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package scala.tools.nsc.interactive
import Lexer._
import java.io.Writer
import scala.language.implicitConversions
import scala.reflect.ClassTag
/** An abstract class for writing and reading Scala objects to and
* from a legible representation. The presesentation follows the following grammar:
* {{{
* Pickled = `true` | `false` | `null` | NumericLit | StringLit |
* Labelled | Pickled `,` Pickled
* Labelled = StringLit `(` Pickled? `)`
* }}}
*
* All ...Lit classes are as in JSON. @see scala.tools.nsc.io.Lexer
*
* Subclasses of `Pickler` each can write and read individual classes
* of values.
*
* @tparam T the type of values handled by this pickler.
*
* These Picklers build on the work of Andrew Kennedy. They are most closely inspired by
* Iulian Dragos' picklers for Scala to XML. See:
*
*
* http://code.google.com/p/gdata-scala-client/wiki/DevelopersGuide
*
*/
abstract class Pickler[T] {
import Pickler._
/** Writes value in pickled form
* @param wr the writer to which pickled form is written
* @param x the value to write
*/
def pickle(wr: Writer, x: T)
/** Reads value from pickled form.
*
* @param rd the lexer from which lexemes are read
* @return An `UnpickleSuccess value if the current input corresponds to the
* kind of value that is unpickled by the current subclass of `Pickler`,
* an `UnpickleFailure` value otherwise.
* @throws `Lexer.MalformedInput` if input is invalid, or if
* an `Unpickle
*/
def unpickle(rd: Lexer): Unpickled[T]
/** A pickler representing a `~`-pair of values as two consecutive pickled
* strings, separated by a comma.
* @param that the second pickler which together with the current pickler makes
* up the pair `this ~ that` to be pickled.
*/
def ~ [U] (that: => Pickler[U]): Pickler[T ~ U] = seqPickler(this, that)
/** A pickler that adds a label to the current pickler, using the representation
* `label ( )`
*
* @label the string to be added as a label.
*/
def labelled(label: String): Pickler[T] = labelledPickler(label, this)
/** A pickler obtained from the current pickler by a pair of transformer functions
* @param in the function that maps values handled by the current pickler to
* values handled by the wrapped pickler.
* @param out the function that maps values handled by the wrapped pickler to
* values handled by the current pickler.
*/
def wrapped [U] (in: T => U)(out: U => T): Pickler[U] = wrappedPickler(this)(in)(out)
/** A conditional pickler obtained from the current pickler.
* @param p the condition to test to find out whether pickler can handle
* some Scala value.
*/
def cond(p: Any => Boolean): CondPickler[T] = conditionalPickler(this, p)
/** A conditional pickler handling values of some Scala class. It adds the
* class name as a label to the representation of the current pickler and
* @param c the class of values handled by this pickler.
*/
def asClass[U <: T](c: Class[U]): CondPickler[T] = this.labelled(c.getName).cond(c isInstance _)
}
object Pickler {
/** A base class representing unpickler result. It has two subclasses:
* `UnpickleSucess` for successful unpicklings and `UnpickleFailure` for failures,
* where a value of the given type `T` could not be unpickled from input.
* @tparam T the type of unpickled values in case of success.
*/
abstract class Unpickled[+T] {
/** Transforms success values to success values using given function,
* leaves failures alone
* @param f the function to apply.
*/
def map[U](f: T => U): Unpickled[U] = this match {
case UnpickleSuccess(x) => UnpickleSuccess(f(x))
case f: UnpickleFailure => f
}
/** Transforms success values to successes or failures using given function,
* leaves failures alone.
* @param f the function to apply.
*/
def flatMap[U](f: T => Unpickled[U]): Unpickled[U] = this match {
case UnpickleSuccess(x) => f(x)
case f: UnpickleFailure => f
}
/** Tries alternate expression if current result is a failure
* @param alt the alternate expression to be tried in case of failure
*/
def orElse[U >: T](alt: => Unpickled[U]): Unpickled[U] = this match {
case UnpickleSuccess(x) => this
case f: UnpickleFailure => alt
}
/** Transforms failures into thrown `MalformedInput` exceptions.
* @throws MalformedInput if current result is a failure
*/
def requireSuccess: UnpickleSuccess[T] = this match {
case s @ UnpickleSuccess(x) => s
case f: UnpickleFailure =>
throw new MalformedInput(f.rd, "Unrecoverable unpickle failure:\n"+f.errMsg)
}
}
/** A class representing successful unpicklings
* @tparam T the type of the unpickled value
* @param result the unpickled value
*/
case class UnpickleSuccess[+T](result: T) extends Unpickled[T]
/** A class representing unpickle failures
* @param msg an error message describing what failed.
* @param rd the lexer unpickled values were read from (can be used to get
* error position, for instance).
