67 lines
2.4 KiB
Java
67 lines
2.4 KiB
Java
/*
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* SPDX-License-Identifier: MIT
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*
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* The MIT License (MIT)
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*
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* Copyright (c) 2015-2021 <Your name and contributors>
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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package com.github.games647.fastlogin.core;
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/**
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* Limit the number of requests with a maximum size. Each requests expires after the specified time making it available
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* for another request.
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*/
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public class RateLimiter {
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private final long[] requests;
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private final long expireTime;
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private int position;
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public RateLimiter(int maxLimit, long expireTime) {
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this.requests = new long[maxLimit];
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this.expireTime = expireTime;
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}
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/**
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* Ask if access is allowed. If so register the request.
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*
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* @return true if allowed - false otherwise without any side effects
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*/
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public boolean tryAcquire() {
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// current time millis is not monotonic - it can jump back depending on user choice or NTP
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long now = System.nanoTime() / 1_000_000;
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// after this the request should be expired
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long toBeExpired = now - expireTime;
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synchronized (this) {
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// having synchronized will limit the amount of concurrency a lot
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long oldest = requests[position];
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if (oldest < toBeExpired) {
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requests[position] = now;
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position = (position + 1) % requests.length;
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return true;
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}
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return false;
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}
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}
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}
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