1 files changed, 84 insertions, 0 deletions
diff --git a/src/main/scala/firrtl/annotations/JsonProtocol.scala b/src/main/scala/firrtl/annotations/JsonProtocol.scala
new file mode 100644
index 00000000..5005ccb0
--- /dev/null
+++ b/src/main/scala/firrtl/annotations/JsonProtocol.scala
@@ -0,0 +1,84 @@
+
+package firrtl
+package annotations
+
+import scala.util.Try
+
+import org.json4s._
+import org.json4s.native.JsonMethods._
+import org.json4s.native.Serialization
+import org.json4s.native.Serialization.{read, write, writePretty}
+
+import firrtl.ir._
+import firrtl.Utils.error
+
+object JsonProtocol {
+
+  // Helper for error messages
+  private def prettifyJsonInput(in: JsonInput): String = {
+    def defaultToString(base: String, obj: Any): String = s"$base@${obj.hashCode.toHexString}"
+    in match {
+      case FileInput(file) => file.toString
+      case StringInput(o) => defaultToString("String", o)
+      case ReaderInput(o) => defaultToString("Reader", o)
+      case StreamInput(o) => defaultToString("Stream", o)
+    }
+  }
+
+  class TransformClassSerializer extends CustomSerializer[Class[_ <: Transform]](format => (
+    { case JString(s) => Class.forName(s).asInstanceOf[Class[_ <: Transform]] },
+    { case x: Class[_] => JString(x.getName) }
+  ))
+  // TODO Reduce boilerplate?
+  class NamedSerializer extends CustomSerializer[Named](format => (
+    { case JString(s) => AnnotationUtils.toNamed(s) },
+    { case named: Named => JString(named.serialize) }
+  ))
+  class CircuitNameSerializer extends CustomSerializer[CircuitName](format => (
+    { case JString(s) => AnnotationUtils.toNamed(s).asInstanceOf[CircuitName] },
+    { case named: CircuitName => JString(named.serialize) }
+  ))
+  class ModuleNameSerializer extends CustomSerializer[ModuleName](format => (
+    { case JString(s) => AnnotationUtils.toNamed(s).asInstanceOf[ModuleName] },
+    { case named: ModuleName => JString(named.serialize) }
+  ))
+  class ComponentNameSerializer extends CustomSerializer[ComponentName](format => (
+    { case JString(s) => AnnotationUtils.toNamed(s).asInstanceOf[ComponentName] },
+    { case named: ComponentName => JString(named.serialize) }
+  ))
+
+  /** Construct Json formatter for annotations */
+  def jsonFormat(tags: Seq[Class[_ <: Annotation]]) = {
+    Serialization.formats(FullTypeHints(tags.toList)).withTypeHintFieldName("class") +
+      new TransformClassSerializer + new NamedSerializer + new CircuitNameSerializer +
+      new ModuleNameSerializer + new ComponentNameSerializer
+  }
+
+  /** Serialize annotations to a String for emission */
+  def serialize(annos: Seq[Annotation]): String = serializeTry(annos).get
+
+  def serializeTry(annos: Seq[Annotation]): Try[String] = {
+    val tags = annos.map(_.getClass).distinct
+    implicit val formats = jsonFormat(tags)
+    Try(writePretty(annos))
+  }
+
+  def deserialize(in: JsonInput): Seq[Annotation] = deserializeTry(in).get
+
+  def deserializeTry(in: JsonInput): Try[Seq[Annotation]] = Try({
+    def throwError() = throw new InvalidAnnotationFileException(prettifyJsonInput(in))
+    val parsed = parse(in)
+    val annos = parsed match {
+      case JArray(objs) => objs
+      case _ => throwError()
+    }
+    // Gather classes so we can deserialize arbitrary Annotations
+    val classes = annos.map({
+      case JObject(("class", JString(c)) :: tail) => c
+      case _ => throwError()
+    }).distinct
+    val loaded = classes.map(Class.forName(_).asInstanceOf[Class[_ <: Annotation]])
+    implicit val formats = jsonFormat(loaded)
+    read[List[Annotation]](in)
+  })
+}