1 /* Licensed to the Apache Software Foundation (ASF) under one or more 2 * contributor license agreements. See the NOTICE file distributed with 3 * this work for additional information regarding copyright ownership. 4 * The ASF licenses this file to You under the Apache License, Version 2.0 5 * (the "License"); you may not use this file except in compliance with 6 * the License. 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 java.io.FileDescriptor; 20 import java.nio.channels.FileChannel; 21 22 /** 23 * @hide internal use only 24 */ 25 public final class NioUtils { NioUtils()26 private NioUtils() { 27 } 28 29 /** 30 * Gets the start address of a direct buffer. 31 * <p> 32 * This method corresponds to the JNI function: 33 * 34 * <pre> 35 * void* GetDirectBufferAddress(JNIEnv* env, jobject buf); 36 * </pre> 37 * 38 * @param buf 39 * the direct buffer whose address shall be returned must not be 40 * <code>null</code>. 41 * @return the address of the buffer given, or zero if the buffer is not a 42 * direct Buffer. 43 */ getDirectBufferAddress(Buffer buffer)44 public static int getDirectBufferAddress(Buffer buffer) { 45 return buffer.effectiveDirectAddress; 46 } 47 freeDirectBuffer(ByteBuffer buffer)48 public static void freeDirectBuffer(ByteBuffer buffer) { 49 if (buffer == null) { 50 return; 51 } 52 if (buffer instanceof DirectByteBuffer) { 53 ((DirectByteBuffer) buffer).free(); 54 } else if (buffer instanceof MappedByteBuffer) { 55 ((MappedByteBufferAdapter) buffer).free(); 56 } else { 57 throw new AssertionError(); 58 } 59 } 60 61 /** 62 * Returns the int file descriptor from within the given FileChannel 'fc'. 63 */ getFD(FileChannel fc)64 public static FileDescriptor getFD(FileChannel fc) { 65 return ((FileChannelImpl) fc).getFD(); 66 } 67 68 /** 69 * Helps bridge between io and nio. 70 */ newFileChannel(Object stream, FileDescriptor fd, int mode)71 public static FileChannel newFileChannel(Object stream, FileDescriptor fd, int mode) { 72 return new FileChannelImpl(stream, fd, mode); 73 } 74 75 /** 76 * Exposes the array backing a non-direct ByteBuffer, even if the ByteBuffer is read-only. 77 * Normally, attempting to access the array backing a read-only buffer throws. 78 */ unsafeArray(ByteBuffer b)79 public static byte[] unsafeArray(ByteBuffer b) { 80 return ((HeapByteBuffer) b).backingArray; 81 } 82 83 /** 84 * Exposes the array offset for the array backing a non-direct ByteBuffer, 85 * even if the ByteBuffer is read-only. 86 */ unsafeArrayOffset(ByteBuffer b)87 public static int unsafeArrayOffset(ByteBuffer b) { 88 return ((HeapByteBuffer) b).offset; 89 } 90 } 91