*/
class UnpickleFailure(msg: => String, val rd: Lexer) extends Unpickled[Nothing] {
def errMsg = msg
override def toString = "Failure at "+rd.tokenPos+":\n"+msg
}
private def errorExpected(rd: Lexer, msg: => String) =
new UnpickleFailure("expected: "+msg+"\n" +
"found : "+rd.token,
rd)
private def nextSuccess[T](rd: Lexer, result: T) = {
rd.nextToken()
UnpickleSuccess(result)
}
/** The implicit `Pickler` value for type `T`. Equivalent to `implicitly[Pickler[T]]`.
*/
def pkl[T: Pickler] = implicitly[Pickler[T]]
/** A class represenenting `~`-pairs */
case class ~[+S, +T](fst: S, snd: T)
/** A wrapper class to be able to use `~` s an infix method */
implicit class TildeDecorator[S](x: S) {
/** Infix method that forms a `~`-pair. */
def ~ [T](y: T): S ~ T = new ~ (x, y)
}
/** Same as `p.labelled(label)`.
*/
def labelledPickler[T](label: String, p: Pickler[T]): Pickler[T] = new Pickler[T] {
def pickle(wr: Writer, x: T) = {
wr.write(quoted(label))
wr.write("(")
p.pickle(wr, x)
wr.write(")")
}
def unpickle(rd: Lexer): Unpickled[T] =
rd.token match {
case StringLit(`label`) =>
rd.nextToken()
rd.accept('(')
val result = p.unpickle(rd).requireSuccess
rd.accept(')')
result
case _ =>
errorExpected(rd, quoted(label)+"(...)")
}
}
/** Same as `p.wrap(in)(out)`
*/
def wrappedPickler[S, T](p: Pickler[S])(in: S => T)(out: T => S) = new Pickler[T] {
def pickle(wr: Writer, x: T) = p.pickle(wr, out(x))
def unpickle(rd: Lexer) = p.unpickle(rd) map in
}
/** Same as `p.cond(condition)`
*/
def conditionalPickler[T](p: Pickler[T], condition: Any => Boolean) = new CondPickler[T](condition) {
def pickle(wr: Writer, x: T) = p.pickle(wr, x)
def unpickle(rd: Lexer) = p.unpickle(rd)
}
/** Same as `p ~ q`
*/
def seqPickler[T, U](p: Pickler[T], q: => Pickler[U]) = new Pickler[T ~ U] {
lazy val qq = q
def pickle(wr: Writer, x: T ~ U) = {
p.pickle(wr, x.fst)
wr.write(',')
q.pickle(wr, x.snd)
}
def unpickle(rd: Lexer) =
for (x <- p.unpickle(rd); y <- { rd.accept(','); qq.unpickle(rd).requireSuccess })
yield x ~ y
}
/** Same as `p | q`
*/
def eitherPickler[T, U <: T, V <: T](p: CondPickler[U], q: => CondPickler[V]) =
new CondPickler[T](x => p.canPickle(x) || q.canPickle(x)) {
lazy val qq = q
override def tryPickle(wr: Writer, x: Any): Boolean =
p.tryPickle(wr, x) || qq.tryPickle(wr, x)
def pickle(wr: Writer, x: T) =
require(tryPickle(wr, x),
"no pickler found for "+x+" of class "+x.getClass.getName)
def unpickle(rd: Lexer) = p.unpickle(rd) orElse qq.unpickle(rd)
}
/** A conditional pickler for singleton objects. It represents these
* with the object's underlying class as a label.
* Example: Object scala.None would be represented as `scala.None$()`.
*/
def singletonPickler[T <: AnyRef](x: T): CondPickler[T] =
unitPickler
.wrapped { _ => x } { x => () }
.labelled (x.getClass.getName)
.cond (x eq _.asInstanceOf[AnyRef])
/** A pickler the handles instances of classes that have an empty constructor.
* It represents than as `$new ( )`.
* When unpickling, a new instance of the class is created using the empty
* constructor of the class via `Class.forName().newInstance()`.
*/
def javaInstancePickler[T <: AnyRef]: Pickler[T] =
(stringPickler labelled "$new")
.wrapped { name => Class.forName(name).newInstance().asInstanceOf[T] } { _.getClass.getName }
/** A picklers that handles iterators. It pickles all values
* returned by an iterator separated by commas.
* When unpickling, it always returns an `UnpickleSuccess` containing an iterator.
* This iterator returns 0 or more values that are obtained by unpickling
* until a closing parenthesis, bracket or brace or the end of input is encountered.
*
* This means that iterator picklers should not be directly followed by `~`
* because the pickler would also read any values belonging to the second
* part of the `~`-pair.
*
* What's usually done instead is that the iterator pickler is wrapped and labelled
* to handle other kinds of sequences.
