Author: atm
Date: Thu Jan 3 19:20:52 2013
New Revision: 1428560
URL: http://svn.apache.org/viewvc?rev=1428560&view=rev
Log:
Add file which was accidentally missed during commit of HDFS-4346.
Added:
hadoop/common/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/SequentialNumber.java
Added:
hadoop/common/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/SequentialNumber.java
URL:
http://svn.apache.org/viewvc/hadoop/common/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/SequentialNumber.java?rev=1428560&view=auto
==============================================================================
---
hadoop/common/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/SequentialNumber.java
(added)
+++
hadoop/common/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/SequentialNumber.java
Thu Jan 3 19:20:52 2013
@@ -0,0 +1,83 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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 org.apache.hadoop.util;
+
+import java.util.concurrent.atomic.AtomicLong;
+
+import org.apache.hadoop.classification.InterfaceAudience;
+
+/**
+ * Sequential number generator.
+ *
+ * This class is thread safe.
+ */
[email protected]
+public abstract class SequentialNumber {
+ private final AtomicLong currentValue;
+
+ /** Create a new instance with the given initial value. */
+ protected SequentialNumber(final long initialValue) {
+ currentValue = new AtomicLong(initialValue);
+ }
+
+ /** @return the current value. */
+ public long getCurrentValue() {
+ return currentValue.get();
+ }
+
+ /** Set current value. */
+ public void setCurrentValue(long value) {
+ currentValue.set(value);
+ }
+
+ /** Increment and then return the next value. */
+ public long nextValue() {
+ return currentValue.incrementAndGet();
+ }
+
+ /** Skip to the new value. */
+ public void skipTo(long newValue) throws IllegalStateException {
+ for(;;) {
+ final long c = getCurrentValue();
+ if (newValue < c) {
+ throw new IllegalStateException(
+ "Cannot skip to less than the current value (="
+ + c + "), where newValue=" + newValue);
+ }
+
+ if (currentValue.compareAndSet(c, newValue)) {
+ return;
+ }
+ }
+ }
+
+ @Override
+ public boolean equals(final Object that) {
+ if (that == null || this.getClass() != that.getClass()) {
+ return false;
+ }
+ final AtomicLong thatValue = ((SequentialNumber)that).currentValue;
+ return currentValue.equals(thatValue);
+ }
+
+ @Override
+ public int hashCode() {
+ final long v = currentValue.get();
+ return (int)v ^ (int)(v >>> 32);
+ }
+}
