1 /*
2 * Copyright (c) 2000, 2017, 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.ch;
27
28 import java.io.FileDescriptor;
29 import java.lang.reflect.Constructor;
30 import java.lang.reflect.InvocationTargetException;
31 import java.nio.ByteBuffer;
32 import java.nio.MappedByteBuffer;
33 import java.security.AccessController;
34 import java.security.PrivilegedAction;
35 import java.util.Collection;
36 import java.util.Iterator;
37 import java.util.Set;
38 import jdk.internal.misc.Unsafe;
39 import sun.security.action.GetPropertyAction;
40
41
42 public class Util {
43
44 // -- Caches --
45
46 // The number of temp buffers in our pool
47 private static final int TEMP_BUF_POOL_SIZE = IOUtil.IOV_MAX;
48
49 // The max size allowed for a cached temp buffer, in bytes
50 private static final long MAX_CACHED_BUFFER_SIZE = getMaxCachedBufferSize();
51
52 // Per-thread cache of temporary direct buffers
53 private static ThreadLocal<BufferCache> bufferCache =
54 new ThreadLocal<BufferCache>()
55 {
56 @Override
57 protected BufferCache initialValue() {
58 return new BufferCache();
59 }
60 };
61
62 /**
63 * Returns the max size allowed for a cached temp buffers, in
64 * bytes. It defaults to Long.MAX_VALUE. It can be set with the
65 * jdk.nio.maxCachedBufferSize property. Even though
66 * ByteBuffer.capacity() returns an int, we're using a long here
67 * for potential future-proofing.
68 */
69 private static long getMaxCachedBufferSize() {
70 String s = GetPropertyAction
71 .privilegedGetProperty("jdk.nio.maxCachedBufferSize");
72 if (s != null) {
73 try {
74 long m = Long.parseLong(s);
75 if (m >= 0) {
76 return m;
77 } else {
78 // if it's negative, ignore the system property
79 }
80 } catch (NumberFormatException e) {
81 // if the string is not well formed, ignore the system property
82 }
83 }
84 return Long.MAX_VALUE;
85 }
86
87 /**
88 * Returns true if a buffer of this size is too large to be
89 * added to the buffer cache, false otherwise.
90 */
91 private static boolean isBufferTooLarge(int size) {
92 return size > MAX_CACHED_BUFFER_SIZE;
93 }
94
95 /**
96 * Returns true if the buffer is too large to be added to the
97 * buffer cache, false otherwise.
98 */
99 private static boolean isBufferTooLarge(ByteBuffer buf) {
100 return isBufferTooLarge(buf.capacity());
101 }
102
103 /**
104 * A simple cache of direct buffers.
105 */
106 private static class BufferCache {
107 // the array of buffers
108 private ByteBuffer[] buffers;
109
110 // the number of buffers in the cache
111 private int count;
112
113 // the index of the first valid buffer (undefined if count == 0)
114 private int start;
115
116 private int next(int i) {
117 return (i + 1) % TEMP_BUF_POOL_SIZE;
118 }
119
120 BufferCache() {
121 buffers = new ByteBuffer[TEMP_BUF_POOL_SIZE];
122 }
123
124 /**
125 * Removes and returns a buffer from the cache of at least the given
126 * size (or null if no suitable buffer is found).
127 */
128 ByteBuffer get(int size) {
129 // Don't call this if the buffer would be too large.
130 assert !isBufferTooLarge(size);
131
132 if (count == 0)
133 return null; // cache is empty
134
135 ByteBuffer[] buffers = this.buffers;
136
137 // search for suitable buffer (often the first buffer will do)
138 ByteBuffer buf = buffers[start];
139 if (buf.capacity() < size) {
140 buf = null;
141 int i = start;
142 while ((i = next(i)) != start) {
143 ByteBuffer bb = buffers[i];
144 if (bb == null)
145 break;
146 if (bb.capacity() >= size) {
147 buf = bb;
148 break;
149 }
150 }
151 if (buf == null)
152 return null;
153 // move first element to here to avoid re-packing
154 buffers[i] = buffers[start];
155 }
156
157 // remove first element
158 buffers[start] = null;
159 start = next(start);
160 count--;
161
162 // prepare the buffer and return it
163 buf.rewind();
164 buf.limit(size);
165 return buf;
166 }
167
168 boolean offerFirst(ByteBuffer buf) {
169 // Don't call this if the buffer is too large.
