HADOOP-2345. New HDFS transactions to support appending

to files.  Disk layout version changed from -11 to -12. (dhruba)



git-svn-id: https://svn.apache.org/repos/asf/hadoop/core/trunk@627665 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/hadoop/dfs/GenerationStamp.java

@@ -0,0 +1,111 @@
+/**
+ * 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.dfs;
+
+import java.io.*;
+import org.apache.hadoop.io.*;
+
+/****************************************************************
+ * A GenerationStamp is a Hadoop FS primitive, identified by a long.
+ ****************************************************************/
+class GenerationStamp implements WritableComparable {
+
+  static {                                      // register a ctor
+    WritableFactories.setFactory
+      (GenerationStamp.class,
+       new WritableFactory() {
+         public Writable newInstance() { return new GenerationStamp(); }
+       });
+  }
+
+  long genstamp;
+
+  /**
+   * Create a new instance, initialized to 0.
+   */
+  public GenerationStamp() {
+    this.genstamp = 0;
+  }
+
+  /**
+   * Create a new instance, initialized to the specified value.
+   */
+  public GenerationStamp(long stamp) {
+    this.genstamp = stamp;
+  }
+
+  /**
+   * Returns the current generation stamp
+   */
+  public long getStamp() {
+    return this.genstamp;
+  }
+
+  /**
+   * Sets the current generation stamp
+   */
+  public void setStamp(long stamp) {
+    this.genstamp = stamp;
+  }
+
+  /**
+   * Returns the current stamp and incrments the counter
+   */
+  public long nextStamp() {
+    this.genstamp++;
+    return this.genstamp;
+  }
+
+  /////////////////////////////////////
+  // Writable
+  /////////////////////////////////////
+  public void write(DataOutput out) throws IOException {
+    out.writeLong(genstamp);
+  }
+
+  public void readFields(DataInput in) throws IOException {
+    this.genstamp = in.readLong();
+    if (this.genstamp < 0) {
+      throw new IOException("Bad Generation Stamp: " + this.genstamp);
+    }
+  }
+
+  /////////////////////////////////////
+  // Comparable
+  /////////////////////////////////////
+  public int compareTo(Object o) {
+    GenerationStamp b = (GenerationStamp) o;
+    if (genstamp < b.genstamp) {
+      return -1;
+    } else if (genstamp == b.genstamp) {
+      return 0;
+    } else {
+      return 1;
+    }
+  }
+  public boolean equals(Object o) {
+    if (!(o instanceof GenerationStamp)) {
+      return false;
+    }
+    return genstamp == ((GenerationStamp)o).genstamp;
+  }
+    
+  public int hashCode() {
+    return 37 * 17 + (int) (genstamp^(genstamp>>>32));
+  }
+}