Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/21193#discussion_r186617171
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/javaCode.scala
---
@@ -114,19 +114,128 @@ object JavaCode {
}
}
+/**
+ * A trait representing a block of java code.
+ */
+trait Block extends JavaCode {
+
+ // The expressions to be evaluated inside this block.
+ def exprValues: Seq[ExprValue]
+
+ // Returns java code string for this code block.
+ override def toString: String = _marginChar match {
+ case Some(c) => code.stripMargin(c).trim
+ case _ => code.trim
+ }
+
+ // The leading prefix that should be stripped from each line.
+ // By default we strip blanks or control characters followed by '|' from
the line.
+ var _marginChar: Option[Char] = Some('|')
+
+ def stripMargin(c: Char): this.type = {
+ _marginChar = Some(c)
+ this
+ }
+
+ def stripMargin: this.type = {
+ _marginChar = Some('|')
+ this
+ }
+
+ // Concatenates this block with other block.
+ def + (other: Block): Block
+}
+
+object Block {
+
+ val CODE_BLOCK_BUFFER_LENGTH: Int = 512
+
+ implicit def blocksToBlock(blocks: Seq[Block]): Block = Blocks(blocks)
+
+ implicit class BlockHelper(val sc: StringContext) extends AnyVal {
+ def code(args: Any*): Block = {
+ sc.checkLengths(args)
+ if (sc.parts.length == 0) {
+ EmptyBlock
+ } else {
+ args.foreach {
+ case _: ExprValue =>
+ case _: Int | _: Long | _: Float | _: Double | _: String =>
+ case _: Block =>
+ case other => throw new IllegalArgumentException(
+ s"Can not interpolate ${other.getClass.getName} into code
block.")
+ }
+ CodeBlock(sc.parts, args)
+ }
+ }
+ }
+}
+
+/**
+ * A block of java code. Including a sequence of code parts and some
inputs to this block.
+ * The actual java code is generated by embedding the inputs into the code
parts.
+ */
+case class CodeBlock(codeParts: Seq[String], blockInputs: Seq[Any])
extends Block {
+ override def exprValues: Seq[ExprValue] = {
+ blockInputs.flatMap {
+ case b: Block => b.exprValues
+ case e: ExprValue => Seq(e)
+ case _ => Seq.empty
+ }
+ }
+
+ override def code: String = {
+ val strings = codeParts.iterator
+ val inputs = blockInputs.iterator
+ val buf = new StringBuilder(Block.CODE_BLOCK_BUFFER_LENGTH)
+ buf append StringContext.treatEscapes(strings.next)
+ while (strings.hasNext) {
+ buf append inputs.next
+ buf append StringContext.treatEscapes(strings.next)
+ }
+ buf.toString
+ }
+
+ override def + (other: Block): Block = other match {
+ case c: CodeBlock => Blocks(Seq(this, c))
+ case b: Blocks => Blocks(Seq(this) ++ b.blocks)
+ case EmptyBlock => this
+ }
+}
+
+case class Blocks(blocks: Seq[Block]) extends Block {
+ override def exprValues: Seq[ExprValue] = blocks.flatMap(_.exprValues)
+ override def code: String = blocks.map(_.toString).mkString("\n")
+
+ override def + (other: Block): Block = other match {
+ case c: CodeBlock => Blocks(blocks :+ c)
+ case b: Blocks => Blocks(blocks ++ b.blocks)
+ case EmptyBlock => this
+ }
+}
+
+object EmptyBlock extends Block with Serializable {
+ override def code: String = ""
+ override def exprValues: Seq[ExprValue] = Seq.empty
+
+ override def + (other: Block): Block = other
+}
+
/**
* A typed java fragment that must be a valid java expression.
*/
trait ExprValue extends JavaCode {
def javaType: Class[_]
def isPrimitive: Boolean = javaType.isPrimitive
+
+ // This will be called during string interpolation.
+ override def toString: String = ExprValue.exprValueToString(this)
--- End diff --
why is it needed? `JavaCode` already defines `override def toString: String
= code`
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