/**
* 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.ql.udf;
import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDF;
import org.apache.hadoop.io.Text;
/**
* UDFUnhex.
*
*/
@Description(name = "unhex",
value = "_FUNC_(str) - Converts hexadecimal argument to binary",
extended = "Performs the inverse operation of HEX(str). That is, it interprets\n"
+ "each pair of hexadecimal digits in the argument as a number and\n"
+ "converts it to the byte representation of the number. The\n"
+ "resulting characters are returned as a binary string.\n\n"
+ "Example:\n"
+ "> SELECT DECODE(UNHEX('4D7953514C'), 'UTF-8') from src limit 1;\n"
+ "'MySQL'\n\n"
+ "The characters in the argument string must be legal hexadecimal\n"
+ "digits: '0' .. '9', 'A' .. 'F', 'a' .. 'f'. If UNHEX() encounters\n"
+ "any nonhexadecimal digits in the argument, it returns NULL. Also,\n"
+ "if there are an odd number of characters a leading 0 is appended.")
public class UDFUnhex extends UDF {
/**
* Convert every two hex digits in s into.
*
*/
public byte[] evaluate(Text s) {
if (s == null) {
return null;
}
// append a leading 0 if needed
String str;
if (s.getLength() % 2 == 1) {
str = "0" + s.toString();
} else {
str = s.toString();
}
byte[] result = new byte[str.length() / 2];
for (int i = 0; i < str.length(); i += 2) {
try {
result[i / 2] = ((byte) Integer.parseInt(str.substring(i, i + 2), 16));
} catch (NumberFormatException e) {
// invalid character present, return null
return null;
}
}
return result;
}
}