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/*
* Copyright (C) 2011 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.android.volley;
import java.util.Collections;
import java.util.List;
import java.util.Map;
/** An interface for a cache keyed by a String with a byte array as data. */
public interface Cache {
/**
* Retrieves an entry from the cache.
*
* @param key Cache key
* @return An {@link Entry} or null in the event of a cache miss
*/
Entry get(String key);
/**
* Adds or replaces an entry to the cache.
*
* @param key Cache key
* @param entry Data to store and metadata for cache coherency, TTL, etc.
*/
void put(String key, Entry entry);
/**
* Performs any potentially long-running actions needed to initialize the cache; will be called
* from a worker thread.
*/
void initialize();
/**
* Invalidates an entry in the cache.
*
* @param key Cache key
* @param fullExpire True to fully expire the entry, false to soft expire
*/
void invalidate(String key, boolean fullExpire);
/**
* Removes an entry from the cache.
*
* @param key Cache key
*/
void remove(String key);
/** Empties the cache. */
void clear();
/** Data and metadata for an entry returned by the cache. */
class Entry {
/** The data returned from cache. */
public byte[] data;
/** ETag for cache coherency. */
public String etag;
/** Date of this response as reported by the server. */
public long serverDate;
/** The last modified date for the requested object. */
public long lastModified;
/** TTL for this record. */
public long ttl;
/** Soft TTL for this record. */
public long softTtl;
/**
* Response headers as received from server; must be non-null. Should not be mutated
* directly.
*
* <p>Note that if the server returns two headers with the same (case-insensitive) name,
* this map will only contain the one of them. {@link #allResponseHeaders} may contain all
* headers if the {@link Cache} implementation supports it.
*/
public Map<String, String> responseHeaders = Collections.emptyMap();
/**
* All response headers. May be null depending on the {@link Cache} implementation. Should
* not be mutated directly.
*/
public List<Header> allResponseHeaders;
/** True if the entry is expired. */
public boolean isExpired() {
return this.ttl < System.currentTimeMillis();
}
/** True if a refresh is needed from the original data source. */
public boolean refreshNeeded() {
return this.softTtl < System.currentTimeMillis();
}
}
}
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