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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.inputmethod.research;
import android.util.Log;
import com.android.inputmethod.latin.Dictionary;
import com.android.inputmethod.latin.Suggest;
import com.android.inputmethod.latin.define.ProductionFlag;
import java.util.Random;
public class MainLogBuffer extends LogBuffer {
private static final String TAG = MainLogBuffer.class.getSimpleName();
private static final boolean DEBUG = false && ProductionFlag.IS_EXPERIMENTAL_DEBUG;
// The size of the n-grams logged. E.g. N_GRAM_SIZE = 2 means to sample bigrams.
private static final int N_GRAM_SIZE = 2;
// The number of words between n-grams to omit from the log.
private static final int DEFAULT_NUMBER_OF_WORDS_BETWEEN_SAMPLES =
ProductionFlag.IS_EXPERIMENTAL_DEBUG ? 2 : 18;
private final ResearchLog mResearchLog;
private Suggest mSuggest;
// The minimum periodicity with which n-grams can be sampled. E.g. mWinWordPeriod is 10 if
// every 10th bigram is sampled, i.e., words 1-8 are not, but the bigram at words 9 and 10, etc.
// for 11-18, and the bigram at words 19 and 20. If an n-gram is not safe (e.g. it contains a
// number in the middle or an out-of-vocabulary word), then sampling is delayed until a safe
// n-gram does appear.
/* package for test */ int mMinWordPeriod;
// Counter for words left to suppress before an n-gram can be sampled. Reset to mMinWordPeriod
// after a sample is taken.
/* package for test */ int mWordsUntilSafeToSample;
public MainLogBuffer(final ResearchLog researchLog) {
super(N_GRAM_SIZE);
mResearchLog = researchLog;
mMinWordPeriod = DEFAULT_NUMBER_OF_WORDS_BETWEEN_SAMPLES + N_GRAM_SIZE;
final Random random = new Random();
mWordsUntilSafeToSample = random.nextInt(mMinWordPeriod);
}
public void setSuggest(Suggest suggest) {
mSuggest = suggest;
}
@Override
public void shiftIn(final LogUnit newLogUnit) {
super.shiftIn(newLogUnit);
if (newLogUnit.hasWord()) {
if (mWordsUntilSafeToSample > 0) {
mWordsUntilSafeToSample--;
}
}
if (DEBUG) {
Log.d(TAG, "shiftedIn " + (newLogUnit.hasWord() ? newLogUnit.getWord() : ""));
}
}
public void resetWordCounter() {
mWordsUntilSafeToSample = mMinWordPeriod;
}
/**
* Determines whether the content of the MainLogBuffer can be safely uploaded in its complete
* form and still protect the user's privacy.
*
* The size of the MainLogBuffer is just enough to hold one n-gram, its corrections, and any
* non-character data that is typed between words. The decision about privacy is made based on
* the buffer's entire content. If it is decided that the privacy risks are too great to upload
* the contents of this buffer, a censored version of the LogItems may still be uploaded. E.g.,
* the screen orientation and other characteristics about the device can be uploaded without
* revealing much about the user.
*/
public boolean isSafeToLog() {
// Check that we are not sampling too frequently. Having sampled recently might disclose
// too much of the user's intended meaning.
if (mWordsUntilSafeToSample > 0) {
return false;
}
if (mSuggest == null || !mSuggest.hasMainDictionary()) {
// Main dictionary is unavailable. Since we cannot check it, we cannot tell if a word
// is out-of-vocabulary or not. Therefore, we must judge the entire buffer contents to
// potentially pose a privacy risk.
return false;
}
// Reload the dictionary in case it has changed (e.g., because the user has changed
// languages).
final Dictionary dictionary = mSuggest.getMainDictionary();
if (dictionary == null) {
return false;
}
// Check each word in the buffer. If any word poses a privacy threat, we cannot upload the
// complete buffer contents in detail.
final int length = mLogUnits.size();
for (int i = 0; i < length; i++) {
final LogUnit logUnit = mLogUnits.get(i);
final String word = logUnit.getWord();
if (word == null) {
// Digits outside words are a privacy threat.
if (logUnit.mayContainDigit()) {
return false;
}
} else {
// Words not in the dictionary are a privacy threat.
if (ResearchLogger.hasLetters(word) && !(dictionary.isValidWord(word))) {
if (DEBUG) {
Log.d(TAG, "NOT SAFE!: hasLetters: " + ResearchLogger.hasLetters(word)
+ ", isValid: " + (dictionary.isValidWord(word)));
}
return false;
}
}
}
// All checks have passed; this buffer's content can be safely uploaded.
return true;
}
@Override
protected void onShiftOut(LogUnit logUnit) {
if (mResearchLog != null) {
mResearchLog.publish(logUnit, false /* isIncludingPrivateData */);
}
}
}
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