*/
implicit def iterPickler[T: Pickler]: Pickler[Iterator[T]] = new Pickler[Iterator[T]] {
lazy val p = pkl[T]
def pickle(wr: Writer, xs: Iterator[T]) {
var first = true
for (x <- xs) {
if (first) first = false else wr.write(',')
p.pickle(wr, x)
}
}
def unpickle(rd: Lexer): Unpickled[Iterator[T]] = UnpickleSuccess(new Iterator[T] {
var first = true
def hasNext = {
val t = rd.token
t != EOF && t != RParen && t != RBrace && t != RBracket
}
def next(): T = {
if (first) first = false else rd.accept(',')
p.unpickle(rd).requireSuccess.result
}
})
}
/** A pickler that handles values that can be represented as a single token.
* @param kind the kind of token representing the value, used in error messages
* for unpickling.
* @param matcher A partial function from tokens to handled values. Unpickling
* succeeds if the matcher function is defined on the current token.
*/
private def tokenPickler[T](kind: String)(matcher: PartialFunction[Token, T]) = new Pickler[T] {
def pickle(wr: Writer, x: T) = wr.write(x.toString)
def unpickle(rd: Lexer) =
if (matcher isDefinedAt rd.token) nextSuccess(rd, matcher(rd.token))
else errorExpected(rd, kind)
}
/** A pickler for values of type `Long`, represented as integer literals */
implicit val longPickler: Pickler[Long] =
tokenPickler("integer literal") { case IntLit(s) => s.toLong }
/** A pickler for values of type `Int`, represented as integer literals */
implicit val intPickler: Pickler[Int] = longPickler.wrapped { _.toInt } { _.toLong }
/** A conditional pickler for the boolean value `true` */
private val truePickler =
tokenPickler("boolean literal") { case TrueLit => true } cond { _ == true }
/** A conditional pickler for the boolean value `false` */
private val falsePickler =
tokenPickler("boolean literal") { case FalseLit => false } cond { _ == false }
/** A pickler for values of type `Boolean`, represented as the literals `true` or `false`. */
implicit def booleanPickler: Pickler[Boolean] = truePickler | falsePickler
/** A pickler for values of type `Unit`, represented by the empty character string */
implicit val unitPickler: Pickler[Unit] = new Pickler[Unit] {
def pickle(wr: Writer, x: Unit) {}
def unpickle(rd: Lexer): Unpickled[Unit] = UnpickleSuccess(())
}
/** A pickler for values of type `String`, represented as string literals */
implicit val stringPickler: Pickler[String] = new Pickler[String] {
def pickle(wr: Writer, x: String) = wr.write(if (x == null) "null" else quoted(x))
def unpickle(rd: Lexer) = rd.token match {
case StringLit(s) => nextSuccess(rd, s)
case NullLit => nextSuccess(rd, null)
case _ => errorExpected(rd, "string literal")
}
}
/** A pickler for pairs, represented as `~`-pairs */
implicit def tuple2Pickler[T1: Pickler, T2: Pickler]: Pickler[(T1, T2)] =
(pkl[T1] ~ pkl[T2])
.wrapped { case x1 ~ x2 => (x1, x2) } { case (x1, x2) => x1 ~ x2 }
.labelled ("tuple2")
/** A pickler for 3-tuples, represented as `~`-tuples */
implicit def tuple3Pickler[T1, T2, T3](implicit p1: Pickler[T1], p2: Pickler[T2], p3: Pickler[T3]): Pickler[(T1, T2, T3)] =
(p1 ~ p2 ~ p3)
.wrapped { case x1 ~ x2 ~ x3 => (x1, x2, x3) } { case (x1, x2, x3) => x1 ~ x2 ~ x3 }
.labelled ("tuple3")
/** A pickler for list values */
implicit def listPickler[T: Pickler]: Pickler[List[T]] =
iterPickler[T] .wrapped { _.toList } { _.iterator } .labelled ("scala.List")
}
/** A subclass of Pickler can indicate whether a particular value can be pickled by instances
* of this class.
* @param canPickle The predicate that indicates whether a given value
* can be pickled by instances of this class.
*/
abstract class CondPickler[T](val canPickle: Any => Boolean) extends Pickler[T] {
import Pickler._
/** Pickles given value `x` if possible, as indicated by `canPickle(x)`.
*/
def tryPickle(wr: Writer, x: Any): Boolean = {
val result = canPickle(x)
if (result) pickle(wr, x.asInstanceOf[T])
result
}
/** A pickler obtained from this pickler and an alternative pickler.
* To pickle a value, this pickler is tried first. If it cannot handle
* the object (as indicated by its `canPickle` test), then the
* alternative pickler is tried.
* To unpickle a value, this unpickler is tried first. If it cannot read
* the input (as indicated by a `UnpickleFailure` result), then the
* alternative pickler is tried.
* @tparam V The handled type of the returned pickler.
* @tparam U The handled type of the alternative pickler.
* @param that The alternative pickler.
*/
def | [V >: T, U <: V] (that: => CondPickler[U]): CondPickler[V] =
eitherPickler[V, T, U](this, that)
}