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+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef _ANDROID_NIO_UTILS_H_
+#define _ANDROID_NIO_UTILS_H_
+
+#include <jni.h>
+
+#include <cstddef>
+
+namespace android {
+
+/**
+ * Class providing scoped access to the memory backing a java.nio.Buffer instance.
+ *
+ * Instances of this class should only be allocated on the stack as heap allocation is not
+ * supported.
+ *
+ * Instances of this class do not create any global references for performance reasons.
+ */
+class AutoBufferPointer final {
+public:
+ /** Constructor for an AutoBufferPointer instance.
+ *
+ * @param env The current JNI env
+ * @param nioBuffer Instance of a java.nio.Buffer whose memory will be accessed.
+ * @param commit JNI_TRUE if the underlying memory will be updated and should be
+ * copied back to the managed heap. JNI_FALSE if the data will
+ * not be modified or the modifications may be discarded.
+ *
+ * The commit parameter is only applicable if the buffer is backed by a managed heap
+ * array and the runtime had to provide a copy of the data rather than the original data.
+ */
+ AutoBufferPointer(JNIEnv* env, jobject nioBuffer, jboolean commit);
+
+ /** Destructor for an AutoBufferPointer instance.
+ *
+ * Releases critical managed heap array pointer if acquired.
+ */
+ ~AutoBufferPointer();
+
+ /**
+ * Returns a pointer to the current position of the buffer provided to the constructor. This
+ * pointer is only valid whilst the AutoBufferPointer instance remains in scope.
+ */
+ void* pointer() const { return fPointer; }
+
+private:
+ JNIEnv* const fEnv;
+ void* fPointer; // Pointer to current buffer position when constructed.
+ void* fElements; // Pointer to array element 0 (null if buffer is direct, may be
+ // within fArray or point to a copy of the array).
+ jarray fArray; // Pointer to array on managed heap.
+ const jboolean fCommit; // Flag to commit data to source (when fElements is a copy of fArray).
+
+ // Unsupported constructors and operators.
+ AutoBufferPointer() = delete;
+ AutoBufferPointer(AutoBufferPointer&) = delete;
+ AutoBufferPointer& operator=(AutoBufferPointer&) = delete;
+ static void* operator new(size_t);
+ static void* operator new[](size_t);
+ static void* operator new(size_t, void*);
+ static void* operator new[](size_t, void*);
+ static void operator delete(void*, size_t);
+ static void operator delete[](void*, size_t);
+};
+
+} /* namespace android */
+
+#endif // _ANDROID_NIO_UTILS_H_