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/**
 * 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.fs.permission;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.io.*;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;

/**
 * Store permission related information.
 */
@InterfaceAudience.LimitedPrivate({"HDFS", "MapReduce"})
@InterfaceStability.Unstable
public class PermissionStatus implements Writable {
  static final WritableFactory FACTORY = new WritableFactory() {
    @Override
    public Writable newInstance() { return new PermissionStatus(); }
  };
  static {                                      // register a ctor
    WritableFactories.setFactory(PermissionStatus.class, FACTORY);
  }

  /**
   * Create an immutable {@link PermissionStatus} object.
   * @param user user.
   * @param group group.
   * @param permission permission.
   * @return PermissionStatus.
   */
  public static PermissionStatus createImmutable(
      String user, String group, FsPermission permission) {
    return new PermissionStatus(user, group, permission) {
      @Override
      public void readFields(DataInput in) throws IOException {
        throw new UnsupportedOperationException();
      }
    };
  }

  private String username;
  private String groupname;
  private FsPermission permission;

  private PermissionStatus() {}

  /**
   * Constructor.
   *
   * @param user user.
   * @param group group.
   * @param permission permission.
   */
  public PermissionStatus(String user, String group, FsPermission permission) {
    username = user;
    groupname = group;
    this.permission = permission;
  }

  /**
   * Return user name.
   * @return user name.
   */
  public String getUserName() {return username;}

  /**
   * Return group name.
   * @return group name.
   */
  public String getGroupName() {return groupname;}

  /**
   * Return permission.
   * @return FsPermission.
   */
  public FsPermission getPermission() {return permission;}

  @Override
  public void readFields(DataInput in) throws IOException {
    username = Text.readString(in, Text.DEFAULT_MAX_LEN);
    groupname = Text.readString(in, Text.DEFAULT_MAX_LEN);
    permission = FsPermission.read(in);
  }

  @Override
  public void write(DataOutput out) throws IOException {
    write(out, username, groupname, permission);
  }

  /**
   * Create and initialize a {@link PermissionStatus} from {@link DataInput}.
   * @param in data input.
   * @throws IOException raised on errors performing I/O.
   * @return PermissionStatus.
   */
  public static PermissionStatus read(DataInput in) throws IOException {
    PermissionStatus p = new PermissionStatus();
    p.readFields(in);
    return p;
  }

  /**
   * Serialize a {@link PermissionStatus} from its base components.
   * @param out out.
   * @param username username.
   * @param groupname groupname.
   * @param permission FsPermission.
   * @throws IOException raised on errors performing I/O.
   */
  public static void write(DataOutput out,
                           String username, 
                           String groupname,
                           FsPermission permission) throws IOException {
    Text.writeString(out, username, Text.DEFAULT_MAX_LEN);
    Text.writeString(out, groupname, Text.DEFAULT_MAX_LEN);
    permission.write(out);
  }

  @Override
  public String toString() {
    return username + ":" + groupname + ":" + permission;
  }
}