Github user wangyum commented on a diff in the pull request:
https://github.com/apache/spark/pull/18019#discussion_r117623979
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/stringExpressions.scala
---
@@ -1268,6 +1268,51 @@ case class Ascii(child: Expression) extends
UnaryExpression with ImplicitCastInp
}
/**
+ * Returns the ASCII character having the binary equivalent to n.
+ * If n is larger than 256 the result is equivalent to chr(n % 256)
+ */
+// scalastyle:off line.size.limit
+@ExpressionDescription(
+ usage = "_FUNC_(expr) - Returns the ASCII character having the binary
equivalent to `expr`. If n is larger than 256 the result is equivalent to chr(n
% 256)",
+ extended = """
+ Examples:
+ > SELECT _FUNC_(65);
+ A
+ """)
+// scalastyle:on line.size.limit
+case class Chr(child: Expression) extends UnaryExpression with
ImplicitCastInputTypes {
+
+ override def dataType: DataType = StringType
+ override def inputTypes: Seq[DataType] = Seq(LongType)
+
+ protected override def nullSafeEval(lon: Any): Any = {
+ val longVal = lon.asInstanceOf[Long]
+ if (longVal < 0) {
+ UTF8String.EMPTY_UTF8
+ } else if ((longVal & 0xFF) == 0) {
+ UTF8String.fromString(Character.MIN_VALUE.toString)
+ } else {
+ UTF8String.fromString((longVal & 0xFF).toChar.toString)
+ }
+ }
+
+ override def doGenCode(ctx: CodegenContext, ev: ExprCode): ExprCode = {
+ nullSafeCodeGen(ctx, ev, lon => {
+ s"""
+ if ($lon < 0) {
+ ${ev.value} = UTF8String.EMPTY_UTF8;
+ } else if (($lon & 0xFF) == 0) {
+ ${ev.value} =
UTF8String.fromString(String.valueOf(Character.MIN_VALUE));
+ } else {
+ char c = (char)($lon & 0xFF);
+ ${ev.value} = UTF8String.fromString(String.valueOf(c));
--- End diff --
It seems difficult to create the bytes directly from char,
`ByteBuffer.allocate(2).putChar(ch).array()` or `new byte[] { (byte)(ch &
0xff), (byte)(ch >> 8 & 0xff) }` not always equals to
`String.valueOf(ch).getBytes()`.
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