1/*
2 * Copyright (C) 2011 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://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,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17
18package android.filterfw.core;
19
20import java.util.Set;
21
22import android.filterfw.core.Filter;
23import android.filterfw.core.Scheduler;
24
25/**
26 * @hide
27 */
28public class RoundRobinScheduler extends Scheduler {
29
30    private int mLastPos = -1;
31
32    public RoundRobinScheduler(FilterGraph graph) {
33        super(graph);
34    }
35
36    @Override
37    public void reset() {
38        mLastPos = -1;
39    }
40
41    @Override
42    public Filter scheduleNextNode() {
43        Set<Filter> all_filters = getGraph().getFilters();
44        if (mLastPos >= all_filters.size()) mLastPos = -1;
45        int pos = 0;
46        Filter first = null;
47        int firstNdx = -1;
48        for (Filter filter : all_filters) {
49            if (filter.canProcess()) {
50                if (pos <= mLastPos) {
51                    if (first == null) {
52                        // store the first available filter
53                        first = filter;
54                        firstNdx = pos;
55                    }
56                } else {
57                    // return the next available filter since last
58                    mLastPos = pos;
59                    return filter;
60                }
61            }
62            pos ++;
63        }
64        // going around from the beginning
65        if (first != null ) {
66            mLastPos = firstNdx;
67            return first;
68        }
69        // if there is nothing to be scheduled, still keep the previous
70        // position.
71        return null;
72    }
73}
74