org.apache.hadoop.hive.common.StringableMap Maven / Gradle / Ivy

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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.hive.common;


import java.util.HashMap;
import java.util.Map;
import java.util.Properties;

/**
 * A utility class that can convert a HashMap of Properties into a colon separated string,
 * and can take the same format of string and convert it to a HashMap of Properties.
 */
public class StringableMap extends HashMap {

  public StringableMap(String s) {
    String[] parts = s.split(":", 2);
    // read that many chars
    int numElements = Integer.parseInt(parts[0]);
    s = parts[1];
    for (int i = 0; i < numElements; i++) {
      // Get the key String.
      parts = s.split(":", 2);
      int len = Integer.parseInt(parts[0]);             
      String key = "";     // Default is now an empty string.

      if (len > 0) key = parts[1].substring(0, len);    
      // Please check the toString() method of this class.
      // null has -1 as length and empty String has 0.
      else if (len < 0) {
    	  key = null;
    	  len = 0;         // Set 0 to 'len' for null-valued key 
    	                   // since only len exists for null-valued key from the given String "s".     
      }
      
      // Get the value String for the key
      parts = parts[1].substring(len).split(":", 2);
      len = Integer.parseInt(parts[0]);
      String value = "";

      if (len > 0) value = parts[1].substring(0, len);
      else if (len < 0) {
    	  value = null; 
    	  len = 0;        // Set 0 to 'len' since only len exists.
      }
      
      // Put the entry into the HashMap.
      put(key, value);
      
      // Move to the next substring to process.
      s = parts[1].substring(len);
    }
  }

  public StringableMap(Map m) {
    super(m);
  }

  @Override
  public String toString() {
    StringBuilder buf = new StringBuilder();
    buf.append(size());
    buf.append(':');
    if (size() > 0) {
      for (Map.Entry entry : entrySet()) {
      	// Append the key String to the output StringBuilder.
        // Note that null is saved as -1 in length, and that empty String as 0.
      	int length = (entry.getKey() == null) ? -1 : entry.getKey().length();
      	buf.append(length);
        buf.append(':');
        if (length > 0) buf.append(entry.getKey());
        
        // Append the value String to the output StringBuilder.
        // Note that null is saved as -1 in length, and that empty String as 0.
        length = (entry.getValue() == null) ? -1 : entry.getValue().length();
        buf.append(length);
        buf.append(':');
        if (length > 0) {
        	buf.append(entry.getValue());
        }
      }
    }
    return buf.toString();
  }

  public Properties toProperties() {
    Properties props = new Properties();
    props.putAll(this);
    return props;
  }
}