src/com/android/providers/contacts/FastScrollingIndexCache.java - platform/packages/providers/ContactsProvider - Git at Google

 /*
  * 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.Contacts;
 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();

     private static FastScrollingIndexCache sSingleton;

     public static FastScrollingIndexCache getInstance(Context context) {
         if (sSingleton == null) {
             SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
             sSingleton = new FastScrollingIndexCache(prefs);
         }
         return sSingleton;
     }

     @VisibleForTesting
     static synchronized FastScrollingIndexCache getInstanceForTest(
             SharedPreferences prefs) {
         sSingleton = new FastScrollingIndexCache(prefs);
         return sSingleton;
     }

     private 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(Contacts.EXTRA_ADDRESS_BOOK_INDEX_TITLES, titles);
         bundle.putIntArray(Contacts.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(Contacts.EXTRA_ADDRESS_BOOK_INDEX_TITLES),
                     bundle.getIntArray(Contacts.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).commit();
             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();
             }
         }
     }
 }
	/*
	* 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.Contacts;
	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();

	private static FastScrollingIndexCache sSingleton;

	public static FastScrollingIndexCache getInstance(Context context) {
	if (sSingleton == null) {
	SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
	sSingleton = new FastScrollingIndexCache(prefs);
	}
	return sSingleton;
	}

	@VisibleForTesting
	static synchronized FastScrollingIndexCache getInstanceForTest(
	SharedPreferences prefs) {
	sSingleton = new FastScrollingIndexCache(prefs);
	return sSingleton;
	}

	private 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(Contacts.EXTRA_ADDRESS_BOOK_INDEX_TITLES, titles);
	bundle.putIntArray(Contacts.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(Contacts.EXTRA_ADDRESS_BOOK_INDEX_TITLES),
	bundle.getIntArray(Contacts.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).commit();
	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();
	}
	}
	}
	}