170 assert !isBufferTooLarge(buf);
171
172 if (count >= TEMP_BUF_POOL_SIZE) {
173 return false;
174 } else {
175 start = (start + TEMP_BUF_POOL_SIZE - 1) % TEMP_BUF_POOL_SIZE;
176 buffers[start] = buf;
177 count++;
178 return true;
179 }
180 }
181
182 boolean offerLast(ByteBuffer buf) {
183 // Don't call this if the buffer is too large.
184 assert !isBufferTooLarge(buf);
185
186 if (count >= TEMP_BUF_POOL_SIZE) {
187 return false;
188 } else {
189 int next = (start + count) % TEMP_BUF_POOL_SIZE;
190 buffers[next] = buf;
191 count++;
192 return true;
193 }
194 }
195
196 boolean isEmpty() {
197 return count == 0;
198 }
199
200 ByteBuffer removeFirst() {
201 assert count > 0;
202 ByteBuffer buf = buffers[start];
203 buffers[start] = null;
204 start = next(start);
205 count--;
206 return buf;
207 }
208 }
209
210 /**
211 * Returns a temporary buffer of at least the given size
212 */
213 public static ByteBuffer getTemporaryDirectBuffer(int size) {
214 // If a buffer of this size is too large for the cache, there
215 // should not be a buffer in the cache that is at least as
216 // large. So we'll just create a new one. Also, we don't have
217 // to remove the buffer from the cache (as this method does
218 // below) given that we won't put the new buffer in the cache.
219 if (isBufferTooLarge(size)) {
220 return ByteBuffer.allocateDirect(size);
221 }
222
223 BufferCache cache = bufferCache.get();
224 ByteBuffer buf = cache.get(size);
225 if (buf != null) {
226 return buf;
227 } else {
228 // No suitable buffer in the cache so we need to allocate a new
229 // one. To avoid the cache growing then we remove the first
230 // buffer from the cache and free it.
231 if (!cache.isEmpty()) {
232 buf = cache.removeFirst();
233 free(buf);
234 }
235 return ByteBuffer.allocateDirect(size);
236 }
237 }
238
239 /**
240 * Releases a temporary buffer by returning to the cache or freeing it.
241 */
242 public static void releaseTemporaryDirectBuffer(ByteBuffer buf) {
243 offerFirstTemporaryDirectBuffer(buf);
244 }
245
246 /**
247 * Releases a temporary buffer by returning to the cache or freeing it. If
248 * returning to the cache then insert it at the start so that it is
249 * likely to be returned by a subsequent call to getTemporaryDirectBuffer.
250 */
251 static void offerFirstTemporaryDirectBuffer(ByteBuffer buf) {
252 // If the buffer is too large for the cache we don't have to
253 // check the cache. We'll just free it.
254 if (isBufferTooLarge(buf)) {
255 free(buf);
256 return;
257 }
258
259 assert buf != null;
260 BufferCache cache = bufferCache.get();
261 if (!cache.offerFirst(buf)) {
262 // cache is full
263 free(buf);
264 }
265 }
266
267 /**
268 * Releases a temporary buffer by returning to the cache or freeing it. If
269 * returning to the cache then insert it at the end. This makes it
270 * suitable for scatter/gather operations where the buffers are returned to
271 * cache in same order that they were obtained.
272 */
273 static void offerLastTemporaryDirectBuffer(ByteBuffer buf) {
274 // If the buffer is too large for the cache we don't have to
275 // check the cache. We'll just free it.
