1 /*
2 * Copyright 2016 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.channel;
17
18 import io.netty.util.IntSupplier;
19
20 /**
21 * Select strategy interface.
22 *
23 * Provides the ability to control the behavior of the select loop. For example a blocking select
24 * operation can be delayed or skipped entirely if there are events to process immediately.
25 */
26 public interface SelectStrategy {
27
28 /**
29 * Indicates a blocking select should follow.
30 */
31 int SELECT = -1;
32 /**
33 * Indicates the IO loop should be retried, no blocking select to follow directly.
34 */
35 int CONTINUE = -2;
36 /**
37 * Indicates the IO loop to poll for new events without blocking.
38 */
39 int BUSY_WAIT = -3;
40
41 /**
42 * The {@link SelectStrategy} can be used to steer the outcome of a potential select
43 * call.
44 *
45 * @param selectSupplier The supplier with the result of a select result.
46 * @param hasTasks true if tasks are waiting to be processed.
47 * @return {@link #SELECT} if the next step should be blocking select {@link #CONTINUE} if
48 * the next step should be to not select but rather jump back to the IO loop and try
49 * again. Any value >= 0 is treated as an indicator that work needs to be done.
50 */
51 int calculateStrategy(IntSupplier selectSupplier, boolean hasTasks) throws Exception;
52 }