rev 12972 : 8140606: Update library code to use internal Unsafe
Reviewed-by: duke
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 sun.misc.Unsafe;
29
30 /**
31 * Factory for native buffers.
32 */
33
34 class NativeBuffers {
35 private NativeBuffers() { }
36
37 private static final Unsafe unsafe = Unsafe.getUnsafe();
38
39 private static final int TEMP_BUF_POOL_SIZE = 3;
40 private static ThreadLocal<NativeBuffer[]> threadLocal =
41 new ThreadLocal<NativeBuffer[]>();
42
43 /**
44 * Allocates a native buffer, of at least the given size, from the heap.
45 */
46 static NativeBuffer allocNativeBuffer(int size) {
47 // Make a new one of at least 2k
48 if (size < 2048) size = 2048;
49 return new NativeBuffer(size);
50 }
51
52 /**
53 * Returns a native buffer, of at least the given size, from the thread
54 * local cache.
55 */
56 static NativeBuffer getNativeBufferFromCache(int size) {
57 // return from cache if possible
58 NativeBuffer[] buffers = threadLocal.get();
59 if (buffers != null) {
60 for (int i=0; i<TEMP_BUF_POOL_SIZE; i++) {
61 NativeBuffer buffer = buffers[i];
62 if (buffer != null && buffer.size() >= size) {
63 buffers[i] = null;
64 return buffer;
65 }
66 }
67 }
68 return null;
69 }
70
71 /**
72 * Returns a native buffer, of at least the given size. The native buffer
73 * is taken from the thread local cache if possible; otherwise it is
74 * allocated from the heap.
75 */
76 static NativeBuffer getNativeBuffer(int size) {
77 NativeBuffer buffer = getNativeBufferFromCache(size);
78 if (buffer != null) {
79 buffer.setOwner(null);
80 return buffer;
81 } else {
82 return allocNativeBuffer(size);
83 }
84 }
85
86 /**
87 * Releases the given buffer. If there is space in the thread local cache
88 * then the buffer goes into the cache; otherwise the memory is deallocated.
89 */
90 static void releaseNativeBuffer(NativeBuffer buffer) {
91 // create cache if it doesn't exist
92 NativeBuffer[] buffers = threadLocal.get();
93 if (buffers == null) {
94 buffers = new NativeBuffer[TEMP_BUF_POOL_SIZE];
95 buffers[0] = buffer;
96 threadLocal.set(buffers);
97 return;
98 }
99 // Put it in an empty slot if such exists
100 for (int i=0; i<TEMP_BUF_POOL_SIZE; i++) {
101 if (buffers[i] == null) {
102 buffers[i] = buffer;
103 return;
104 }
105 }
106 // Otherwise replace a smaller one in the cache if such exists
107 for (int i=0; i<TEMP_BUF_POOL_SIZE; i++) {
108 NativeBuffer existing = buffers[i];
109 if (existing.size() < buffer.size()) {
110 existing.cleaner().clean();
111 buffers[i] = buffer;
112 return;
113 }
114 }
115
116 // free it
117 buffer.cleaner().clean();
118 }
119
120 /**
121 * Copies a byte array and zero terminator into a given native buffer.
122 */
123 static void copyCStringToNativeBuffer(byte[] cstr, NativeBuffer buffer) {
124 long offset = Unsafe.ARRAY_BYTE_BASE_OFFSET;
125 long len = cstr.length;
126 assert buffer.size() >= (len + 1);
127 unsafe.copyMemory(cstr, offset, null, buffer.address(), len);
128 unsafe.putByte(buffer.address() + len, (byte)0);
129 }
130
131 /**
132 * Copies a byte array and zero terminator into a native buffer, returning
133 * the buffer.
134 */
135 static NativeBuffer asNativeBuffer(byte[] cstr) {
136 NativeBuffer buffer = getNativeBuffer(cstr.length+1);
137 copyCStringToNativeBuffer(cstr, buffer);
138 return buffer;
139 }
140 }
--- EOF ---