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/*
* Copyright (C) 2012 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.providers.contacts;
import android.content.Context;
import android.content.SharedPreferences;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.provider.ContactsContract.ContactCounts;
import android.text.TextUtils;
import android.util.Log;
import com.google.android.collect.Maps;
import com.google.common.annotations.VisibleForTesting;
import java.util.Map;
import java.util.regex.Pattern;
/**
* Cache for the "fast scrolling index".
*
* It's a cache from "keys" and "bundles" (see {@link #mCache} for what they are). The cache
* content is also persisted in the shared preferences, so it'll survive even if the process
* is killed or the device reboots.
*
* All the content will be invalidated when the provider detects an operation that could potentially
* change the index.
*
* There's no maximum number for cached entries. It's okay because we store keys and values in
* a compact form in both the in-memory cache and the preferences. Also the query in question
* (the query for contact lists) has relatively low number of variations.
*
* This class is thread-safe.
*/
public class FastScrollingIndexCache {
private static final String TAG = "LetterCountCache";
@VisibleForTesting
static final String PREFERENCE_KEY = "LetterCountCache";
/**
* Separator used for in-memory structure.
*/
private static final String SEPARATOR = "\u0001";
private static final Pattern SEPARATOR_PATTERN = Pattern.compile(SEPARATOR);
/**
* Separator used for serializing values for preferences.
*/
private static final String SAVE_SEPARATOR = "\u0002";
private static final Pattern SAVE_SEPARATOR_PATTERN = Pattern.compile(SAVE_SEPARATOR);
private final SharedPreferences mPrefs;
private boolean mPreferenceLoaded;
/**
* In-memory cache.
*
* It's essentially a map from keys, which are query parameters passed to {@link #get}, to
* values, which are {@link Bundle}s that will be appended to a {@link Cursor} as extras.
*
* However, in order to save memory, we store stringified keys and values in the cache.
* Key strings are generated by {@link #buildCacheKey} and values are generated by
* {@link #buildCacheValue}.
*
* We store those strings joined with {@link #SAVE_SEPARATOR} as the separator when saving
* to shared preferences.
*/
private final Map<String, String> mCache = Maps.newHashMap();
public FastScrollingIndexCache(Context context) {
this(PreferenceManager.getDefaultSharedPreferences(context));
// At this point, the SharedPreferences might just have been generated and may still be
// loading from the file, in which case loading from the preferences would be blocked.
// To avoid that, we load lazily.
}
@VisibleForTesting
FastScrollingIndexCache(SharedPreferences prefs) {
mPrefs = prefs;
}
/**
* Append a {@link String} to a {@link StringBuilder}.
*
* Unlike the original {@link StringBuilder#append}, it does *not* append the string "null" if
* {@code value} is null.
*/
private static void appendIfNotNull(StringBuilder sb, Object value) {
if (value != null) {
sb.append(value.toString());
}
}
private static String buildCacheKey(Uri queryUri, String selection, String[] selectionArgs,
String sortOrder, String countExpression) {
final StringBuilder sb = new StringBuilder();
appendIfNotNull(sb, queryUri);
appendIfNotNull(sb, SEPARATOR);
appendIfNotNull(sb, selection);
appendIfNotNull(sb, SEPARATOR);
appendIfNotNull(sb, sortOrder);
appendIfNotNull(sb, SEPARATOR);
appendIfNotNull(sb, countExpression);
if (selectionArgs != null) {
for (int i = 0; i < selectionArgs.length; i++) {
appendIfNotNull(sb, SEPARATOR);
appendIfNotNull(sb, selectionArgs[i]);
}
}
return sb.toString();
}
@VisibleForTesting
static String buildCacheValue(String[] titles, int[] counts) {
final StringBuilder sb = new StringBuilder();
for (int i = 0; i < titles.length; i++) {
if (i > 0) {
appendIfNotNull(sb, SEPARATOR);
}
appendIfNotNull(sb, titles[i]);
appendIfNotNull(sb, SEPARATOR);
appendIfNotNull(sb, Integer.toString(counts[i]));
}
return sb.toString();
}
/**
* Creates and returns a {@link Bundle} that is appended to a {@link Cursor} as extras.
