1 /*
2  * Copyright (C) 2007 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 java.nio;
18 
19 import static android.annotation.SystemApi.Client.MODULE_LIBRARIES;
20 
21 import android.annotation.SystemApi;
22 
23 import android.compat.annotation.UnsupportedAppUsage;
24 
25 /**
26  * This class is used via JNI by code in frameworks/base/ and
27  * by the JniConstants cache in libnativehelper/.
28  * @hide
29  */
30 // @VisibleForTesting : was default
31 @SystemApi(client = MODULE_LIBRARIES)
32 public final class NIOAccess {
33 
NIOAccess()34     private NIOAccess() {}
35 
36     /**
37      * Returns the underlying native pointer to the data of the given
38      * Buffer starting at the Buffer's current position, or 0 if the
39      * Buffer is not backed by native heap storage.
40      * @hide
41      */
42     // @VisibleForTesting : was default
43     @UnsupportedAppUsage
getBasePointer(Buffer b)44     public static long getBasePointer(Buffer b) {
45         long address = b.address;
46         if (address == 0L) {
47             return 0L;
48         }
49         return address + (b.position << b._elementSizeShift);
50     }
51 
52     /**
53      * Returns the underlying Java array containing the data of the
54      * given Buffer, or null if the Buffer is not backed by a Java array.
55      *
56      * @param b  {@code Buffer} to get its underlying data array
57      * @return   underlying Java array
58      *
59      * @hide
60      */
61     @UnsupportedAppUsage
62     @SystemApi(client = MODULE_LIBRARIES)
getBaseArray(Buffer b)63     public static Object getBaseArray(Buffer b) {
64         return b.hasArray() ? b.array() : null;
65     }
66 
67     /**
68      * Returns the offset in bytes from the start of the underlying
69      * Java array object containing the data of the given Buffer to
70      * the actual start of the data. The start of the data takes into
71      * account the Buffer's current position. This method is only
72      * meaningful if {@link #getBaseArray(Buffer)} returns non-null.
73      *
74      * @param b {@code Buffer} to get its underlying data array's base offset
75      * @return  underlying Java array's base offset
76      *
77      * @hide
78      */
79     @UnsupportedAppUsage
80     @SystemApi(client = MODULE_LIBRARIES)
getBaseArrayOffset(Buffer b)81     public static int getBaseArrayOffset(Buffer b) {
82         return b.hasArray() ? ((b.arrayOffset() + b.position) << b._elementSizeShift) : 0;
83     }
84 }
85