| /* |
| * Copyright 2000-2011 JetBrains s.r.o. |
| * |
| * 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.intellij.openapi.editor.impl; |
| |
| import java.util.concurrent.atomic.AtomicLong; |
| |
| /** |
| * Low-contention counter. |
| * Repeated calls to {@link #next()} return numbers which are unique across all calling threads, and which are increasing over calls within one thread. |
| */ |
| public class StripedIDGenerator { |
| private static final int CHUNK_SIZE = 1000; |
| private final AtomicLong nextChunkStart = new AtomicLong(); |
| // must not be static since we might want to have several instances of this class |
| private final ThreadLocal<NextPair> localCounter = new ThreadLocal<NextPair>(); |
| private static class NextPair { |
| long nextId; |
| final long limit; |
| |
| private NextPair(long nextId, long limit) { |
| this.nextId = nextId; |
| this.limit = limit; |
| } |
| } |
| |
| public long next() { |
| NextPair nextPair = localCounter.get(); |
| if (nextPair == null || nextPair.nextId == nextPair.limit) { |
| long start = nextChunkStart.getAndAdd(CHUNK_SIZE); |
| nextPair = new NextPair(start, start + CHUNK_SIZE); |
| localCounter.set(nextPair); |
| } |
| long result = nextPair.nextId; |
| nextPair.nextId++; |
| return result; |
| } |
| } |