276 if (isBufferTooLarge(buf)) {
277 free(buf);
278 return;
279 }
280
281 assert buf != null;
282 BufferCache cache = bufferCache.get();
283 if (!cache.offerLast(buf)) {
284 // cache is full
285 free(buf);
286 }
287 }
288
289 /**
290 * Frees the memory for the given direct buffer
291 */
292 private static void free(ByteBuffer buf) {
293 ((DirectBuffer)buf).cleaner().clean();
294 }
295
296
297 // -- Random stuff --
298
299 static ByteBuffer[] subsequence(ByteBuffer[] bs, int offset, int length) {
300 if ((offset == 0) && (length == bs.length))
301 return bs;
302 int n = length;
303 ByteBuffer[] bs2 = new ByteBuffer[n];
304 for (int i = 0; i < n; i++)
305 bs2[i] = bs[offset + i];
306 return bs2;
307 }
308
309 static <E> Set<E> ungrowableSet(final Set<E> s) {
310 return new Set<E>() {
311
312 public int size() { return s.size(); }
313 public boolean isEmpty() { return s.isEmpty(); }
314 public boolean contains(Object o) { return s.contains(o); }
315 public Object[] toArray() { return s.toArray(); }
316 public <T> T[] toArray(T[] a) { return s.toArray(a); }
317 public String toString() { return s.toString(); }
318 public Iterator<E> iterator() { return s.iterator(); }
319 public boolean equals(Object o) { return s.equals(o); }
320 public int hashCode() { return s.hashCode(); }
321 public void clear() { s.clear(); }
322 public boolean remove(Object o) { return s.remove(o); }
323
324 public boolean containsAll(Collection<?> coll) {
325 return s.containsAll(coll);
326 }
327 public boolean removeAll(Collection<?> coll) {
328 return s.removeAll(coll);
329 }
330 public boolean retainAll(Collection<?> coll) {
331 return s.retainAll(coll);
332 }
333
334 public boolean add(E o){
335 throw new UnsupportedOperationException();
336 }
337 public boolean addAll(Collection<? extends E> coll) {
338 throw new UnsupportedOperationException();
339 }
340
341 };
342 }
343
344
345 // -- Unsafe access --
346
347 private static Unsafe unsafe = Unsafe.getUnsafe();
348
349 private static byte _get(long a) {
350 return unsafe.getByte(a);
351 }
352
353 private static void _put(long a, byte b) {
354 unsafe.putByte(a, b);
355 }
356
357 static void erase(ByteBuffer bb) {
358 unsafe.setMemory(((DirectBuffer)bb).address(), bb.capacity(), (byte)0);
359 }
360
361 static Unsafe unsafe() {
362 return unsafe;
363 }
364
365 private static int pageSize = -1;
366
367 static int pageSize() {
368 if (pageSize == -1)
369 pageSize = unsafe().pageSize();
370 return pageSize;
371 }
372
373 private static volatile Constructor<?> directByteBufferConstructor;
374
375 private static void initDBBConstructor() {
376 AccessController.doPrivileged(new PrivilegedAction<Void>() {
377 public Void run() {
378 try {
379 Class<?> cl = Class.forName("java.nio.DirectByteBuffer");
380 Constructor<?> ctor = cl.getDeclaredConstructor(
381 new Class<?>[] { int.class,
382 long.class,
383 FileDescriptor.class,
384 Runnable.class });
385 ctor.setAccessible(true);
386 directByteBufferConstructor = ctor;
387 } catch (ClassNotFoundException |
388 NoSuchMethodException |
389 IllegalArgumentException |
390 ClassCastException x) {
391 throw new InternalError(x);
392 }
393 return null;
394 }});
395 }
396
397 static MappedByteBuffer newMappedByteBuffer(int size, long addr,
398 FileDescriptor fd,
399 Runnable unmapper)
400 {
401 MappedByteBuffer dbb;
402 if (directByteBufferConstructor == null)
403 initDBBConstructor();
404 try {
405 dbb = (MappedByteBuffer)directByteBufferConstructor.newInstance(
406 new Object[] { size,
407 addr,
408 fd,
409 unmapper });
410 } catch (InstantiationException |
411 IllegalAccessException |
412 InvocationTargetException e) {
413 throw new InternalError(e);
414 }
415 return dbb;
416 }
417
418 private static volatile Constructor<?> directByteBufferRConstructor;
419
420 private static void initDBBRConstructor() {
421 AccessController.doPrivileged(new PrivilegedAction<Void>() {
422 public Void run() {
423 try {
424 Class<?> cl = Class.forName("java.nio.DirectByteBufferR");
425 Constructor<?> ctor = cl.getDeclaredConstructor(
426 new Class<?>[] { int.class,
427 long.class,
428 FileDescriptor.class,
429 Runnable.class });
430 ctor.setAccessible(true);
431 directByteBufferRConstructor = ctor;
432 } catch (ClassNotFoundException |
433 NoSuchMethodException |
434 IllegalArgumentException |
435 ClassCastException x) {
436 throw new InternalError(x);
437 }
438 return null;
439 }});
440 }
441
442 static MappedByteBuffer newMappedByteBufferR(int size, long addr,
443 FileDescriptor fd,
444 Runnable unmapper)
445 {
446 MappedByteBuffer dbb;
447 if (directByteBufferRConstructor == null)
448 initDBBRConstructor();
449 try {
450 dbb = (MappedByteBuffer)directByteBufferRConstructor.newInstance(
451 new Object[] { size,
452 addr,
453 fd,
454 unmapper });
455 } catch (InstantiationException |
456 IllegalAccessException |
457 InvocationTargetException e) {
458 throw new InternalError(e);
459 }
460 return dbb;
461 }
462 }