org.tresql.parsing.MemParsers.scala Maven / Gradle / Ivy

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package org.tresql.parsing

trait MemParsers extends scala.util.parsing.combinator.Parsers {
  private val intermediateResults = new ThreadLocal[scala.collection.mutable.Map[(String, Int), ParseResult[_]]] {
    override def initialValue: scala.collection.mutable.Map[(String, Int), ParseResult[_]] =
      scala.collection.mutable.HashMap()
  }

  class MemParser[+T](underlying: Parser[T]) extends Parser[T] {
    def apply(in: Input) = intermediateResults.get.get(underlying.toString -> in.offset)
      .map(_.asInstanceOf[ParseResult[T]]).getOrElse {
        val r = underlying(in)
        intermediateResults.get += ((underlying.toString -> in.offset) -> r)
        r
      }
  }

  override def phrase[T](p: Parser[T]): Parser[T] = {
    val phrp = super.phrase(p)
    new Parser[T] {
      def apply(in: Input) = {
        try {
          intermediateResults.get.clear()
          phrp(in)
        } finally intermediateResults.get.clear()
      }
    }
  }

  implicit def parser2MemParser[T](parser: Parser[T]): MemParser[T] = new MemParser(parser)
}