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
17package com.android.volley;
18
19/**
20 * An interface for a cache keyed by a String with a byte array as data.
21 */
22public interface Cache {
23    /**
24     * Retrieves an entry from the cache.
25     * @param key Cache key
26     * @return An {@link Entry} or null in the event of a cache miss
27     */
28    public Entry get(String key);
29
30    /**
31     * Adds or replaces an entry to the cache.
32     * @param key Cache key
33     * @param entry Data to store and metadata for cache coherency, TTL, etc.
34     */
35    public void put(String key, Entry entry);
36
37    /**
38     * Performs any potentially long-running actions needed to initialize the cache;
39     * will be called from a worker thread.
40     */
41    public void initialize();
42
43    /**
44     * Invalidates an entry in the cache.
45     * @param key Cache key
46     * @param fullExpire True to fully expire the entry, false to soft expire
47     */
48    public void invalidate(String key, boolean fullExpire);
49
50    /**
51     * Removes an entry from the cache.
52     * @param key Cache key
53     */
54    public void remove(String key);
55
56    /**
57     * Empties the cache.
58     */
59    public void clear();
60
61    /**
62     * Data and metadata for an entry returned by the cache.
63     */
64    public static class Entry {
65        /** The data returned from cache. */
66        public byte[] data;
67
68        /** ETag for cache coherency. */
69        public String etag;
70
71        /** Date of this response as reported by the server. */
72        public long serverDate;
73
74        /** TTL for this record. */
75        public long ttl;
76
77        /** Soft TTL for this record. */
78        public long softTtl;
79
80        /** True if the entry is expired. */
81        public boolean isExpired() {
82            return this.ttl < System.currentTimeMillis();
83        }
84
85        /** True if a refresh is needed from the original data source. */
86        public boolean refreshNeeded() {
87            return this.softTtl < System.currentTimeMillis();
88        }
89    }
90
91}
92