1 /*
2 * ====================================================================
3 * Licensed to the Apache Software Foundation (ASF) under one
4 * or more contributor license agreements. See the NOTICE file
5 * distributed with this work for additional information
6 * regarding copyright ownership. The ASF licenses this file
7 * to you under the Apache License, Version 2.0 (the
8 * "License"); you may not use this file except in compliance
9 * with the License. You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing,
14 * software distributed under the License is distributed on an
15 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
16 * KIND, either express or implied. See the License for the
17 * specific language governing permissions and limitations
18 * under the License.
19 * ====================================================================
20 *
21 * This software consists of voluntary contributions made by many
22 * individuals on behalf of the Apache Software Foundation. For more
23 * information on the Apache Software Foundation, please see
24 * <http://www.apache.org/>.
25 *
26 */
27 package org.apache.hc.core5.http.nio;
28
29 import java.io.IOException;
30
31 /**
32 * Abstract asynchronous data producer.
33 *
34 * @since 5.0
35 */
36 public interface AsyncDataProducer extends ResourceHolder {
37
38 /**
39 * Returns the number of bytes immediately available for output.
40 * This method can be used as a hint to control output events
41 * of the underlying I/O session.
42 * <p>
43 * Please note this method should return zero if the data producer
44 * is unable to produce any more data, in which case
45 * {@link #produce(DataStreamChannel)} method will not get triggered.
46 * The producer can resume writing out data asynchronously
47 * once more data becomes available or request output readiness events
48 * with {@link DataStreamChannel#requestOutput()}.
49 *
50 * @return the number of bytes immediately available for output
51 *
52 * @see #produce(DataStreamChannel)
53 * @see DataStreamChannel#requestOutput()
54 */
55 int available();
56
57 /**
58 * Triggered to signal the ability of the underlying data channel
59 * to accept more data. The data producer can choose to write data
60 * immediately inside the call or asynchronously at some later point.
61 * <p>
62 * Please note this method gets triggered only if {@link #available()}
63 * returns a positive value.
64 *
65 * @param channel the data channel capable of accepting more data.
66 * @throws IOException in case of an I/O error.
67 * @see #available()
68 */
69 void produce(DataStreamChannel channel) throws IOException;
70
71 }