1 /*
2 * Copyright 2017 The Netty Project
3 *
4 * The Netty Project licenses this file to you under the Apache License,
5 * version 2.0 (the "License"); you may not use this file except in compliance
6 * with the License. You may obtain a copy of the License at:
7 *
8 * https://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, WITHOUT
12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13 * License for the specific language governing permissions and limitations
14 * under the License.
15 */
16 package io.netty.util.internal;
17
18 import java.nio.ByteBuffer;
19
20 /**
21 * Allows to free direct {@link ByteBuffer}s.
22 */
23 interface Cleaner {
24 /**
25 * Create a direct {@link ByteBuffer} and return it alongside its cleaning mechanism,
26 * in a {@link CleanableDirectBuffer}.
27 *
28 * @param capacity The desired capacity of the direct buffer.
29 * @return The new {@link CleanableDirectBuffer} instance.
30 */
31 CleanableDirectBuffer allocate(int capacity);
32
33 /**
34 * Reallocate a direct buffer with a new capacity. The old buffer is consumed and
35 * must not be used after this call.
36 * <p>
37 * The default implementation allocates a new buffer, copies the data, and frees the old one.
38 * Implementations may override this to provide more efficient reallocation (e.g. via
39 * {@code Unsafe.reallocateMemory}).
40 */
41 default CleanableDirectBuffer reallocate(CleanableDirectBuffer old, int newCapacity) {
42 CleanableDirectBuffer newBuf = allocate(newCapacity);
43 ByteBuffer oldBB = old.buffer();
44 ByteBuffer newBB = newBuf.buffer();
45 int bytesToCopy = Math.min(oldBB.capacity(), newCapacity);
46 oldBB.position(0).limit(bytesToCopy);
47 newBB.position(0).limit(bytesToCopy);
48 newBB.put(oldBB).clear();
49 old.clean();
50 return newBuf;
51 }
52
53 /**
54 * Free a direct {@link ByteBuffer} if possible
55 *
56 * @deprecated Instead allocate buffers from {@link #allocate(int)}
57 * and use the associated {@link CleanableDirectBuffer#clean()} method.
58 */
59 @Deprecated
60 void freeDirectBuffer(ByteBuffer buffer);
61
62 /**
63 * Check if the clean operation is "relatively expensive".
64 * Expensive clean operations are fine for pooling allocators, but should be avoided for unpooled buffers.
65 * @return {@code true} if this Cleaner has an expensive clean
66 * (i.e. {@link CleanableDirectBuffer#clean()}) operation.
67 */
68 boolean hasExpensiveClean();
69 }