1 /*
2  * Copyright (C) 2008 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 #ifndef _ANDROID_NIO_UTILS_H_
18 #define _ANDROID_NIO_UTILS_H_
19 
20 #include <android_runtime/AndroidRuntime.h>
21 
22 namespace android {
23 
24 /**
25  * Given an nio.Buffer, return a pointer to it, beginning at its current
26  * position. The returned pointer is only valid for the current JNI stack-frame.
27  * For performance, it does not create any global references, so the getPointer
28  * (and releasePointer if array is returned non-null) must be done in the
29  * same JNI stack-frame.
30  *
31  * @param env   The current JNI env
32  * @param buffer    The nio.Buffer object
33  * @param array     REQUIRED. Output. If on return it is set to non-null, then
34  *                  nio_releasePointer must be called with the array
35  *                  and the returned pointer when the caller is through with it.
36  *                  If on return it is set to null, do not call
37  *                  nio_releasePointer.
38  * @return The pointer to the memory in the buffer object
39  */
40 void* nio_getPointer(JNIEnv *env, jobject buffer, jarray *array);
41 
42 /**
43  * Call this if android_nio_getPointer returned non-null in its array parameter.
44  * Pass that array and the returned pointer when you are done accessing the
45  * pointer. If called (i.e. array is non-null), it must be called in the same
46  * JNI stack-frame as getPointer
47  *
48  * @param env   The current JNI env
49  * @param buffer    The array returned from android_nio_getPointer (!= null)
50  * @param pointer   The pointer returned by android_nio_getPointer
51  * @param commit    JNI_FALSE if the pointer was just read, and JNI_TRUE if
52  *                  the pointer was written to.
53  */
54 void nio_releasePointer(JNIEnv *env, jarray array, void *pointer,
55                                 jboolean commit);
56 
57 class AutoBufferPointer {
58 public:
59     AutoBufferPointer(JNIEnv* env, jobject nioBuffer, jboolean commit);
60     ~AutoBufferPointer();
61 
pointer()62     void* pointer() const { return fPointer; }
63 
64 private:
65     JNIEnv* fEnv;
66     void*   fPointer;
67     jarray  fArray;
68     jboolean fCommit;
69 };
70 
71 }   /* namespace android */
72 
73 #endif  // _ANDROID_NIO_UTILS_H_
74