override
     69     protected void finalize() throws Throwable {
     70         try {
     71             nativeDispose(true);
     72         } finally {
     73             super.finalize();
     74         }
     75     }
     76 
     77     /**
     78      * Creates a new input channel pair.  One channel should be provided to the input
     79      * dispatcher and the other to the application's input queue.
     80      * @param name The descriptive (non-unique) name of the channel pair.
     81      * @return A pair of input channels.  They are symmetric and indistinguishable.
     82      */
     83     public static InputChannel[] openInputChannelPair(String name) {
     84         if (name == null) {
     85             throw new IllegalArgumentException("name must not be null");
     86         }
     87 
     88         if (DEBUG) {
     89             Slog.d(TAG, "Opening input channel pair '" + name + "'");
     90         }
     91         return nativeOpenInputChannelPair(name);
     92     }
     93 
     94     /**
     95      * Gets the name of the input channel.
     96      * @return The input channel name.
     97      */
     98     public String getName() {
     99         String name = nativeGetName();
    100         return name != null ? name : "uninitialized";
    101     }
    102 
    103     /**
    104      * Disposes the input channel.
    105      * Explicitly releases the reference this object is holding on the input channel.
    106      * When all references are released, the input channel will be closed.
    107      */
    108     public void dispose() {
    109         nativeDispose(false);
    110     }
    111 
    112     /**
    113      * Transfers ownership of the internal state of the input channel to another
    114      * instance and invalidates this instance.  This is used to pass an input channel
    115      * as an out parameter in a binder call.
    116      * @param other The other input channel instance.
    117      */
    118     public void transferTo(InputChannel outParameter) {
    119         if (outParameter == null) {
    120             throw new IllegalArgumentException("outParameter must not be null");
    121         }
    122 
    123         nativeTransferTo(outParameter);
    124     }
    125 
    126     public int describeContents() {
    127         return Parcelable.CONTENTS_FILE_DESCRIPTOR;
    128     }
    129 
    130     public void readFromParcel(Parcel in) {
    131         if (in == null) {
    132             throw new IllegalArgumentException("in must not be null");
    133         }
    134 
    135         nativeReadFromParcel(in);
    136     }
    137 
    138     public void writeToParcel(Parcel out, int flags) {
    139         if (out == null) {
    140             throw new IllegalArgumentException("out must not be null");
    141         }
    142 
    143         nativeWriteToParcel(out);
    144 
    145         if ((flags & PARCELABLE_WRITE_RETURN_VALUE) != 0) {
    146             dispose();
    147         }
    148     }
    149 
    150     @Override
    151     public String toString() {
    152         return getName();
    153     }
    154 }
    155