*/
public static final Bundle buildExtraBundle(String[] titles, int[] counts) {
Bundle bundle = new Bundle();
bundle.putStringArray(ContactCounts.EXTRA_ADDRESS_BOOK_INDEX_TITLES, titles);
bundle.putIntArray(ContactCounts.EXTRA_ADDRESS_BOOK_INDEX_COUNTS, counts);
return bundle;
}
@VisibleForTesting
static Bundle buildExtraBundleFromValue(String value) {
final String[] values;
if (TextUtils.isEmpty(value)) {
values = new String[0];
} else {
values = SEPARATOR_PATTERN.split(value);
}
if ((values.length) % 2 != 0) {
return null; // malformed
}
try {
final int numTitles = values.length / 2;
final String[] titles = new String[numTitles];
final int[] counts = new int[numTitles];
for (int i = 0; i < numTitles; i++) {
titles[i] = values[i * 2];
counts[i] = Integer.parseInt(values[i * 2 + 1]);
}
return buildExtraBundle(titles, counts);
} catch (RuntimeException e) {
Log.w(TAG, "Failed to parse cached value", e);
return null; // malformed
}
}
public Bundle get(Uri queryUri, String selection, String[] selectionArgs, String sortOrder,
String countExpression) {
synchronized (mCache) {
ensureLoaded();
final String key = buildCacheKey(queryUri, selection, selectionArgs, sortOrder,
countExpression);
final String value = mCache.get(key);
if (value == null) {
if (Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG, "Miss: " + key);
}
return null;
}
final Bundle b = buildExtraBundleFromValue(value);
if (b == null) {
// Value was malformed for whatever reason.
mCache.remove(key);
save();
} else {
if (Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG, "Hit: " + key);
}
}
return b;
}
}
/**
* Put a {@link Bundle} into the cache. {@link Bundle} MUST be built with
* {@link #buildExtraBundle(String[], int[])}.
*/
public void put(Uri queryUri, String selection, String[] selectionArgs, String sortOrder,
String countExpression, Bundle bundle) {
synchronized (mCache) {
ensureLoaded();
final String key = buildCacheKey(queryUri, selection, selectionArgs, sortOrder,
countExpression);
mCache.put(key, buildCacheValue(
bundle.getStringArray(ContactCounts.EXTRA_ADDRESS_BOOK_INDEX_TITLES),
bundle.getIntArray(ContactCounts.EXTRA_ADDRESS_BOOK_INDEX_COUNTS)));
save();
if (Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG, "Put: " + key);
}
}
}
public void invalidate() {
synchronized (mCache) {
mPrefs.edit().remove(PREFERENCE_KEY).apply();
mCache.clear();
mPreferenceLoaded = true;
if (Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG, "Invalidated");
}
}
}
/**
* Store the cache to the preferences.
*
* We concatenate all key+value pairs into one string and save it.
*/
private void save() {
final StringBuilder sb = new StringBuilder();
for (String key : mCache.keySet()) {
if (sb.length() > 0) {
appendIfNotNull(sb, SAVE_SEPARATOR);
}
appendIfNotNull(sb, key);
appendIfNotNull(sb, SAVE_SEPARATOR);
appendIfNotNull(sb, mCache.get(key));
}
mPrefs.edit().putString(PREFERENCE_KEY, sb.toString()).apply();
}
private void ensureLoaded() {
if (mPreferenceLoaded) return;
if (Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG, "Loading...");
}
// Even when we fail to load, don't retry loading again.
mPreferenceLoaded = true;
boolean successfullyLoaded = false;
try {
final String savedValue = mPrefs.getString(PREFERENCE_KEY, null);
if (!TextUtils.isEmpty(savedValue)) {
final String[] keysAndValues = SAVE_SEPARATOR_PATTERN.split(savedValue);
if ((keysAndValues.length % 2) != 0) {
return; // malformed
}
for (int i = 1; i < keysAndValues.length; i += 2) {
final String key = keysAndValues[i - 1];
final String value = keysAndValues[i];
if (Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG, "Loaded: " + key);
}
mCache.put(key, value);
}
}
successfullyLoaded = true;
} catch (RuntimeException e) {
Log.w(TAG, "Failed to load from preferences", e);
// But don't crash apps!
} finally {
if (!successfullyLoaded) {
invalidate();
}
}
}
}
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