1 /* 2 * Copyright (c) 2008, 2009, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package sun.nio.fs; 27 28 import jdk.internal.misc.JavaLangAccess; 29 import jdk.internal.misc.SharedSecrets; 30 import jdk.internal.misc.Unsafe; 31 32 /** 33 * Factory for native buffers. 34 */ 35 36 class NativeBuffers { 37 private static JavaLangAccess JLA = SharedSecrets.getJavaLangAccess(); 38 39 private static final Unsafe unsafe = Unsafe.getUnsafe(); 40 41 private static final int TEMP_BUF_POOL_SIZE = 3; 42 private static ThreadLocal<NativeBuffer[]> threadLocal = 43 new ThreadLocal<NativeBuffer[]>(); 44 45 private NativeBuffers() { } 46 47 /** 48 * Allocates a native buffer, of at least the given size, from the heap. 49 */ 50 static NativeBuffer allocNativeBuffer(int size) { 51 // Make a new one of at least 2k 52 if (size < 2048) size = 2048; 53 return new NativeBuffer(size); 54 } 55 56 /** 57 * Returns a native buffer, of at least the given size, from the thread 58 * local cache. 59 */ 60 static NativeBuffer getNativeBufferFromCache(int size) { 61 // return from cache if possible 62 NativeBuffer[] buffers = JLA.getKernelThreadLocal(threadLocal); 63 if (buffers != null) { 64 for (int i=0; i<TEMP_BUF_POOL_SIZE; i++) { 65 NativeBuffer buffer = buffers[i]; 66 if (buffer != null && buffer.size() >= size) { 67 buffers[i] = null; 68 return buffer; 69 } 70 } 71 } 72 return null; 73 } 74 75 /** 76 * Returns a native buffer, of at least the given size. The native buffer 77 * is taken from the thread local cache if possible; otherwise it is 78 * allocated from the heap. 79 */ 80 static NativeBuffer getNativeBuffer(int size) { 81 NativeBuffer buffer = getNativeBufferFromCache(size); 82 if (buffer != null) { 83 buffer.setOwner(null); 84 return buffer; 85 } else { 86 return allocNativeBuffer(size); 87 } 88 } 89 90 /** 91 * Releases the given buffer. If there is space in the thread local cache 92 * then the buffer goes into the cache; otherwise the memory is deallocated. 93 */ 94 static void releaseNativeBuffer(NativeBuffer buffer) { 95 // create cache if it doesn't exist 96 NativeBuffer[] buffers = JLA.getKernelThreadLocal(threadLocal); 97 if (buffers == null) { 98 buffers = new NativeBuffer[TEMP_BUF_POOL_SIZE]; 99 buffers[0] = buffer; 100 threadLocal.set(buffers); 101 return; 102 } 103 // Put it in an empty slot if such exists 104 for (int i=0; i<TEMP_BUF_POOL_SIZE; i++) { 105 if (buffers[i] == null) { 106 buffers[i] = buffer; 107 return; 108 } 109 } 110 // Otherwise replace a smaller one in the cache if such exists 111 for (int i=0; i<TEMP_BUF_POOL_SIZE; i++) { 112 NativeBuffer existing = buffers[i]; 113 if (existing.size() < buffer.size()) { 114 existing.free(); 115 buffers[i] = buffer; 116 return; 117 } 118 } 119 120 // free it 121 buffer.free(); 122 } 123 124 /** 125 * Copies a byte array and zero terminator into a given native buffer. 126 */ 127 static void copyCStringToNativeBuffer(byte[] cstr, NativeBuffer buffer) { 128 long offset = Unsafe.ARRAY_BYTE_BASE_OFFSET; 129 long len = cstr.length; 130 assert buffer.size() >= (len + 1); 131 unsafe.copyMemory(cstr, offset, null, buffer.address(), len); 132 unsafe.putByte(buffer.address() + len, (byte)0); 133 } 134 135 /** 136 * Copies a byte array and zero terminator into a native buffer, returning 137 * the buffer. 138 */ 139 static NativeBuffer asNativeBuffer(byte[] cstr) { 140 NativeBuffer buffer = getNativeBuffer(cstr.length+1); 141 copyCStringToNativeBuffer(cstr, buffer); 142 return buffer; 143 } 144 }