Home | History | Annotate | Download | only in jni 
      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 
     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