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/*
* Copyright (C) 2022 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.net.module.util;
import android.util.SparseIntArray;
import com.android.internal.annotations.GuardedBy;
import com.android.internal.annotations.VisibleForTesting;
/**
* Keeps track of the counters under different uid, fire exception if the counter
* exceeded the specified maximum value.
*
* @hide
*/
public class PerUidCounter {
private final int mMaxCountPerUid;
// Map from UID to count that UID has filed.
@VisibleForTesting
@GuardedBy("this")
final SparseIntArray mUidToCount = new SparseIntArray();
/**
* Constructor
*
* @param maxCountPerUid the maximum count per uid allowed
*/
public PerUidCounter(final int maxCountPerUid) {
if (maxCountPerUid <= 0) {
throw new IllegalArgumentException("Maximum counter value must be positive");
}
mMaxCountPerUid = maxCountPerUid;
}
/**
* Increments the count of the given uid. Throws an exception if the number
* of the counter for the uid exceeds the value of maxCounterPerUid which is the value
* passed into the constructor. see: {@link #PerUidCounter(int)}.
*
* @throws IllegalStateException if the number of counter for the uid exceed
* the allowed number.
*
* @param uid the uid that the counter was made under
*/
public synchronized void incrementCountOrThrow(final int uid) {
final long newCount = ((long) mUidToCount.get(uid, 0)) + 1;
if (newCount > mMaxCountPerUid) {
throw new IllegalStateException("Uid " + uid + " exceeded its allowed limit");
}
// Since the count cannot be greater than Integer.MAX_VALUE here since mMaxCountPerUid
// is an integer, it is safe to cast to int.
mUidToCount.put(uid, (int) newCount);
}
/**
* Decrements the count of the given uid. Throws an exception if the number
* of the counter goes below zero.
*
* @throws IllegalStateException if the number of counter for the uid goes below
* zero.
*
* @param uid the uid that the count was made under
*/
public synchronized void decrementCountOrThrow(final int uid) {
final int newCount = mUidToCount.get(uid, 0) - 1;
if (newCount < 0) {
throw new IllegalStateException("BUG: too small count " + newCount + " for UID " + uid);
} else if (newCount == 0) {
mUidToCount.delete(uid);
} else {
mUidToCount.put(uid, newCount);
}
}
@VisibleForTesting
public synchronized int get(int uid) {
return mUidToCount.get(uid, 0);
}
}
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