use checkInputTypes

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/math.scala

@@ -18,10 +18,8 @@
 package org.apache.spark.sql.catalyst.expressions
 
 import java.lang.{Long => JLong}
-import java.nio.charset.{StandardCharsets, Charset}
 import java.util.Arrays
 
-import org.apache.commons.codec.DecoderException
 import org.apache.spark.sql.catalyst.analysis.TypeCheckResult
 import org.apache.spark.sql.catalyst.expressions.codegen._
 import org.apache.spark.sql.types._
@@ -361,27 +359,43 @@ case class Pow(left: Expression, right: Expression)
  * Resulting characters are returned as a byte array.
  */
 case class UnHex(child: Expression)
-  extends UnaryExpression with AutoCastInputTypes with Serializable  {
-
-  override def expectedChildTypes: Seq[DataType] = Seq(StringType)
+  extends UnaryExpression with Serializable  {
 
   override def dataType: DataType = BinaryType
 
+  override def checkInputDataTypes(): TypeCheckResult = {
+    if (child.dataType.isInstanceOf[StringType] || child.dataType == NullType) {
+      TypeCheckResult.TypeCheckSuccess
+    } else {
+      TypeCheckResult.TypeCheckFailure(s"$unHex accepts String type, not ${child.dataType}")
+    }
+  }
+
+
   override def eval(input: InternalRow): Any = {
     val num = child.eval(input)
     if (num == null) {
       null
     } else {
-      unhex(num.asInstanceOf[UTF8String])
+      unhex(num.asInstanceOf[UTF8String].toString)
     }
   }
 
-  private def unhex(utf8Str: UTF8String): Array[Byte] = {
-    try {
-      new org.apache.commons.codec.binary.Hex(StandardCharsets.UTF_8).decode(utf8Str.getBytes)
-    } catch {
-      case _: DecoderException => null
+  private def unhex(s: String): Array[Byte] = {
+    // append a leading 0 if needed
+    val str = if (s.length % 2 == 1) {"0" + s} else {s}
+    val result = new Array[Byte](str.length / 2)
+    var i = 0
+    while (i < str.length()) {
+      try {
+        result(i / 2) = Integer.parseInt(str.substring(i, i + 2), 16).asInstanceOf[Byte]
+      } catch {
+        // invalid character present, return null
+        case _: NumberFormatException => return null
+      }
+      i += 2
     }
+    result
   }
 }