Add firrtl.options

This adds a new package, "firrtl.options", that provides a framework for
working with options inside and outside FIRRTL.

Small changes:
  - Make TerminateOnExit return the correct exit code
  - Deprecate mutable TerminateOnExit
  - Add immutable DoNotTermianteOnExit

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

1 files changed, 27 insertions, 0 deletions

diff --git a/src/main/scala/firrtl/options/OptionsView.scala b/src/main/scala/firrtl/options/OptionsView.scala
new file mode 100644
index 00000000..dade5c56
--- /dev/null
+++ b/src/main/scala/firrtl/options/OptionsView.scala
@@ -0,0 +1,27 @@
+// See LICENSE for license details.
+
+package firrtl.options
+
+import firrtl.AnnotationSeq
+
+/** Type class defining a "view" of an [[AnnotationSeq]]
+  * @tparam T the type to which this viewer converts an [[AnnotationSeq]] to
+  */
+trait OptionsView[T] {
+
+  /** Convert an [[AnnotationSeq]] to some other type
+    * @param options some annotations
+    */
+  def view(options: AnnotationSeq): Option[T]
+}
+
+/** A shim to manage multiple "views" of an [[AnnotationSeq]] */
+object Viewer {
+
+  /** Convert annotations to options using an implicitly provided [[OptionsView]]
+    * @param options some annotations
+    * @param optionsView a converter of options to the requested type
+    * @tparam T the type to which the input [[AnnotationSeq]] should be viewed as
+    */
+  def view[T](options: AnnotationSeq)(implicit optionsView: OptionsView[T]): Option[T] = optionsView.view(options)
+}