org.whispersystems.textsecuregcm.limits.LeakyBucket.java Source code

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Here is the source code for org.whispersystems.textsecuregcm.limits.LeakyBucket.java

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/**
 * Copyright (C) 2013 Open WhisperSystems
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.whispersystems.textsecuregcm.limits;

import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

import java.io.IOException;

public class LeakyBucket {

    private final int bucketSize;
    private final double leakRatePerMillis;

    private int spaceRemaining;
    private long lastUpdateTimeMillis;

    public LeakyBucket(int bucketSize, double leakRatePerMillis) {
        this(bucketSize, leakRatePerMillis, bucketSize, System.currentTimeMillis());
    }

    private LeakyBucket(int bucketSize, double leakRatePerMillis, int spaceRemaining, long lastUpdateTimeMillis) {
        this.bucketSize = bucketSize;
        this.leakRatePerMillis = leakRatePerMillis;
        this.spaceRemaining = spaceRemaining;
        this.lastUpdateTimeMillis = lastUpdateTimeMillis;
    }

    public boolean add(int amount) {
        this.spaceRemaining = getUpdatedSpaceRemaining();
        this.lastUpdateTimeMillis = System.currentTimeMillis();

        if (this.spaceRemaining >= amount) {
            this.spaceRemaining -= amount;
            return true;
        } else {
            return false;
        }
    }

    private int getUpdatedSpaceRemaining() {
        long elapsedTime = System.currentTimeMillis() - this.lastUpdateTimeMillis;

        return Math.min(this.bucketSize,
                (int) Math.floor(this.spaceRemaining + (elapsedTime * this.leakRatePerMillis)));
    }

    public String serialize(ObjectMapper mapper) throws JsonProcessingException {
        return mapper.writeValueAsString(
                new LeakyBucketEntity(bucketSize, leakRatePerMillis, spaceRemaining, lastUpdateTimeMillis));
    }

    public static LeakyBucket fromSerialized(ObjectMapper mapper, String serialized) throws IOException {
        LeakyBucketEntity entity = mapper.readValue(serialized, LeakyBucketEntity.class);

        return new LeakyBucket(entity.bucketSize, entity.leakRatePerMillis, entity.spaceRemaining,
                entity.lastUpdateTimeMillis);
    }

    private static class LeakyBucketEntity {
        @JsonProperty
        private int bucketSize;

        @JsonProperty
        private double leakRatePerMillis;

        @JsonProperty
        private int spaceRemaining;

        @JsonProperty
        private long lastUpdateTimeMillis;

        public LeakyBucketEntity() {
        }

        private LeakyBucketEntity(int bucketSize, double leakRatePerMillis, int spaceRemaining,
                long lastUpdateTimeMillis) {
            this.bucketSize = bucketSize;
            this.leakRatePerMillis = leakRatePerMillis;
            this.spaceRemaining = spaceRemaining;
            this.lastUpdateTimeMillis = lastUpdateTimeMillis;
        }
    }
}