63 lines
2.0 KiB
Java
63 lines
2.0 KiB
Java
/*
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* Copyright (C) 2020 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.android.internal.logging;
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import static java.lang.Math.max;
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import static java.lang.Math.min;
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import com.android.internal.annotations.VisibleForTesting;
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import java.security.SecureRandom;
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import java.util.Random;
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/**
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* Generates random InstanceIds in range [1, instanceIdMax] for passing to
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* UiEventLogger.logWithInstanceId(). Holds a SecureRandom, which self-seeds on
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* first use; try to give it a long lifetime. Safe for concurrent use.
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*/
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public class InstanceIdSequence {
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protected final int mInstanceIdMax;
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private final Random mRandom = new SecureRandom();
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/**
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* Constructs a sequence with identifiers [1, instanceIdMax]. Capped at INSTANCE_ID_MAX.
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* @param instanceIdMax Limiting value of identifiers. Normally positive: otherwise you get
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* an all-1 sequence.
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*/
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public InstanceIdSequence(int instanceIdMax) {
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mInstanceIdMax = min(max(1, instanceIdMax), InstanceId.INSTANCE_ID_MAX);
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}
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/**
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* Gets the next instance from the sequence. Safe for concurrent use.
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* @return new InstanceId
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*/
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public InstanceId newInstanceId() {
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return newInstanceIdInternal(1 + mRandom.nextInt(mInstanceIdMax));
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}
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/**
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* Factory function for instance IDs, used for testing.
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* @param id
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* @return new InstanceId(id)
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*/
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@VisibleForTesting
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protected InstanceId newInstanceIdInternal(int id) {
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return new InstanceId(id);
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}
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}
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